Adverse drug reactions: back to the future

Advances in the Pathomechanisms of Delayed Drug Hypersensitivity

Delayed drug hypersensitivity continues to contribute to major clinical problems worldwide. The clinical presentations of delayed drug hypersensitivity are diverse, ranging from mild skin rashes to life-threatening systemic reactions. The pathomechanism of delayed drug hypersensitivity involves human leukocyte antigens (HLA) presentation of drugs/metabolites to T cell receptors (TCR), resulting in T-cell activation. The pathogenesis of delayed drug hypersensitivity also has reactivation of the virus, and activation of many immune mediators. In this review, we discuss the immune pathogenesis, molecular interactions of HLA/drugs/TCR, and downstream signaling of cytotoxic proteins/cytokines/chemokines, as well as disease prevention and management for delayed drug hypersensitivity.

Maternal paracetamol intake and fetal ductus arteriosus constriction/closure: comprehensive signal evaluation using the Austin Bradford Hill criteria

PURPOSE

Acetaminophen (APAP) is available over-the-counter and widely regarded as safe for use in pregnancy. APAP has been used to close a persistently patent ductus arteriosus. Fetal constriction/closure of the ductus arteriosus (FCCDA), of public health interest given the drug's widespread use during pregnancy, is being monitored globally, including by the European Medicines Agency Pharmacovigilance Risk Assessment Committee. Our objective was to share a comprehensive signal evaluation of FCCDA with in utero APAP exposure to determine if the totality of evidence is sufficiently more consistent with one of the following two possibilities: (1) APAP never contributes to FCCDA (null hypothesis or H_O) versus (2) APAP may in some cases be at least a contributory cause of in utero DA narrowing (alternative hypothesis or H_A) to justify risk communication.

METHODS

To assess the relative support for H_O versus H_A, we synthesize and interpret within an Austin Bradford Hill criteria framework a comprehensive, cross-disciplinary set of published information and de novo analysis, including toxicology, epidemiology, clinical pharmacology, and clinical and quantitative pharmacovigilance analysis of spontaneous reports.

RESULTS

While residual uncertainty remains, the totality of information is more compatible with H_A than H₀, to the extent that it is reasonably possible that APAP may sometimes be at least a contributory cause of FCCDA.

CONCLUSION

It is reasonably possible that APAP may sometimes be at least a contributory cause of FCCDA, and this should therefore be communicated to stakeholders.

TRIAL REGISTRATION

CLINICALTRIALS.

GOV REGISTRATION

NOT APPLICABLE.

Multi-Ethnic Analysis of Cardiac Pharmacogenetic Markers of Cytochrome P450 and Membrane Transporters Genes in the Russian Population

Aim. To summarize Russian studies using pharmacogenetic testing as applied to cardiology.Material and methods. The authors conducted an online search for articles in December 2018 using the following databases: PubMed, Google Scholar, eLIBRARY. The search was carried out by keywords: "Russia", "Russian", "cardiology" together with the terms associated with the polymorphic marker, including: «P450», «CYP2C19», «CYP2D6», «CYP2B1», «CYP2B6», «CYP2Е1», «CYP2C8», «CYP2C9», «CYP3A4», «CYP3A5», «CYP1A1», «CYP1A2», «CYP4F2», «CYP4F1», «ABCB1», «SLCO1B1», «VKORC1», «GGCX», «SULT1A1», «CULT1», «CES1», «gene», «genes», «pharmacogenetics», «pharmacogenomics», «ethnic group».Results. Generalization of information allowed to identify obscure genes that need to be investigated in pharmacogenetic studies. This information can be used for the development of dosing algorithms and the priority choice of drugs, considering the results of pharmacogenetic testing and planning future research.Conclusion. The results of the literature review indicate the importance of studying the most clinically valid and clinically useful pharmacogenetic markers (CYP2C19, CYP2C9, VKORC1, SLCO1B1) among various ethnic groups in the Russian Federation. With the accumulation of evidence of clinical validity and clinical utility of other pharmacogenetic markers (CES1, CYP2D6*4, etc.), the problem of interethnic differences in the carriage of clinically significant polymorphisms of these genes identified in previous studies in the Russian Federation increasingly requires attention. The most promising for the introduction into the clinical practice in the Russian Federation in the near future are polymorphic markers of the CYP2C19, CYP2C9, VKORC1 and SLCO1B1 genes.

The observed effect of adverse drug reactions on the length of hospital stay among medical inpatients in a Nigerian University Teaching Hospital

Background:

The potential impact of an adverse drug reaction (ADR) is multidimensional, and includes prolonged length of hospitalization which significantly increased morbidity, mortality, and economic burden with additional intense medical care.

Aim:

This study was designed to characterize and evaluate the potential effect of ADRs on the length of hospital stay among adult medical inpatients in an academic teaching hospital in a large West African nation. The overarching goal of the study is to highlight approaches toward mitigating the sequelae of ADRs in this setting, and improving their recognition and timely optimal management.

Methods:

The patients admitted into the adult medical wards of a Nigerian University Teaching Hospital over a 9-month period from December 2013 to August 2014 were prospectively recruited for the study and followed up till discharge.

Results:

A total of 507 patients were evaluated during the study, out of which 269 (53.1%) of them were males and 238 (46.9%) were females. The mean age of the study population was 48.9 ± 17.8 years (median of 46 years). In this study, the mean duration of hospital stay for all patients was 11.9 ± 11.3 days (median of 9 days). Females had a mean duration stay of 12.9 ± 12.3 days (median of 10 days) and stayed significantly longer than males who stayed a mean duration of 10.9 ± 10.2 days with a median of 7 days ( t = −1.985, df = 505, p = 0.048). Furthermore, patients admitted solely because of ADRs (ADR-out) had a significantly shorter duration of stay with a mean duration stay of 6.1 ± 3.7 days (median duration stay of 7 days) when compared to those without ADRs whose mean duration of stay was 11.6 ± 11.0 days (median duration stay of 8 days), and this was found to be statistically significant ( t = 2.110, df = 472, p = 0.035). Those patients who developed ADRs during admission (ADR-in) had a mean duration of stay of 18.3 ± 14.8 (median of 15 days). This was significantly longer than the duration of stay for patients without ADRs ( t = −3.398, df = 487, p = 0.001) and also significantly longer than the duration for those who were admitted solely because of ADRs ( t =3.432, df = 49, p = 0.001).

Conclusion:

In this study, ADRs were associated with a significantly prolonged length of hospital stay for adult medical inpatients in this Nigerian University Teaching Hospital.

Clinical factors predicting drug-induced liver injury due to flucloxacillin

Objectives

Drug-induced liver injury (DILI) is a serious adverse reaction due to flucloxacillin. The pathogenesis is not fully understood. Female sex, age over 60 years, and a longer treatment duration have been suggested to be predisposing factors. Carriers of HLA-B*57:01 have an 80-fold increased risk, but due to the rarity of the reaction, testing of all patients is not cost-effective. We aimed to validate and detect clinical risk factors for flucloxacillin DILI.

Methods

Clinical characteristics of flucloxacillin-treated patients with (n=50) and without DILI (n=2,330) were compared in a retrospective case control study. Cases were recruited from the Swedish database of spontaneously reported adverse drug reactions. Treated controls were selected from the Swedish Twin Registry. Statistical comparisons were made using chi-squared test and logistic regression. The significance threshold was set to P<0.00357 to correct for multiple comparisons. Reliable variables were tested in a multiple regression model.

Results

DILI was associated with female sex, OR 2.79, 95% CI 1.50-5.17, P=0.0011, and with a history of kidney stones, OR 5.51, 95% CI 2.21-13.72, P=0.0003. Cases were younger than controls, OR per increase in years 0.91, 95% CI 0.88-0.94, P<0.0001, probably due to selection bias. No difference in treatment duration was detected, OR 1.03, 95% CI 0.98-1.08, P=0.1790.

Conclusion

We established female sex as a risk factor for flucloxacillin-induced DILI, and a history of kidney stones was identified as a potential risk factor. Clinical risk factors for flucloxacillin-induced DILI could be used to indicate whom to test for HLA-B*57:01 before treatment.

Drug allergy

Drug allergy encompasses a spectrum of immunologically-mediated hypersensitivity reactions with varying mechanisms and clinical presentations. This type of adverse drug reaction not only affects patient quality of life, but may also lead to delayed treatment, unnecessary investigations, and even mortality. Given the myriad of symptoms associated with the condition, diagnosis is often challenging. Therefore, referral to an allergist experienced in the identification, diagnosis and management of drug allergy is recommended if a drug-induced allergic reaction is suspected. Diagnosis relies on a careful history and physical examination and, in some instances, skin testing and graded challenges. Induction of drug tolerance procedures may also be required. The most effective strategy for the management of drug allergy is avoidance or discontinuation of the offending drug. When available, alternative medications with unrelated chemical structures should be substituted. Cross-reactivity among drugs should be taken into consideration when choosing alternative agents. Additional therapy for drug hypersensitivity reactions is largely supportive and may include topical corticosteroids, oral antihistamines and, in severe cases, systemic corticosteroids. In the event of anaphylaxis, the treatment of choice is injectable epinephrine. If a particular drug to which the patient is allergic is indicated and there is no suitable alternative, induction of drug tolerance procedures may be considered to induce temporary tolerance to the drug. This article provides a background on drug allergy and strategies for the diagnosis and management of some of the most common drug-induced allergic reactions, such as penicillin, sulfonamides, cephalosporins, radiocontrast media, local anesthetics, general anesthetics, acetylsalicylic acid and non-steroidal anti-inflammatory drugs, and therapeutic monoclonal antibodies.

The 10-D assessment and evidence-based medicine tool for authors and peer reviewers in clinical pharmacology

Background: Peer reviewers and authors of clinical pharmacology manuscripts need to meet the standards for Evidence-Based Medicine (EBM) and Good Publication Practices (GPP), and editors of clinical pharmacology journals have to maintain an overview of the peer review process. Methods and results: The peer review process can be monitored and facilitated using the 10-D assessment, which comprises peer review criteria to determine if: 1. design of the study, 2. diagnoses employed, 3. drug molecules involved, 4. dosages applied, 5. data collected, 6. discussion of the findings, 7. deductions made, 8. documentation, 9. declarations, and 10. dHS (drug hypersensitivity syndrome) risk assessment is in accord with the objectives of the study and meet the requirements of EBM and GPP. Conclusions: The 10-D assessment tool, although easy to apply, requires a high level of clinical pharmacology expertise, especially in the fields of drug disposition, pharmacokinetics, and drug action. Its application will facilitate the peer review of clinical research and clinical trial reports and thus promote safety in drug development and pharmacotherapy and meet the needs of Good Publication Practices.

The effects of distraction on symptoms during drug provocation test

Background

Some patients may have psychosomatic complaints due to their previous experiences during the drug hypersensitivity reaction. Worry about being hurt due to an administered drug is termed nocebo effect, which is the opposite of the placebo effect. In our study, we investigated the effect of distraction on symptoms during drug provocation test.

Methods

Our study included 112 patients who underwent DPTs for alternative purposes in our clinic. Previous hypersensitivity reactions of all the patients had objective signs. Patients were divided into two groups for the DPT. Sixty-three patients were kept busy during the test, performing tasks such as filling questionnaires, arranging files in alphabetical and numerical order, and doing archiving (Group 1). Forty-nine patients did not perform any tasks during the test (Group 2). Reactions that occurred during the test were recorded.

Results

During the DPT, 5 patients in Group 1 (5/63, 7.9%) and 17 patients in Group 2 (17/49, 34.7%), i.e. a total of 22 patients (22/112, 19.6%), had a reaction. There was a statistically significant difference between Group 1 and Group 2 according to the frequency of the reaction development.

Conclusions

Patient psychosomatic complaints during DPTs are proportional to their association with previous allergic reactions. In order to prevent such reactions, it may be beneficial to keep the patients busy with an activity in order to distract them during the test.

Non-psychotropic medication and risk of suicide or attempted suicide: a systematic review

OBJECTIVES

To establish which non-psychotropic medications have been assessed in relation to risk of suicide or attempted suicide in observational studies, document reported associations and consider study strengths and limitations.

DESIGN

Systematic review.

METHODS

Four databases (Embase, Medline, PsycINFO and International Pharmaceutical Abstracts) were searched from 1990 to June 2014, and reference lists of included articles were hand-searched. Case-control, cohort and case only studies which reported suicide or attempted suicide in association with any non-psychotropic medication were included.

OUTCOME MEASURES

The outcomes eligible for inclusion were suicide and attempted suicide, as defined by the authors of the included study.

RESULTS

Of 11,792 retrieved articles, 19 were eligible for inclusion. Five studies considered cardiovascular medication and antiepileptics; two considered leukotriene receptor antagonists, isotretinoin and corticosteroids; one assessed antibiotics and another assessed varenicline. An additional study compared multiple medications prescribed to suicide cases versus controls. There was marked heterogeneity in study design, outcome and exposure classification, and control for confounding factors; particularly comorbid mental and physical illness. No increased risk was associated with cardiovascular medications, but associations with other medications remained inconclusive and meta-analysis was inappropriate due to study heterogeneity.

CONCLUSIONS

Whether non-psychotropic medications are associated with increased risk of suicide or attempted suicide remains largely unknown. Robust identification of suicide outcomes and control of comorbidities could improve quantification of risk associated with non-psychotropic medication, beyond that conferred by underlying physical and mental illnesses.

[DRESS syndrome associated with carbamazepine]

BACKGROUND

DRESS syndrome (Drug Rash with Eosinophilia and Systemic Symptoms) is a serious adverse reaction to medication. It is usually defined by the triad of fever, rash and symptomatic or asymptomatic involvement of internal organs. Diagnostic criteria are suspected drug reaction, eosinophilia (≥1.5 x10⁹/l and/or atypical lymphocytes in peripheral blood) and involvement of two or more internal organs (including the skin). The estimated incidence of this syndrome ranges from 1/1000 to 1/10,000 drug exposures and up to 30% mortality.

CASE REPORT

We present a 14-year-old female with a history of complex partial seizures secondary to head trauma. She began treatment with carbamazepine. After 4 weeks she developed fever, generalized rash, adenopathy and multisystem involvement. Following paraclinical studies and evaluation by various specialists, DRESS Syndrome diagnosis was established. The patient was treated with carbamazepine suspension, steroids and gammaglobulin administration with good response and remission of symptoms.

CONCLUSIONS

Immediate withdrawal of the causative drug and initiation of systemic corticosteroids is the mainstay in disease management.

Clinical perspectives in drug safety and adverse drug reactions

Adverse drug reactions (ADRs) remain a common clinical problem since they can mimic many diseases and cause significant morbidity and mortality. Judicious prescribing is important to minimize their occurrence. Apart from the recent identification of a few pharmacogenomic biomarkers for serious reactions, many remain unpredictable. Spontaneous reporting continues to play an important role in pharmacovigilance and the value of astute clinical observation and well-documented reports of suspicions of a causal link cannot be underestimated. Many national reporting schemes have developed considerable experience and expertise over many years and have large ADR databases, which are national assets. Despite advances in pharmacovigilance, numerous deficiencies have been identified; postmarketing surveillance remains the weakest link in the regulatory process. Regulatory authorities have tended to act later rather than sooner in response to safety signals, and this, when combined with under-reporting, may have led to exposure of a large number of patients to drug-related harm before restriction or withdrawal. In an attempt to improve vigilance, international surveillance may benefit by moving from its current passive/reactive mode toward active surveillance systems with a prospective, comprehensive and systematic approach to monitoring, collecting, analyzing and reporting data on ADRs. This will include increased pressure on pharmaceutical companies to conduct postmarketing studies. Such an active/proactive approach, while maintaining focus on ADR detection, could also aim to extend knowledge of safety, such that emerging changes in risk-benefit during a drug's marketed life are effectively communicated to clinicians and patients. Drug safety monitoring and its regulation are now undergoing an overhaul and it is hoped that vigilance, public safety and trust will improve as a result.

Topical promethazine side effects: our experience and review of the literature

Promethazine hydrochloride is a first-generation H1 receptor antagonist, antihistamine, and antiemetic medication that can also have strong sedative effects. The apparent ability of topical H1r/2r antagonists to target epidermal H1/2r was translated into increased efficacy in the treatment of inflammatory dermatoses, likely due to decreased inflammation and enhanced barrier function.

Pharmacovigilance

Any substance that is capable of producing a therapeutic effect can also produce unwanted or adverse effects. It is important to understand the basic concepts related to Adverse Drug Reactions (ADRs): epidemiology, classification, predisposing factors, evaluation parameters, and surveillance methods. Pharmacovigilance is defined as the science and activities relating to the detection, evaluation, understanding, and prevention of ADRs or any other drug-related problems. It involves patients, medical professionals, the pharmaceutical industry, drug regulatory agencies, and academic scientists. Pharmacoinformatics, the application of information technology with regard to the drug design, development, and drug use has played a major role in the appropriate implementation of pharmacovigilance at industry, regulatory, and hospital levels. The functioning of international regulatory agencies and drug safety departments of pharmaceutical industries has been greatly influenced by pharmacoinformatics. Pharmacoinformatics has changed the way in which health care is practiced. Modern information technology can be used by health care professionals for various purposes and, thereby, make a substantial contribution to optimize the quality of medication use in institutions with due importance of safety. Pharmacoinformatics has a major influence in the development of pharmacogenetics and its individual applications including improving drug safety. Pharmacoinformatics will play a major role in the future development and practice of pharmacovigilance. The present chapter is aimed at providing the readers an insight into the importance and basic concepts of pharmacovigilance, and the process involved in it. Application of pharmacoinformatics in improving drug safety at various levels from an industry, regulatory and hospital perspective is discussed.

Drug allergy

Drug allergy encompasses a spectrum of immunologically-mediated hypersensitivity reactions with varying mechanisms and clinical presentations. This type of adverse drug reaction (ADR) not only affects patient quality of life, but may also lead to delayed treatment, unnecessary investigations, and even mortality. Given the myriad of symptoms associated with the condition, diagnosis is often challenging. Therefore, referral to an allergist experienced in the identification, diagnosis and management of drug allergy is recommended if a drug-induced allergic reaction is suspected. Diagnosis relies on a careful history and physical examination. In some instances, skin testing, graded challenges and induction of drug tolerance procedures may be required.

The most effective strategy for the management of drug allergy is avoidance or discontinuation of the offending drug. When available, alternative medications with unrelated chemical structures should be substituted. Cross-reactivity among drugs should be taken into consideration when choosing alternative agents. Additional therapy for drug hypersensitivity reactions is largely supportive and may include topical corticosteroids, oral antihistamines and, in severe cases, systemic corticosteroids. In the event of anaphylaxis, the treatment of choice is injectable epinephrine. If a particular drug to which the patient is allergic is indicated and there is no suitable alternative, induction of drug tolerance procedures may be considered to induce temporary tolerance to the drug.

This article provides a backgrounder on drug allergy and strategies for the diagnosis and management of some of the most common drug-induced allergic reactions, such allergies to penicillin, sulfonamides, cephalosporins, radiocontrast media, local anesthetics, general anesthetics, acetylsalicylic acid (ASA) and non-steroidal anti-inflammatory drugs.

Incidence and cost estimate of treating pediatric adverse drug reactions in Lagos, Nigeria

CONTEXT AND OBJECTIVES

Adverse drug reactions (ADRs) may cause prolonged hospital admissions with high treatment costs. The burden of ADRs in children has never been evaluated in Nigeria. The incidence of pediatric ADRs and the estimated cost of treatment over an 18-month period were determined in this study.

DESIGN AND SETTING

Prospective observational study on children admitted to the pediatric wards of the Lagos State University Teaching Hospital (LASUTH) in Nigeria, between July 2006 and December 2007.

METHODS

Each patient was assessed for ADRs throughout admission. Medical and non-medical costs to the hospital and patient were estimated for each ADR by reviewing the medical and pharmacy bills, medical charts and diagnostic request forms and by interviewing the parents. Cost estimates were performed in 2007 naira (Nigeria currency) from the perspectives of the hospital (government), service users (patients) and society (bearers of the total costs attributable to treating ADRs). The total estimated cost was expressed in 2007 United States dollars (USD).

RESULTS

Two thousand and four children were admitted during the study; 12 (0.6%) were admitted because of ADRs and 23 (1.2%) developed ADR(s) during admission. Forty ADRs were suspected in these 35 patients and involved 53 medicines. Antibiotics (50%) were the most suspected medicines. Approximately 1.83 million naira (USD 15,466.60) was expended to manage all the patients admitted due to ADRs.

CONCLUSIONS

Treating pediatric ADRs was very expensive. Pediatric drug use policies in Nigeria need to be reviewed so as to discourage self-medication, polypharmacy prescription and sales of prescription medicines without prescription.

Using primary care prescribing databases for pharmacovigilance

AIMS

In the UK, adverse drug reactions (ADRs) are responsible for over 6.5% of all hospital admissions, representing a significant morbidity and cost burden to the health service. We aimed to develop an ADR monitoring system capable of identifying the reasons for patient discontinuation of drug therapy within 6 months of the index prescription.

METHODS

Patients first prescribed amlodipine between 1 March 2004 and 28 February 2007 who discontinued their amlodipine medication within 6 months of the index prescription were identified from the practice team information (PTI) database. Once identified, reasons for amlodipine discontinuation were assessed by an electronic database search using relevant Readcodes and key words and by a direct approach to the primary care medical records.

RESULTS

The PTI database identified 995 patients [61.4% females, mean age 65.9 years (SD 12.4 years)] who discontinued amlodipine within 6 months of an index prescription. An electronic search of the database, using Readcodes, identified that 19.4% (193) of patients who discontinued their medication had an ADR recorded in the database. Six (20%) of 30 participating primary care practices, contributing to the PTI database, agreed to be approached directly and supply the reasons for discontinuation for the 51 patients identified as having discontinued amlodipine in their practices. Completed data were returned for all 51 patients, 98% of whom discontinued amlodipine due to an ADR or adverse drug event.

CONCLUSIONS

The results of this study confirm that primary care prescribing databases can be easily used to identify the frequency and nature of ADRs occurring in an ADR-enriched population identified through medication discontinuation.

Ten-year trends in hospital admissions for adverse drug reactions in England 1999-2009

OBJECTIVES

Adverse drug reactions (ADR) are an important cause of morbidity and mortality. We analysed trends in hospital admissions associated with ADRs in English hospitals between 1999 and 2008.

DESIGN

Data from the Hospital Episode Statistics database were examined for all English hospital admissions (1999-2008) with a primary or secondary diagnosis of an ADR recorded.

SETTING

All NHS (public) hospitals in England.

MAIN OUTCOME MEASURES

The number of admissions and in-hospital mortality rate with a primary (codes including 'adverse drug reaction', 'drug-induced', 'due to drug', 'due to medicament' or 'drug allergy') or secondary diagnosis of ADR (ICD-10 Y40-59) were obtained and analysed. Further analysis for the year 2008-2009 was performed with regard to age, gender, proportion aged >65 yrs and total bed-days.

RESULTS

Between 1999 and 2008, there were 557,978 ADR-associated admissions, representing 0.9% of total hospital admissions. Over this period the annual number of ADRs increased by 76.8% (from 42,453 to 75,076), and in-hospital mortality rate increased by 10% (from 4.3% to 4.7%). In 2008, there were 6,830,067 emergency admissions of which 75,076 (1.1%) were drug-related. Systemic agents were most commonly implicated (19.2%), followed by analgesics (13.3%) and cardiovascular drugs (12.9%).There has been a near two-fold increase in nephropathy and cardiovascular consequences secondary to drugs and a 6.8% fall in mental and behavioural disorders due to drugs. Conclusions ADRs have a major impact on public health. Our data suggest the number of ADR admissions has increased at a greater rate than the increase in total hospital admissions; some of this may be due to improved diagnostic coding. However, in-hospital mortality due to ADR admissions also increased during the period. Our findings should prompt policymakers to implement further measures to reduce ADR incidence and their associated in-hospital mortality, and methods to improve the recording of ADRs.

Selecting nonprescription analgesics

Worldwide, there has been an emerging patient demand for access to efficient drugs without consulting a doctor and obtaining a prescription. As a result, there has been an expanding movement of prescription-only drugs to over-the-counter (OTC) status. An increasing number of drugs are becoming available OTC, empowering patients to treat themselves. Where the principle of empowering individuals to treat themselves can fail is when consumers lack the knowledge to do so safely. This potentially applies to the self-selection of analgesic drugs by consumers. When used inappropriately, these drugs pose significant risks. The nonsteroidal antiinflammatory drugs (NSAIDs) are associated with many adverse reactions, interactions, and contraindications in a number of patient groups, even at OTC doses. In particular, in the elderly, the high incidence of cardiovascular and gastrointestinal disease, coupled with age-related decline in renal function and multiple medication use, all warrant extra caution with the use of NSAIDs and make paracetamol the simple analgesic drug of first choice. Despite the possibility of hepatotoxicity in overdose, paracetamol represents a better all-round option for most patients requiring OTC analgesic therapy.

Active-site characteristics of CYP2C19 and CYP2C9 probed with hydantoin and barbiturate inhibitors

Three series of N-3 alkyl substituted phenytoin, nirvanol, and barbiturate derivatives were synthesized and their inhibitor potencies were tested against recombinant CYP2C19 and CYP2C9 to probe the interaction of these ligands with the active sites of these enzymes. All compounds were found to be competitive inhibitors of both enzymes, although the degree of inhibitory potency was generally much greater towards CYP2C19. Inhibitor stereochemistry did not markedly influence K(i) towards CYP2C9, and log P adequately predicted inhibitor potency for this enzyme. In contrast, stereochemistry was an important factor in determining inhibitor potency towards CYP2C19. (S)-(+)-N-3-Benzylnirvanol and (R)-(-)-N-3-benzylphenobarbital emerged as the most potent and selective CYP2C19 inhibitors, with K(i) values of < 250nM--at least two orders of magnitude greater inhibitor potency than towards CYP2C9. Both inhibitors were metabolized preferentially at their C-5 phenyl substituents, indicating that CYP2C19 prefers to orient the N-3 substituents away from the active oxygen species. These features were incorporated into expanded CoMFA models for CYP2C9, and a new, validated CoMFA model for CYP2C19.

Clinical Pharmacology

The dose of a drug is a major determinant of its safety, and establishing a safe dose of a novel drug is a prime objective during clinical development. The design of pre-marketing clinical trials precludes the representation of important subpopulations such as children, the elderly and people with co-morbidities. Therefore, postmarketing surveillance (PMS) activities are required to monitor the safety profile of drugs in real clinical practice. Furthermore, individual variations in pharmacogenetic profiles, the immune system, drug metabolic pathways and drug-drug interactions are also important factors in the occurrence of adverse drug reactions. Thus, the safety of a drug is a major clinical consideration before and after it is marketed. A multidisciplinary approach is required to enhance the safety profile of drugs at all stages of development, including PMS activities. Clinical pharmacology encompasses a range of disciplines and forms the backbone of drug safety consideration during clinical drug development. In this review we give an overview of the clinical drug development process and consider its limitations. We present a discussion of several aspects of clinical pharmacology and their application to enhancing drug safety. Pharmacokinetic-pharmacodynamic modelling provides a method of predicting a clinically safe dose; consideration of drug pharmacokinetics in special populations may enhance safe therapeutics in a wider spectrum of patients, while pharmacogenetics provides the possibility of genotype-specific therapeutics. Pharmacovigilance activities are also discussed. Given the complex nature and unpredictability of type B reactions, PMS activities are crucial in managing the risks drugs pose to the general population. The various aspects of clinical pharmacology discussed make a strong case for this field as the backbone of optimising and promoting safe development and use of drugs.