H1-receptor antagonists: safety issues

Potential Anti-Amnesic Activity of a Novel Multimodal Derivative of Salicylamide, JJGW08, in Mice

Memory impairments constitute a significant problem worldwide, and the COVID-19 pandemic dramatically increased the prevalence of cognitive deficits. Patients with cognitive deficits, specifically memory disturbances, have underlying comorbid conditions such as schizophrenia, anxiety, or depression. Moreover, the available treatment options have unsatisfactory effectiveness. Therefore, there is a need to search for novel procognitive and anti-amnesic drugs with additional pharmacological activity. One of the important therapeutic targets involved in the modulation of learning and memory processes are serotonin receptors, including 5-HT1A, 5-HT6, and 5-HT7, which also play a role in the pathophysiology of depression. Therefore, this study aimed to assess the anti-amnesic and antidepressant-like potential of JJGW08, a novel arylpiperazine alkyl derivative of salicylamide with strong antagonistic properties at 5-HT1A and D2 receptors and weak at 5-HT2A and 5-HT7 receptors in rodents. First, we investigated the compound’s affinity for 5-HT6 receptors using the radioligand assays. Next, we assessed the influence of the compound on long-term emotional and recognition memory. Further, we evaluated whether the compound could protect against MK-801-induced cognitive impairments. Finally, we determined the potential antidepressant-like activity of the tested compound. We found that JJGW08 possessed no affinity for 5-HT6 receptors. Furthermore, JJGW08 protected mice against MK-801-induced recognition and emotional memory deficits but showed no antidepressant-like effects in rodents. Therefore, our preliminary study may suggest that blocking serotonin receptors, especially 5-HT1A and 5-HT7, might be beneficial in treating cognitive impairments, but it requires further investigation.

Diphenhydramine: Time to Move on?

Diphenhydramine is one of the most widely available, longest-used antihistamine medications but has many side effects including sedation and risk of toxicity in overdose including cardiac toxicity. It is frequently inappropriately used when newer, more favorable antihistamine medications are available. Second-generation antihistamines are also widely available and affordable, with many of the same desired effects as diphenhydramine and fewer, if any, of the undesirable side effects. Because of the negative side effects and wide availability of alternative antihistamine medications, it is definitively time to move on from diphenhydramine.

Potential Small Molecules for Therapy of Lupus Nephritis Based on Genetic Effect and Immune Infiltration

Lupus nephritis (LN) is the most common and significant complication of systemic lupus erythematosus (SLE) due to its poor prognosis and mortality rates in SLE patients. There is a critical need for new drugs as the pathogenesis of LN remains to be elucidated and immunosuppressive therapy comes with many deficiencies. In this study, 23 hub genes (IFI6, PLSCR1, XAF1, IFI16, IFI44, MX1, IFI44L, IFIT3, IFIT2, IFI27, DDX58, EIF2AK2, IFITM1, RTP4, IFITM3, TRIM22, PARP12, IFIH1, OAS1, HERC6, RSAD2, DDX60, and MX2) were identified through bioinformatics and network analysis and are closely related to interferon production and function. Interestingly, immune cell infiltration analysis and correlation analysis demonstrate a positive correlation between the expression of 23 hub genes and monocyte infiltration in glomeruli and M2 macrophage infiltration in the tubulointerstitium of LN patients. Additionally, the CTD database, DsigDB database, and DREIMT database were used to explore the bridging role of genes in chemicals and LN as well as the potential influence of these chemicals on immune cells. After comparison and discussion, six small molecules (Acetohexamide, Suloctidil, Terfenadine, Prochlorperazine, Mefloquine, and Triprolidine) were selected for their potential ability in treating lupus nephritis.

Desloratadine Exposure and Incidence of Seizure: A Nordic Post-authorization Safety Study Using a New-User Cohort Study Design, 2001-2015

Introduction

A small number of adverse events of seizure in patients using desloratadine (DL) have been reported. The European Medicines Agency requested a post-authorization safety study to investigate whether there is an association between DL exposure and seizure.

Objective

The aim was to study the association between DL exposure and incidence of first seizure.

Methods

A new-user cohort study of individuals redeeming a first-ever prescription of DL in Denmark, Finland, Norway, and Sweden in 2001–2015 was conducted. DL exposure was defined as days’ supply plus a 4-week grace period. DL unexposed periods were initiated 27 weeks after DL prescription redemption. Poisson regression was used to estimate the adjusted incidence rate and adjusted incidence rate ratio (aIRR) of incident seizure.

Results

A total of 1,807,347 first-ever DL users were included in the study, with 49.3% male and a mean age of 29.5 years at inclusion; 20.3% were children aged 0–5 years. The adjusted incidence rates of seizure were 21.7 and 31.6 per 100,000 person-years during DL unexposed and exposed periods, respectively. A 46% increased incidence rate of seizure was found during DL exposed periods (aIRR = 1.46, 95% confidence interval [CI] 1.34–1.59). The aIRR ranged from 1.85 (95% CI 1.65–2.08) in children aged 0–5 years to 1.01 in adults aged 20 years or more (95% CI 0.85–1.19).

Conclusion

This study found an increased incidence rate of seizure during DL exposed periods as compared to unexposed periods among individuals younger than 20 years. No difference in incidence rate of seizure was observed in adults between DL exposed and unexposed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40264-021-01106-7.

Could Histamine H1 Receptor Antagonists Be Used for Treating COVID-19?

COVID-19 has rapidly become a pandemic worldwide, causing extensive and long-term health issues. There is an urgent need to identify therapies that limit SARS-CoV-2 infection and improve the outcome of COVID-19 patients. Unbalanced lung inflammation is a common feature in severe COVID-19 patients; therefore, reducing lung inflammation can undoubtedly benefit the clinical manifestations. Histamine H1 receptor (H1 receptor) antagonists are widely prescribed medications to treat allergic diseases, while recently it has emerged that they show significant promise as anti-SARS-CoV-2 agents. Here, we briefly summarize the novel use of H1 receptor antagonists in combating SARS-CoV-2 infection. We also describe the potential antiviral mechanisms of H1 receptor antagonists on SARS-CoV-2. Finally, the opportunities and challenges of the use of H1 receptor antagonists in managing COVID-19 are discussed.

Hydroxyzine Use in Preschool Children and Its Effect on Neurodevelopment: A Population-Based Longitudinal Study

We identified the first-generation antihistamine hydroxyzine as the earliest and most frequently prescribed drug affecting the central nervous system in children under the age of 5 years in the province of British Columbia, Canada (1. 1% prevalence). Whereas, the antagonism of H1-receptors exerts anti-pruritic effects in atopic dermatitis and diaper rash, animal studies suggest an adverse association between reduced neurotransmission of histamine and psychomotor behavior. In order to investigate hydroxyzine safety, we characterized the longitudinal patterns of hydroxyzine use in children under the age of 5 years and determined mental- and psychomotor disorders up to the age of 10 years. We found significantly higher rates of ICD-9 and ICD-10 codes for disorders such as tics (307), anxiety (300) and disturbance of conduct (312) in frequent users of hydroxyzine. Specifically, repeat prescriptions of hydroxyzine compared to a single prescription show an increase in tic disorder, anxiety and disturbance of conduct by odds ratios of: 1.55 (95%CI: 1.23-1.96); 1.34 (95%CI: 1.05-1.70); and 1.34 (95%CI: 1.08-1.66) respectively in children up to the age of 10 years. Furthermore, a non-significant increased trend was found for ADHD (314) and disturbance of emotions (313). This is the first study reporting an association between long-term neurodevelopmental adverse effects and early use of hydroxyzine. Controlled studies are required in order to prove a causal relationship and to confirm the safety of hydroxyzine in the pediatric population. For the time being, we suggest the shortest possible duration for hydroxyzine use in preschool-age children.

From Antihistamine to Anti-infective: Loratadine Inhibition of Regulatory PASTA Kinases in Staphylococci Reduces Biofilm Formation and Potentiates β-Lactam Antibiotics and Vancomycin in Resistant Strains of Staphylococcus aureus

Staphylococcus epidermidis and Staphylococcus aureus are important human pathogens responsible for two-thirds of all postsurgical infections of indwelling medical devices. Staphylococci form robust biofilms that provide a reservoir for chronic infection, and antibiotic-resistant isolates are increasingly common in both healthcare and community settings. Novel treatments that can simultaneously inhibit biofilm formation and antibiotic-resistance pathways are urgently needed to combat the increasing rates of antibiotic-resistant infections. Herein we report that loratadine, an FDA-approved antihistamine, significantly inhibits biofilm formation in both S. aureus and S. epidermidis. Furthermore, loratadine potentiates β-lactam antibiotics in methicillin-resistant strains of S. aureus and potentiates both β-lactam antibiotics and vancomycin in vancomycin-resistant strains of S. aureus. Additionally, we elucidate loratadine's mechanism of action as a novel inhibitor of the regulatory PASTA kinases Stk and Stk1 in S. epidermidis and S. aureus, respectively. Finally, we describe how Stk1 inhibition affects the expression of genes involved in both biofilm formation and antibiotic resistance in S. epidermidis and S. aureus.

Drug-induced Proarrhythmia and Torsade de Pointes: A Primer for Students and Practitioners of Medicine and Pharmacy

Multiple marketing withdrawals due to proarrhythmic concerns occurred in the United States, Canada, and the United Kingdom in the late 1980s to early 2000s. This primer reviews the clinical implications of a drug's identified proarrhythmic liability, the issues associated with these safety-related withdrawals, and the actions taken by the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and by regulatory agencies in terms of changing drug development practices and introducing new nonclinical and clinical tests to asses proarrhythmic liability. ICH Guidelines S7B and E14 were released in 2005. Since then, they have been adopted by many regional regulatory authorities and have guided nonclinical and clinical proarrhythmic cardiac safety assessments during drug development. While this regulatory paradigm has been successful in preventing drugs with unanticipated potential for inducing the rare but potentially fatal polymorphic ventricular arrhythmia torsade de pointes from entering the market, it has led to the termination of drug development programs for other potentially useful medicines because of isolated results from studies with limited predictive value. Research efforts are now exploring alternative approaches to better predict potential proarrhythmic liabilities. For example, in the domain of human electrocardiographic assessments, concentration-response modeling conducted during phase 1 clinical development has recently become an accepted alternate primary methodology to the ICH E14 "thorough QT/QTc" study for defining a drug's corrected QT interval prolongation liability under certain conditions. When a drug's therapeutic benefit is considered important at a public health level but there is also an identified proarrhythmic liability that may result from administration of the single drug in certain individuals and/or drug-drug interactions, marketing approval will be accompanied by appropriate directions in the drug's prescribing information. Health-care professionals in the fields of medicine and pharmacy need to consider the prescribing information in conjunction with individual patients' clinical characteristics and concomitant medications when prescribing and dispensing such drugs.

The role and choice criteria of antihistamines in allergy management - expert opinion

Allergic diseases are the most common chronic conditions lasting throughout the patient’s life. They not only cause significant deterioration in the quality of life of patients but also lead to significant absenteeism and reduced productivity, resulting in very high costs for society. Effective and safe treatment of allergic diseases is therefore one of the main challenges for public health and should be carried out by all the specialists in family medicine, internists and paediatricians in collaboration with allergists, otorhinolaryngologists and dermatologists. Antihistamines are most commonly used in the treatment of allergies. Several dozen drugs are available on the pharmaceutical market, and their generic forms are advertised widely as very effective drugs for the treatment of allergic diseases. What is the truth? What are the data from clinical trials and observational studies? Are all drugs equally effective and safe for the patient? According to a panel of experts representing various fields of medicine, inappropriate treatment of allergies can be very risky for patients, and seemingly equally acting medications may differ greatly. Therefore, a panel of experts gathered the latest data from the entire scientific literature and analysed the latest standards and recommendations prepared by scientific societies. This paper provides a summary of these studies and highlights the importance for the patient of the proper choice of drug to treat his allergies.

Biodistribution of diphenhydramine in reproductive organs in an overdose case

Motion sickness medications such as Travelmin^® prescribed in Japan include diphenhydramine (DPH), dyphylline, diphenidol, and/or caffeine. Herein, we report a patient who died due to rhabdomyolysis after ingesting a DPH containing motion sickness medication. A Japanese male in his 30 s reported missing after going out for a drive early in the morning was found dead in his car in the evening of the same day. An autopsy showed moderate edema, congestion, and several petechiae in both lungs. The brain was congested and edematous with no atherosclerosis of cerebral arteries. The prostate and both testes were slightly edematous. Gastric contents included approximately 15 mL of dark-brown fluid without tablets or food residue. Toxicological examination showed that blood DPH levels in all tissues were between 4.90 and 7.27 μg/mL, which represented toxic to lethal levels. DPH (μg/mL) levels were approximately 3-9 times higher in the prostate (73.42) and testes (left, 28.23; right, 30.09) than those in all regions of the brain (range 7.75-12.33). Blood dyphylline, diphenidol and caffeine levels in reproductive organs reached high, but not toxic levels. In conclusion, DPH, dyphylline, diphenidol, and caffeine levels were higher in reproductive organs such as the prostate and testes than in the central nervous system and heart. As we determined in this case, motion sickness medications might accumulate in reproductive organs. Thus, further examination of tissue biodistribution of DPH, dyphylline, diphenidol, and caffeine is necessary to assess their potential long-term effects in these sites.

Clinical pharmacists' opportunities to reduce inappropriate prescription of QT-prolonging medications: calls to action

All biologically active agents carry the potential to lead to adverse reactions in certain individuals, including serious cardiac adverse reactions. Since 2005, there has been an international regulatory landscape governing the investigation of a new drug's propensity to lead to the polymorphic ventricular tachycardia Torsades de Pointes (Torsades), a rare but potentially fatal occurrence. When a regulatory agency considers it appropriate, warning information is placed in a medicine's patient information leaflet (label) concerning drug-induced QT interval prolongation, a phenomenon associated with Torsades. In busy hospital settings, however, prescribers, including cardiologists, make injudicious prescribing decisions that put patients at risk. The science of cardiac safety, including the clinical trials that generate the information about QT prolongation in patient information leaflets, is frequently not part of the curriculum at Schools of Pharmacy. Given that medication-induced cardiotoxicity is extremely serious, we advocate that schools integrate the science of cardiac safety into existing therapeutics/therapeutic medication monitoring courses. Given their expert knowledge of pharmacology, pharmacists working as part of a hospital's clinical team would then be even better placed to review prescribing decisions concerning medications that prolong the QT interval, and alert prescribers in cases where reassessing their decisions seems prudent. National pharmacy societies or other pertinent professional societies could create practice guidelines to support graduates once employed as clinical pharmacists. Clinical pharmacists are well placed to be influential arbiters of safer prescribing decisions. Cardiac safety education during their pharmacy training and practice guideline support from professional societies during their careers can optimize this role.

Treatment of allergic rhinitis and urticaria: a review of the newest antihistamine drug bilastine

Allergic rhinitis and urticaria are common allergic diseases that may have a major negative impact on patients' quality of life. Bilastine, a novel new-generation antihistamine that is highly selective for the H1 histamine receptor, has a rapid onset and prolonged duration of action. This agent does not interact with the cytochrome P450 system and does not undergo significant metabolism in humans, suggesting that it has very low potential for drug-drug interactions, and does not require dose adjustment in renal impairment. As bilastine is not metabolized and is excreted largely unchanged, hepatic impairment is not expected to increase systemic exposure above the drug's safety margin. Bilastine has demonstrated similar efficacy to cetirizine and desloratadine in patients with seasonal allergic rhinitis and, in a Vienna Chamber study, a potentially longer duration of action than fexofenadine in patients with asymptomatic seasonal allergic rhinitis. It has also shown significant efficacy (similar to that of cetirizine) and safety in the long-term treatment of perennial allergic rhinitis. Bilastine showed similar efficacy to levocetirizine in patients with chronic spontaneous urticaria and can be safely used at doses of up to fourfold higher than standard dosage (80 mg once daily). The fourfold higher than standard dose is specified as an acceptable second-line treatment option for urticaria in international guidelines. Bilastine is generally well tolerated, both at standard and at supratherapeutic doses, appears to have less sedative potential than other second-generation antihistamines, and has no cardiotoxicity. Based on its pharmacokinetic properties, efficacy, and tolerability profile, bilastine will be valuable in the management of allergic rhinitis and urticaria.

International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors

Histamine is a developmentally highly conserved autacoid found in most vertebrate tissues. Its physiological functions are mediated by four 7-transmembrane G protein-coupled receptors (H1R, H2R, H3R, H4R) that are all targets of pharmacological intervention. The receptors display molecular heterogeneity and constitutive activity. H1R antagonists are long known antiallergic and sedating drugs, whereas the H2R was identified in the 1970s and led to the development of H2R-antagonists that revolutionized stomach ulcer treatment. The crystal structure of ligand-bound H1R has rendered it possible to design new ligands with novel properties. The H3R is an autoreceptor and heteroreceptor providing negative feedback on histaminergic and inhibition on other neurons. A block of these actions promotes waking. The H4R occurs on immuncompetent cells and the development of anti-inflammatory drugs is anticipated.

Cherry-picked ligands at histamine receptor subtypes

Histamine, a biogenic amine, is considered as a principle mediator of multiple physiological effects through binding to its H1, H2, H3, and H4 receptors (H1-H4Rs). Currently, the HRs have gained attention as important targets for the treatment of several diseases and disorders ranging from allergy to Alzheimer's disease and immune deficiency. Accordingly, medicinal chemistry studies exploring histamine-like molecules and their physicochemical properties by binding and interacting with the four HRs has led to the development of a diversity of agonists and antagonists that display selectivity for each HR subtype. An overview on H1-R4Rs and developed ligands representing some key steps in development is provided here combined with a short description of structure-activity relationships for each class. Main chemical diversities, pharmacophores, and pharmacological profiles of most innovative H1-H4R agonists and antagonists are highlighted. Therefore, this overview should support the rational choice for the optimal ligand selection based on affinity, selectivity and efficacy data in biochemical and pharmacological studies. This article is part of the Special Issue entitled 'Histamine Receptors'.

Post-mortem evidence of doxylamine in toxicological analyses

BACKGROUND

Doxylamine (DA) is widely available in pharmacies without prescription and can be used in suicidal intention because of its sedative and anticholinergic properties. Research of literature shows that only a few publications deal with post-mortem evidence of DA and its interpretation during toxicological examination.

MATERIAL AND METHODS

In this study, all cases with a positive detection of DA during toxicological analyses with high-performance liquid chromatography in the time period 2000 to 2010 at the Institute of Legal Medicine and Forensic Sciences in Berlin, Germany were retrospectively analysed and interpreted, taking into account police investigations, autopsy results and toxicological analyses.

RESULTS

In total, 22 cases with DA intoxications were discovered (♂=16/♀=6, age-at-death range 17 to 90years). Maximum blood concentration was measured at 77.5μg/mL. Cause of death was due to DA intoxication in eight suicide cases; seven of those were combined intoxications (DA and other substances, particularly diphenhydramine). During the evaluated time period no monointoxications with DA were discovered.

CONCLUSION

Benchmarks published in past literature are meant as orientation during evaluation of post-mortem DA evidence. These should not be used as absolute values and need to be interpreted individually in each case. Post-mortem redistribution needs to be considered as a main factor in alteration of DA concentration measurement. Furthermore, proof of DA ingestion found in gastric content should only be interpreted quantitatively due to unreliable calculation of the ingested amount. In conclusion, a variety of factors, such as the time period between time of death and the time of the first toxicological analysis, the condition of the body and the findings at autopsy, must also be critically considered.

Update on the cardiac safety of moxifloxacin

Cardiac safety was compared in patients receiving moxifloxacin and other antimicrobials in a large patient population from Phase II-IV randomized active-controlled clinical trials. Moxifloxacin 400 mg once-daily monotherapy was administered orally (PO) or sequentially (intravenous/oral, IV/PO). Across 64 trials, 21,298 patients received PO therapy (10,613 moxifloxacin, 10,685 comparators) while 6846 received sequential IV/PO therapy (3431 moxifloxacin, 3415 comparators). Treatment-emergent cardiac adverse event (AE) rates were similar for moxifloxacin and comparators in PO (6.6% vs 5.8%) and IV/PO (11.0% vs 12.0%) trials. Treatment-emergent cardiac adverse drug reactions were rare in PO (moxifloxacin 3.2% vs comparators 2.4%) and IV/PO (moxifloxacin 1.4% vs comparators 1.5%) patients. There were five (<0.02%) treatment-emergent drug-related deaths due to cardiac events out of 28,144 patients; one PO patient died treated with comparators, one patient died treated with IV/PO moxifloxacin, and three patients died after treatment with IV/PO comparators. Only one case of treatment-related non-fatal torsade de pointes occurred in the comparator arm. Incidence rates of cardiac AEs remained low in populations at elevated risk of cardiac events predisposed to QTc prolongation (i.e. community-acquired pneumonia patients admitted to the intensive care unit and/or mechanical ventilation, patients with documented prolongation of baseline QTc interval, women, and patients ≥ 65 years old). There was no evidence of unexpected cardiac events. After moxifloxacin treatment, an expected small prolongation in QTcB and QTcF was found. This analysis of numerous clinical trials shows the favorable cardiac safety profile of moxifloxacin, when used appropriately and according to its label, versus other antibiotics.

Enhancement of B cell and monocyte populations in rats exposed to chlorpheniramine

Chlorpheniramine is an anti-histamine agent on IgE-mediated inflammation. In order to investigate the immunomodulatory effects of chlorpheniramine, we assessed the changes of peripheral mononuclear cell populations and other general clinical parameters, including hematology and clinical chemistry, following chlorpheniramine administration in rats. Since prednisolone is commonly co-prescribed with anti-histamine in many hypersensitive reactions, we also examined the changes to compare the results after the prednisolone administration. Chlorpheniramine (50, 100 and 200 μg/kg) and prednisolone (1, 2 and 4 mg/kg) were intramuscularly administered to female Sprague-Dawley (SD) rats 3 times, at intervals of 1 week. Except the clinical signs, such as stiffness and abnormal gait due to the local toxicity at injection sites, no other significant changes in body weights, urinalysis, and macroscopic examination were noted in the animals given chlorpheniramine. On the other hand, white blood cells, especially B cells and monocytes, showed a dose-dependent increase in the chlorpheniramine-treated animals; whereas, the numbers of both B and T cells (helper T and cytotoxic T, NKT cells) were decreased in the prednisolone-treated animals. Taken together, these results suggest that chloropheniramine administration enhances white blood cells in the peripheral blood, mostly due to increases of the B cells and monocytes, but no T cells and NK cells.

Toxicological identification of diphenhydramine (DPH) in suicide

Diphenhydramine (DPH), an H1-antihistamine, is identified during postmortem toxicological analyses on a relatively rare but still regular basis. This study examines suicidal intoxications with DPH by analyzing blood and gastric content concentration levels. Twenty cases of DPH intoxications within a 10-year period (2000-2010) were discovered by screening the autopsy records of the Institute of Legal Medicine and Forensic Sciences (ILMFS) in Berlin, Germany. In four cases, DPH levels were lower than 1 μg/mL and hence were not considered likely to be responsible for causing death. In 11 cases, DPH played a role in the fatal episode, and five of these cases were monointoxications. Considering that more than 8,000 autopsies were performed by the ILMFS within the time period under examination, there is only one monointoxication case every 2 years, which makes it a rare occurrence. In two of these intoxications, DPH was only measured in toxic but not "lethal" concentrations in blood, with a concentration of 5 μg/mL being generally used as the cut off between categories according to forensic literature. This raises the question as to whether a strict boundary for a "lethal" blood concentration, as suggested in some literature, can be set and applied in any of these cases. This study shows that an individual interpretation of each case is of utmost importance for correct classification. A thorough toxicological analysis of peripheral venous blood and gastric content, as well as a detailed work-up of the death circumstances, are the basis of an exact interpretation of intoxications with DPH.

Toxidromes

The critical care physician is often called to care for poisoned patients. This article reviews the general approach to the poisoned patient, specifically focusing on the utility of the toxidrome. A toxidrome is a constellation of findings, either from the physical examination or from ancillary testing, which may result from any poison. There are numerous toxidromes defined in the medical literature. This article focuses on the more common toxidromes described in clinical toxicology. Although these toxidromes can aid the clinician in narrowing the differential diagnosis, care must be exercised to realize the exceptions and limitations associated with each.

Update on the safety considerations in the management of insomnia with hypnotics: incorporating modified-release formulations into primary care

OBJECTIVE

From a safety perspective, several issues require assessment when a decision is made to prescribe a sleep medication, including next-day residual effects, the potential for abuse, tolerance, and dependence. This article aims to provide an update of the safety profile of agents commonly used in the management of insomnia, with an emphasis on newly approved hypnotics.

DATA SOURCES

Publications relevant to the subject of this review were identified by a PubMed search (conducted without date restrictions; search terms: insomnia WITH safety OR tolerability OR side effects OR tolerance OR dependence OR abuse OR residual effects AND benzodiazepines OR non-benzodiazepines OR zolpidem OR eszopiclone OR zaleplon OR ramelteon OR melatonin OR trazodone OR antihistamines OR alcohol OR alternative therapies), and additional articles (selected by the author on the basis of his experience) were included.

STUDY SELECTION AND DATA EXTRACTION

Publications relevant to the objective of this article were obtained, and the key safety data relating to adverse events, next-day residual effects, tolerance, and withdrawal were summarized.

DATA SYNTHESIS

The non-benzodiazepines (eszopiclone, zolpidem, zolpidem extended-release, and zaleplon), which have largely replaced the benzodiazepines for insomnia treatment, have a lower risk of tolerance, dependence, abuse, and residual effects compared with benzodiazepines. The modified-release formulation of zolpidem demonstrates a comparable safety profile to that of original zolpidem but has an additional sleep maintenance benefit. Ramelteon, a novel melatonin receptor agonist, is indicated for sleep-onset difficulties and is not scheduled. Over-the-counter agents, alternative therapies, and the prescription of off-label drugs, such as trazodone, have a lack of controlled clinical efficacy and safety studies in the treatment of insomnia and as a result should be used with caution.

CONCLUSIONS

Overall, published studies report that the safety of insomnia treatments has improved considerably over the past 10 years with the introduction of agents that provide improved safety, particularly with regard to next-day residual effects and abuse liability.

Efficacy of diphenhydramine in the prevention of vertigo and nausea at 7 T MRI

PURPOSE

In this study the potential of diphenhydramine in reducing respectively preventing vertigo and nausea induced by the ultra-high static magnetic field at 7 T was evaluated.

MATERIALS AND METHODS

In a prospective, double blinded, placebo controlled, cross-over randomized study the sensations of 34 volunteers before, during and after exposure to the static magnetic field with and without drug respectively placebo administration were quantified. Fast table motion was applied to increase the incidence of otherwise sparse reports of field related sensations.

RESULTS

The strength of vertigo can be reduced by the application of diphenhydramine.

CONCLUSION

Diphenhydramine, even at a low dose, reduces the strength of vertigo at ultra-high static magnetic fields, may be used preventively, and could pave the way to even higher field strength.

H1-antihistamine up-dosing in chronic spontaneous urticaria: patients' perspective of effectiveness and side effects--a retrospective survey study

BACKGROUND

The guidelines recommend that first line treatment of chronic spontaneous urticaria should be second generation non-sedating H(1)-antihistamines with a positive recommendation against the use of old sedating first generation antihistamines. If standard dosing is not effective, increasing the dosage up to four-fold is recommended. The objective of this study was to obtain the chronic spontaneous urticaria-patient perspective on the effectiveness and unwanted effects of H(1)-antihistamines in standard and higher doses.

METHODOLOGY/PRINCIPAL FINDINGS

This was a questionnaire based survey, initially completed by 368 individuals. 319 (248 female, 71 male, median age 42 years) had a physician-confirmed diagnosis of chronic spontaneous urticaria and were included in the results. Participants believed standard doses (manufacturers recommended dose) of second generation antihistamines to be significantly (P<0.005) more effective than first generation drugs. Furthermore, they believed that second generation drugs caused significantly (P<0.001) fewer unwanted effects and caused significantly (P<0.001) less sedation than first generation antihistamines. Three-quarters of the patients stated that they had up-dosed with antihistamines with 40%, 42% and 54% reporting significant added benefit from taking 2, 3 or 4 tablets daily respectively. The number of reports of unwanted effects and sedation following up-dosing were not significantly different from those reported for standard doses.

CONCLUSIONS

This survey supports the urticaria guidelines recommendations that the first line treatment for chronic spontaneous urticaria should be second generation rather than first generation H(1)-antihistamines and that, if standard dosing is not effective, the dosage should be increased up to four-fold.

Allergic rhinitis (AR) in geriatric patients

Allergic rhinitis (AR) can be defined as an inflammatory disease of the nose and the paranasal sinuses, characterized by a specific IgE-mediated hypersensitivity reaction. The aim of this study was to evaluate the correlation between the symptoms of AR and the prick test results in geriatric patients presenting with symptoms of AR by comparing these with those of a young control group. Thirty-two geriatric patients (Group 1) were analyzed retrospectively, and 37 patients (Group 2) were selected as the control group. Diagnosis of AR was made based upon the physical examination findings, nasal endoscopic examination findings and the skin prick test results. While the skin prick test positivity was 50% in Group 1, this rate was found as 75.7% in Group 2. The difference was found to be statistically significant (p=0.044). A statistically significant difference was found between the two groups in terms of susceptibility to mugwort pollen and fish (p=0.048, p=0.033). In conclusion, in geriatric patients presenting with AR symptoms, systemic treatment should not be initiated before performing skin prick test, due to the adverse effects of the drugs.

Rupatadine does not potentiate the CNS depressant effects of lorazepam: randomized, double-blind, crossover, repeated dose, placebo-controlled study

AIM

The main objective was to assess whether benzodiazepine intake when rupatadine plasma concentrations were at steady-state would increase the CNS depressant effects. Rupatadine is a new H(1)-antihistamine which also inhibits platelet activating factor (PAF) release and has been shown to be clinically effective at doses of 10 mg.

METHODS

Sixteen healthy young volunteers took part in a crossover, randomized, double-blind, placebo controlled trial comprising two experimental periods (repeated administration for 7 days of rupatadine 10 mg or placebo as single oral daily doses, separated by a washout of 14 days). On days 5 and 7, according to a fully balanced design, a single oral dose of lorazepam 2 mg or placebo was added. CNS effects were evaluated on these days by seven objective tests of psychomotor performance and eight subjective visual analogue scales (VAS) at pre-dose and several times after drug intake. Four treatment conditions were evaluated: placebo, rupatadine 10 mg, lorazepam 2 mg and rupatadine 10 mg + lorazepam 2 mg.

RESULTS

Significant CNS effects, either impairment of psychomotor performance or subjective sedation, were observed when lorazepam was administered, either alone or in combination with steady state concentrations of rupatadine. No significant differences were found between these two conditions. In addition, rupatadine was not different from placebo. All treatments were well tolerated.

CONCLUSION

Repeated doses of rupatadine (10 mg orally) did not enhance the CNS depressant effects of lorazepam (2 mg orally, single dose) either in objective psychomotor tasks or in subjective evaluations.

Risk of first-generation H(1)-antihistamines: a GA(2)LEN position paper

BACKGROUND

First-generation H(1)-antihistamines obtained without prescription are the most frequent form of self-medication for allergic diseases, coughs and colds and insomnia even though they have potentially dangerous unwanted effects which are not recognized by the general public.

AIMS

To increase consumer protection by bringing to the attention of regulatory authorities, physicians and the general public the potential dangers of the indiscriminate use first-generation H(1)-antihistamines purchased over-the counter in the absence of appropriate medical supervision.

METHODS

A GA(2)LEN (Global Allergy and Asthma European Network) task force assessed the unwanted side-effects and potential dangers of first-generation H1-antihistamines by reviewing the literature (Medline and Embase) and performing a media audit of US coverage from 1996 to 2008 of accidents and fatal adverse events in which these drugs were implicated.

RESULTS

First-generation H(1)-antihistamines, all of which are sedating, are generally regarded as safe by laypersons and healthcare professionals because of their long-standing use. However, they reduce rapid eye movement (REM)-sleep, impair learning and reduce work efficiency. They are implicated in civil aviation, motor vehicle and boating accidents, deaths as a result of accidental or intentional overdosing in infants and young children and suicide in teenagers and adults. Some exhibit cardiotoxicity in overdose.

CONCLUSIONS

This review raises the issue of better consumer protection by recommending that older first-generation H(1)-antihistamines should no longer be available over-the-counter as prescription- free drugs for self-medication of allergic and other diseases now that newer second- generation nonsedating H(1)-antihistamines with superior risk/benefit ratios are widely available at competitive prices.

Mapping pharmaceuticals in rat brain sections using MALDI imaging mass spectrometry

Matrix-assisted laser desorption/ionization-tandem mass spectrometric method (MALDI-MS/MS) has proven to be a reliable tool for direct measurement of the disposition of small molecules in animal tissue sections. As example, MALDI-MS/MS imaging system was employed for visualizing the spatial distribution of astemizole and its primary metabolite in rat brain tissues. Astemizole is a second-generation antihistamine, a block peripheral H1 receptor, which was introduced to provide comparable therapeutic benefit but was withdrawn in most countries due to toxicity risks. Astemizole was observed to be heterogeneously distributed to most parts of brain tissue slices including cortex, hippocampus, hypothalamic, thalamus, and ventricle regions while its major metabolite, desmethylastemizole, was only found around ventricle sites. We have shown that astemizole alone is likely to be responsible for the central nervous system (CNS) side effects when its exposures became elevated.

A proposal for a pharmacokinetic interaction significance classification system (PISCS) based on predicted drug exposure changes and its potential application to alert classifications in product labelling

BACKGROUND AND OBJECTIVE

Pharmacokinetic drug-drug interactions (DDIs) are one of the major causes of adverse events in pharmacotherapy, and systematic prediction of the clinical relevance of DDIs is an issue of significant clinical importance. In a previous study, total exposure changes of many substrate drugs of cytochrome P450 (CYP) 3A4 caused by coadministration of inhibitor drugs were successfully predicted by using in vivo information. In order to exploit these predictions in daily pharmacotherapy, the clinical significance of the pharmacokinetic changes needs to be carefully evaluated. The aim of the present study was to construct a pharmacokinetic interaction significance classification system (PISCS) in which the clinical significance of DDIs was considered with pharmacokinetic changes in a systematic manner. Furthermore, the classifications proposed by PISCS were compared in a detailed manner with current alert classifications in the product labelling or the summary of product characteristics used in Japan, the US and the UK.

METHODS

A matrix table was composed by stratifying two basic parameters of the prediction: the contribution ratio of CYP3A4 to the oral clearance of substrates (CR), and the inhibition ratio of inhibitors (IR). The total exposure increase was estimated for each cell in the table by associating CR and IR values, and the cells were categorized into nine zones according to the magnitude of the exposure increase. Then, correspondences between the DDI significance and the zones were determined for each drug group considering the observed exposure changes and the current classification in the product labelling. Substrate drugs of CYP3A4 selected from three therapeutic groups, i.e. HMG-CoA reductase inhibitors (statins), calcium-channel antagonists/blockers (CCBs) and benzodiazepines (BZPs), were analysed as representative examples. The product labelling descriptions of drugs in Japan, US and UK were obtained from the websites of each regulatory body.

RESULTS

Among 220 combinations of drugs investigated, estimated exposure changes were more than 5-fold for 41 combinations in which ten combinations were not alerted in the product labelling at least in one country; these involved buspirone, nisoldipine and felodipine as substrates, and ketoconazole, voriconazole, telithromycin, clarithromycin and nefazodone as inhibitors. For those drug combinations, the alert classifications were anticipated as potentially inappropriate. In the current product labelling, many inter-country differences were also noted. Considering the relationships between previously observed exposure changes and the current alert classifications, the boundaries between 'contraindication' and 'warning/caution' were determined as a 7-fold exposure increase for statins and CCBs, and as a 4-fold increase for BZPs. PISCS clearly discriminated these drug combinations in accordance with the determined boundaries. Classifications by PISCS were expected to be valid even for future drugs because the classifications were made by zones, not by designating individual drugs.

CONCLUSION

The present analysis suggested that many current alert classifications were potentially inappropriate especially for drug combinations where pharmacokinetics had not been evaluated. It is expected that PISCS would contribute to constructing a leak-less alerting system for a broad range of pharmacokinetic DDIs. Further validation of PISCS is required in clinical studies with key drug combinations, and its extension to other CYP and metabolizing enzymes remains to be achieved.

Prediction of pharmacokinetic drug-drug interaction caused by changes in cytochrome P450 activity using in vivo information

The aim of the present paper was to present an overview of the current status of the methods used to predict the magnitude of pharmacokinetic drug-drug interactions (DDIs) which are caused by apparent changes in cytochrome P450 (CYP) activity with an emphasis on a method using in vivo information. In addition, more than a hundred representative CYP substrates, inhibitor and inducer drugs involved in significant pharmacokinetic DDIs were selected from the literature and are listed. Although the magnitude of DDIs has been conventionally predicted based on in vitro experiments, their predictability is restricted occasionally due to several difficulties, including a precise determination of the unbound inhibitor concentrations at the enzyme site and a reliable in vitro measurement of the inhibition constant (K(i)). Alternatively, a simple method has been recently proposed for the prediction of the magnitude of DDIs based on information fully available from in vivo clinical studies. The new in vivo-based method would be applicable to the adjustment of dose regimens in actual pharmacotherapy situations although it requires a prior clinical study for the prediction. In this review, theoretical and quantitative relationships between the in vivo- and the in vitro-based prediction methods are considered. One of the interesting outcomes of the consideration is that the K(i)-normalized dose (dose/in vitro K(i)) of larger than approximately 20L (2-200L, when variability is considered) may be a pragmatic index which predicts significant in vivo DDIs. In the last part of the article, the relevance of the inclusion of the in vivo-based method into the process of new drug development is discussed for good prediction of in vivo DDIs.

MALDI–tandem mass spectrometry imaging of astemizole and its primary metabolite in rat brain sections

Background: Matrix-assisted laser desorption/ionization (MALDI)–tandem mass spectrometry (MS)/MS is a proven reliable tool for visualizing the spatial distribution of dosed drugs and their primary metabolites in animal tissue sections. Materials & methods: The rat brain tissue sections coated with dihydroxybenzoic acid as matrix, were analyzed by MALDI–MS/MS imaging experiments. The potential metabolites of astemizole in rat brain homogenate selected for MALDI–MS/MS imaging experiments were first identified by high-performance liquid chromatography coupled to an electrospray ionization source and a hybrid-quadrupole–linear-ion-trap mass spectrometer. Results: Astemizole was observed to be heterogeneously distributed to most parts of the brain tissue slices including the cortex, hippocampus, hypothalamic, thalamus and ventricle regions, while its major metabolite, desmethylastemizole, was only found around ventricle sites. Conclusion: The results indicated that the dosed compound alone might be responsible for the CNS side-effects when drug exposures became elevated.

Cocaine-like neurochemical effects of antihistaminic medications

The pattern of activation of dopamine (DA) neurotransmission in the nucleus accumbens (NAc) of rats produced by H(1) histamine antagonists which have behavioral effects like those of psychostimulant drugs was examined. Diphenhydramine and (+)-chlorpheniramine were compared with triprolidine, a potent and selective H(1) antagonist and (-)-chlorpheniramine which is less active than its enantiomer at H(1) receptors. Affinities of the drugs to DA, serotonin, and norepinephrine transporters at H(1) receptors and potencies for DA uptake inhibition in striatal synaptosomes were determined to assess mechanisms by which the compounds increased DA levels. Intravenous diphenhydramine (1.0-3.0 mg/kg) (+)- and (-)-chlorpheniramine (1.0-5.6 mg/kg) but not triprolidine (1.0-3.0 mg/kg) elicited a cocaine-like pattern of stimulation of DA transmission with larger effects in the NAc shell than core. The absence of stereospecific effects with chlorpheniramine enantiomers along with the lack of an effect with triprolidine suggest that the effects on DA transmission were not related to H(1) receptor antagonism. Although in vivo potencies were not directly related to DA transporter affinities, it is hypothesized that actions at that site modulated by other actions, possibly those at the serotonin transporter, are primarily responsible for the neurochemical actions of the drugs on DA neurotransmission and might underlie the occasional misuse of these medications.

Keys to successful management of patients with allergic rhinitis: focus on patient confidence, compliance, and satisfaction

OBJECTIVE

The American Academy of Otolaryngic Allergy (AAOA) convened an expert, multidisciplinary Working Group on Allergic Rhinitis to discuss patients' self-treatment behaviors and how health care providers approach and treat the condition. PROCEDURES AND DATA SOURCES: Co-moderators, who were chosen by the AAOA Board of Directors, were responsible for initial agenda development and selection of presenters and participants, based on their expertise in diagnosis and treatment of allergic rhinitis. Each presenter performed a literature search from which a presentation was developed, portions of which were utilized in developing this review article.

SUMMARY OF FINDINGS

Allergic rhinitis is a common chronic condition that has a significant negative impact on general health, co-morbid illnesses, productivity, and quality of life. Treatment of allergic rhinitis includes avoidance of allergens, immunotherapy, and/or pharmacotherapy (ie, antihistamines, decongestants, corticosteroids, mast cell stabilizers, anti-leukotriene agents, anticholinergics). Despite abundant treatment options, 60% of all allergic rhinitis patients in an Asthma and Allergy Foundation of America survey responded that they are "very interested" in finding a new medication and 25% are "constantly" trying different medications to find one that "works." Those who were dissatisfied also said their health care provider does not understand their allergy treatment needs and does not take their allergy symptoms seriously. Dissatisfaction leads to decreased compliance and an increased reliance on multiple agents and over-the-counter products. Furthermore, a lack of effective communication between health care provider and patient leads to poor disease control, noncompliance, and unhappiness in a significant portion of patients.

CONCLUSIONS

Health care providers must gain a greater understanding of patient expectations to increase medication compliance and patient satisfaction and confidence.

Lack of effects between rupatadine 10 mg and placebo on actual driving performance of healthy volunteers

INTRODUCTION

Rupatadine fumarate is a potent, selective, histamine H(1)-receptor antagonist and PAF inhibitor with demonstrated efficacy for the relief of allergic rhinitis. Rupatadine does not easily cross the blood-brain barrier and is believed to be non-sedating at therapeutic doses. Consequently, rupatadine should show no impairment on car driving.

OBJECTIVE

This study compared the acute effects of rupatadine, relative to placebo and hydroxyzine (as an active control), on healthy subjects' driving performance.

METHODS

Twenty subjects received a single dose of rupatadine 10 mg, hydroxyzine 50 mg, or placebo in each period of this randomized, double-blind, three-way crossover study. Two hours postdosing, subjects operated a specially instrumented vehicle in tests designed to measure their driving ability. Before and after the driving tests ratings of sedation were recorded.

RESULTS

There was no significant difference between rupatadine and placebo in the primary outcome variable: standard deviation of lateral position (SDLP); however, hydroxyzine treatment significantly increased SDLP (p < 0.001 for both comparisons). Objective (Stanford sleepiness scale) and subjective sedation ratings (Visual Analogue Scales) showed similar results: subjects reported negative effects after hydroxyzine but not after rupatadine.

CONCLUSION

Rupatadine 10 mg is not sedating and does not impair driving performance.

Effects of desloratadine and alcohol coadministration on psychomotor performance

OBJECTIVE

This study was set up to evaluate the effects of desloratadine 7.5 mg daily, with and without alcohol, on sedation and psychomotor performance.

RESEARCH METHODS

In a double-blind, placebo-controlled, four-way crossover trial, 25 adult patients were randomized to desloratadine 7.5 mg, desloratadine 7.5 mg plus alcohol, placebo, or placebo plus alcohol. Alcohol was weight adjusted to an average blood alcohol concentration of 0.1%. Assessments included the modified Romberg test, Stanford Sleepiness Scale, Digit Symbol Substitution Test, Serial Add Subtract Reaction Time Test, and the Psychomotor Vigilance Test. The primary variable was the mean score of each of the five tests averaged over the treatment period, expressed as the mean percent change from baseline.

RESULTS

Across these assessments, differences between desloratadine alone or with alcohol versus placebo alone or without alcohol, were not significant, whereas most differences between desloratadine and placebo alone versus desloratadine and placebo with alcohol were significant (p < 0.01). Thus, with or without alcohol, desloratadine 7.5 mg does not increase sedation or impair psychomotor performance. Most adverse events (AEs) were mild-to-moderate in severity, with the most frequently reported individual AEs being headache, fatigue, nausea, vomiting, and dry mouth. The study does have potential limitations. The measures used are restricted to a particular profile of the known effects of alcohol only, and the relatively high doses of alcohol used alone demonstrate effects on psychomotor function and attention.

CONCLUSIONS

A single dose of desloratadine does not potentiate alcohol-mediated CNS impairment. Desloratadine alone or in combination with alcohol was safe and well tolerated.

Pharmacokinetics and Safety of Ebastine in Healthy Subjects and Patients with Renal Impairment

OBJECTIVE

To assess the differences in the pharmacokinetics and cardiac safety of ebastine and its active metabolite, carebastine, in patients with normal and impaired renal function.

METHODS

Twenty-four patients with varying degrees of renal impairment (mild, moderate or severe: n = 8 per group) and 12 healthy subjects participated in an open-label, parallel-group, multicentre study. Ebastine 20mg was administered orally once daily for 5 days. Plasma concentrations of ebastine and carebastine were determined for 24 hours on day 1 and for 72 hours on day 5 by using a validated sensitive liquid chromatography-tandem mass spectrometry assay with a minimum quantifiable limit of 0.05 ng/mL for ebastine and 1.00 ng/mL for carebastine. Renal function was assessed by measuring 24-hour creatinine clearance (CL(CR)) at baseline. Cardiac and general safety parameters were also monitored.

RESULTS

The pharmacokinetics of ebastine were not modified by renal impairment. No correlation between ebastine pharmacokinetics and renal function, as expressed by CL(CR) assessed 2 days prior to dosing, was observed. Comparison of the plasma exposure and the elimination half-life of ebastine and carebastine between groups showed no significant differences. Therefore, no apparent accumulation of ebastine and carebastine occurred, and steady-state concentrations of ebastine and carebastine were predictable from single-dose pharmacokinetics for both healthy subjects and patients with renal impairment, even though the variability between the groups was large. In addition, no differences were observed in the safety of ebastine between patients with renal impairment and healthy subjects when assessing adverse events, vital signs, laboratory parameters or ECGs.

CONCLUSION

Ebastine was generally well tolerated in subjects with impaired renal function. No clinically important pharmacokinetic or safety differences were observed between patients with renal impairment and healthy subjects with normal renal function.

General Framework for the Quantitative Prediction of CYP3A4-Mediated Oral Drug Interactions Based on the AUC Increase by Coadministration of??Standard Drugs

BACKGROUND

Cytochrome P450 (CYP) 3A4 is the most prevalent metabolising enzyme in the human liver and is also a target for various drug interactions of significant clinical concern. Even though there are numerous reports regarding drug interactions involving CYP3A4, it is far from easy to estimate all potential interactions, since too many drugs are metabolised by CYP3A4. For this reason, a comprehensive framework for the prediction of CYP3A4-mediated drug interactions would be of considerable clinical importance.

OBJECTIVE

The objective of this study was to provide a robust and practical method for the prediction of drug interactions mediated by CYP3A4 using minimal in vivo information from drug-interaction studies, which are often carried out early in the course of drug development.

DATA SOURCES

The analysis was based on 113 drug-interaction studies reported in 78 published articles over the period 1983-2006. The articles were used if they contained sufficient information about drug interactions. Information on drug names, doses and the magnitude of the increase in the area under the concentration-time curve (AUC) were collected.

METHODS

The ratio of the contribution of CYP3A4 to oral clearance (CR(CYP)(3A4)) was calculated for 14 substrates (midazolam, alprazolam, buspirone, cerivastatin, atorvastatin, ciclosporin, felodipine, lovastatin, nifedipine, nisoldipine, simvastatin, triazolam, zolpidem and telithromycin) based on AUC increases observed in interaction studies with itraconazole or ketoconazole. Similarly, the time-averaged apparent inhibition ratio of CYP3A4 (IR(CYP)(3A4)) was calculated for 18 inhibitors (ketoconazole, voriconazole, itraconazole, telithromycin, clarithromycin, saquinavir, nefazodone, erythromycin, diltiazem, fluconazole, verapamil, cimetidine, ranitidine, roxithromycin, fluvoxamine, azithromycin, gatifloxacin and fluoxetine) primarily based on AUC increases observed in drug-interaction studies with midazolam. The increases in the AUC of a substrate associated with coadministration of an inhibitor were estimated using the equation 1/(1 - CR(CYP)(3A4) x IR(CYP)(3A4)), based on pharmacokinetic considerations.

RESULTS

The proposed method enabled predictions of the AUC increase by interactions with any combination of these substrates and inhibitors (total 251 matches). In order to validate the reliability of the method, the AUC increases in 60 additional studies were analysed. The method successfully predicted AUC increases within 67-150% of the observed increase for 50 studies (83%) and within 50-200% for 57 studies (95%). Midazolam is the most reliable standard substrate for evaluation of the in vivo inhibition of CYP3A4. The present analysis suggests that simvastatin, lovastatin and buspirone can be used as alternatives. To evaluate the in vivo contribution of CYP3A4, ketoconazole or itraconazole is the selective inhibitor of choice.

CONCLUSION

This method is applicable to (i) prioritize clinical trials for investigating drug interactions during the course of drug development and (ii) predict the clinical significance of unknown drug interactions. If a drug-interaction study is carefully designed using appropriate standard drugs, significant interactions involving CYP3A4 will not be missed. In addition, the extent of CYP3A4-mediated interactions between many other drugs can be predicted using the current method.

Simultaneous determination of ten antihistamine drugs in human plasma using pipette tip solid-phase extraction and gas chromatography/mass spectrometry

Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18- bonded monolithic silica gel was fixed. Human plasma (0.1 mL) containing the ten antihistamines was mixed with 0.4 mL of distilled water and 25 microL of a 1 M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30 m x 0.32 mm i.d., film thickness 0.25 microm). The recoveries of the ten antihistamines spiked into plasma were 73.8-105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02-5.0 ng/0.1 mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented.

Cognitive Effects of Allergic Rhinitis and its Treatment

Allergic rhinitis (AR) can, by itself, introduce significant sedation and impairment of cognition and performance. AR can also impede restorative sleep, resulting in increased fatigue and decreased daytime performance. It is not clear whether improved alertness resulting from blocking histamine production offsets the sedating effects of antihistamines or whether the effects of disease and treatment combine to create even greater sedation. This article reviews and integrates this literature, offers conclusions based on the collective evidence, and suggests guidelines for future research.

Similar rapid onset of action and magnitude of effect of fexofenadine and cetirizine as assessed by inhibition of histamine-induced wheal-and-flare reaction

BACKGROUND

Histamine-induced wheal-and-flare studies are useful, objective tests for determining differences in the peripheral H1-receptor blockade activities of antihistamines.

OBJECTIVE

To evaluate the time of occurrence of 95% inhibition of histamine-induced wheal and flare after administration of fexofenadine hydrochloride, 180 mg, or cetirizine, 10 mg.

METHODS

Forty-two volunteers (aged 18-60 years) were included in a randomized, double-blind, crossover study. Skin prick tests were undertaken using histamine (100 mg/mL) before treatment and 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 hours after treatment. Wheal and flare areas were evaluated, and the time to occurrence of 95% inhibition and the frequency of subjects exhibiting 95% inhibition before median time to 95% inhibition were calculated.

RESULTS

Mean +/- SD time to 95% wheal inhibition was 2.46 +/- 0.71 hours with fexofenadine and 2.55 +/- 0.57 hours with cetirizine. The estimated mean difference between fexofenadine and cetirizine (-7 minutes in favor of fexofenadine; 2-sided 95% confidence interval, -21 to +7 minutes) was not statistically significant (P = .34). For wheal, 29% of subjects receiving fexofenadine and 24% receiving cetirizine achieved 95% inhibition before the median time of inhibition (2.5 hours). An exact permutation test yielded a P = .37. For flare, 26% of subjects receiving fexofenadine and 10% receiving cetirizine achieved 95% inhibition before the median time of inhibition (3 hours; P = .12 by exact permutation test).

CONCLUSIONS

Fexofenadine and cetirizine have comparable onset of action times and similar frequencies of inhibition, as evaluated by the occurrence of 95% inhibition of histamine-induced wheal and flare.

Cetirizine: a review of its use in allergic disorders

Cetirizine is a selective, second-generation histamine H1 receptor antagonist, with a rapid onset, a long duration of activity and low potential for interaction with drugs metabolised by the hepatic cytochrome P450 system. Cetirizine was generally more effective than other H1 receptor antagonists at inhibiting histamine-induced wheal and flare responses. Cetirizine is an effective and well tolerated agent for the treatment of symptoms of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR) and chronic idiopathic urticaria (CIU) in adult, adolescent and paediatric patients. In adults with these allergic disorders, cetirizine was as effective as conventional dosages of ebastine (SAR, PAR, CIU), fexofenadine (SAR), loratadine (SAR, CIU) or mizolastine (SAR). This agent was significantly more effective, and with a more rapid onset of action, than loratadine in 2-day studies in environmental exposure units (SAR). In paediatric patients, cetirizine was as at least as effective as chlorphenamine (chlorpheniramine) [SAR], loratadine (SAR, PAR) and oxatomide (CIU) in the short term, and more effective than oxatomide and ketotifen (PAR) in the long term. Cetirizine was effective in reducing symptoms of allergic asthma in adults and reduced the relative risk of developing asthma in infants with atopic dermatitis sensitised to grass pollen or house dust mite allergens. It had a corticosteroid-sparing effect in infants with severe atopic dermatitis and was effective in ameliorating reactions to mosquito bites in adults. Cetirizine was well tolerated in adults, adolescents and paediatric patients with allergic disorders. In adult, adolescent and paediatric patients aged 2-11 years, the incidence of somnolence with cetirizine was dose related and was generally similar to that with other second-generation H1 receptor antagonists. Although, its sedative effect was greater than that of fexofenadine in some clinical trials and that of loratadine or fexofenadine in a postmarketing surveillance study. In infants aged 6-24 months, the tolerability profile of cetirizine was similar to that of placebo. Cetirizine did not have any adverse effects on cognitive function in adults, or cognitive function, behaviour or achievement of psychomotor milestones in paediatric patients. Cetirizine was not associated with cardiotoxicity.

CONCLUSION

Cetirizine is well established in the treatment of symptoms of SAR, PAR or CIU. It demonstrated a corticosteroid-sparing effect and reduced the relative risk of developing asthma in sensitised infants with atopic dermatitis. Cetirizine was effective in the treatment of allergic cough and mosquito bites; however, its precise role in these indications has yet to be clearly established. On the basis of its favourable efficacy and tolerability profile and rapid onset of action, cetirizine provides an important option for the treatment of a wide range of allergic disorders.

The economic impact of payer policies after the Rx-to-OTC switch of second-generation antihistamines

OBJECTIVE

As a result of the over-the-counter (OTC) introduction of loratadine, health plans have been struggling to determine the best policy to incorporate this change within their existing drug benefit structure for second-generation antihistamines (SGA). The objective of this study was to examine the economic impact of payer policies in response to the Rx-to-OTC switch of loratadine.

STUDY DESIGN

Decision analysis was used to model the budgetary impact and cost-effectiveness of four policies for SGA benefits for the managed care organization (MCO), employer, and Medicaid perspectives separately.

PATIENTS AND METHODS

Outcomes included direct medical costs and lost productivity (employers only), discounted, quality-adjusted life-years (QALYs) saved because of amelioration of allergic rhinitis symptoms and avoidance of unintentional injuries associated with the use of first-generation antihistamines (FGA). Bayesian probabilistic sensitivity analysis was conducted using second-order Monte Carlo simulation.

RESULTS

Providing limited OTC and second-tier prescription benefits would cost approximately 0.13 dollars and 0.30 dollars compared to third-tier prescription benefits for employers and MCOs, respectively, and would save Medicaid 0.02 dollars per member per month (PMPM). Providing limited coverage for OTC loratadine while retaining second-tier prescription benefits for SGA was the optimal policy for a willingness to pay below 26,200 dollars per QALY for all payers.

CONCLUSIONS

Offering second-tier prescription and limited OTC benefits provides greater effectiveness and is not significantly more expensive PMPM than discontinuation. Some of the drug savings from limiting coverage of prescription SGA may be attenuated by the cost of lost productivity and direct medical expenditures due to unintentional injuries associated with increased FGA use in addition to the increased cost of therapeutic substitutes.

A randomized evaluation of the effects of six antipsychotic agents on QTc, in the absence and presence of metabolic inhibition

Many drugs have been associated with QTc prolongation and, in some cases, this is augmented by concomitant administration with metabolic inhibitors. The effects of 6 antipsychotics on the QTc interval at and around the time of estimated peak plasma/serum concentrations in the absence and presence of metabolic inhibition were characterized in a prospective, randomized study in which patients with psychotic disorders reached steady-state on either haloperidol 15 mg/d (n = 27), thioridazine 300 mg/d (n = 30), ziprasidone 160 mg/d (n = 31), quetiapine 750 mg/d (n = 27), olanzapine 20 mg/d (n = 24), or risperidone 6-8 mg/d increased to 16 mg/d (n = 25/20). Electrocardiograms (ECGs) were done at estimated Cmax at steady-state on both antipsychotic monotherapy and after concomitant administration of appropriate cytochrome P-450 (CYP450) inhibitor(s). Mean QTc intervals did not exceed 500 milliseconds in any patient taking any of the antipsychotics studied, in the absence or presence of metabolic inhibition. The mean QTc interval change was greatest in the thioridazine group, both in the presence and absence of metabolic inhibition. The presence of metabolic inhibition did not significantly augment QTc prolongation associated with any agent. Each of the antipsychotics studied was associated with measurable QTc prolongation at steady-state peak plasma concentrations, which was not augmented by metabolic inhibition. The theoretical risk of cardiotoxicity associated with QTc prolongation should be balanced against the substantial clinical benefits associated with atypical antipsychotics and the likelihood of other toxicities.

Cost-benefit analysis of first-generation antihistamines in the treatment of allergic rhinitis

BACKGROUND

The majority of individuals with allergic rhinitis in the US take first-generation antihistamines (FGAs). Although FGAs have been proven effective in alleviating allergic rhinitis symptoms, they have been associated with an increased risk of motor vehicle, aviation and occupational injuries and deaths, reduced productivity and impaired learning.

OBJECTIVE

The objective of this analysis was to quantify the total costs and benefits of FGA use in the US from the societal perspective.

METHODS

We used a decision-analytic model to quantify the annual societal costs and benefits of treatment with FGAs compared with the hypothetical alternative of no treatment for the population of individuals with allergic rhinitis and taking FGAs in the US in 2001. The benefit associated with FGA use was estimated using the willingness-to-pay framework and projected to the US population using published estimates of the prevalence of allergic rhinitis. The costs of FGA-associated sedation included lost productivity and the direct and indirect cost of unintentional injuries (including motor vehicle, occupational, public and home injuries and fatalities). The incidence of injuries and fatalities associated with FGA use was estimated using the risk of injury attributable to the sedentary effects of FGAs in the allergic rhinitis population. To evaluate uncertainty in the model assumptions, a probabilistic sensitivity analysis was conducted using Bayesian second-order Monte Carlo simulation. Costs and benefits are expressed in 2001 US dollars, using a 3% discount rate.

RESULTS

Based on current utilisation, the total societal benefit (95% credible interval) associated with the use of FGAs for the treatment of allergic rhinitis was US 7.7 billion dollars (US 1.3 billion dollars to US 21 billion dollars). The societal cost of purchasing FGAs was only US 697 million dollars. However, the societal cost of FGA-associated sedation was US 11.3 billion dollars (US 2.4 billion dollars to US 50.8 billion dollars). The annual societal net benefit of FGA use for the treatment of allergic rhinitis in the US was -US4.2 billion dollars (-US 36 billion dollars to +US 0.296 billion dollars). The net benefit was negative in 97% of the 10,000 Monte Carlo simulations.

CONCLUSIONS

The societal benefits of FGA use in alleviating the symptoms of allergic rhinitis are significant. However, based on the assumptions, probability distributions and parameter estimate ranges used in the current model, it is very likely that the costs associated with sedation exceed the benefits of FGA use in the US. The cost of FGA-associated sedation is comparable to estimates of the cost of all medical care expenditures on respiratory conditions in the US (US 12.1 billion dollars to US 31.3 billion dollars) [1996 values] and provides compelling evidence of the economic burden of sedation associated with FGA use.