Clinical pharmacokinetics of vasodilators. Part II

Sublingual and buccal drug administration in medical emergencies

Drug administration is crucial to achieve effective therapeutic drug outcomes. In medical emergencies, it is particularly convenient to use drugs that could be administered as an alternative to traditional routes (as oral or intravenous routes), that are not always suitable in these situations. Thus, sublingual and buccal routes offer an alternative to traditional routes, when a rapid onset of action is required. The main objective of this narrative review is to summarize the evidence for the use of sublingual and buccal drug administration in medical emergencies. The evidence obtained has been divided into four common scenarios found in the emergency department and intensive care units: cardiovascular emergencies, acute pain, agitation, and epileptic status. Moreover, the main advantages and disadvantages of sublingual and buccal routes are presented, as the future perspectives in the drug delivery field to overcome the limitations of these routes.

The impact of pregnancy on antihypertensive drug metabolism and pharmacokinetics: current status and future directions

INTRODUCTION

Hypertensive disorders of pregnancy (HDP) are rising in prevalence, and increase risk of adverse maternal and fetal outcomes. Physiologic changes occur during pregnancy that alter drug pharmacokinetics. However, antihypertensive drugs lack pregnancy-specific dosing recommendations due to critical knowledge gaps surrounding the extent of gestational changes in antihypertensive drug pharmacokinetics and underlying mechanisms.

AREAS COVERED

This review (1) summarizes currently recommended medications and dosing strategies for non-emergent HDP treatment, (2) reviews and synthesizes existing literature identified via a comprehensive Pubmed search evaluating gestational changes in the maternal pharmacokinetics of commonly prescribed HDP drugs (notably labetalol and nifedipine), and (3) offers insight into the metabolism and clearance mechanisms underlying altered HDP drug pharmacokinetics during pregnancy. Remaining knowledge gaps and future research directions are summarized.

EXPERT OPINION

A series of small pharmacokinetic studies illustrate higher oral clearance of labetalol and nifedipine during pregnancy. Pharmacokinetic modeling and preclinical studies suggest these effects are likely due to pregnancy-associated increases in hepatic UGT1A1- and CYP3A4-mediated first-pass metabolism and lower bioavailability. Accordingly, higher and/or more frequent doses may be needed to lower blood pressure during pregnancy. Future research is needed to address various evidence gaps and inform the development of more precise antihypertensive drug dosing strategies.

Molsidomine alleviates acetic acid-induced colitis in rats by reducing oxidative stress, inflammation and apoptosis

Ulcerative colitis (UC) is a subcategory of intestinal inflammatory bowel disease characterized by up-regulation of proinflammatory cytokines and oxidative stress. The current study was designed to assess the probable protective effect of the nitric oxide (NO) donor, molsidomine, in experimental colitis model in rats. Rats were haphazardly classified into four groups: control, acetic acid, acetic acid + molsidomine (1 mg/kg) and acetic acid + molsidomine (2 mg/kg). Molsidomine (1 and 2 mg/kg/day) was administered by intra-peritoneal injection for 7 days prior to induction of UC. On the 8th day, colitis was induced by intra-rectal instillation of 2 ml of (4% v/v) acetic acid in normal saline using a pediatric plastic catheter. The rats were sacrificed 1 day following colitis induction, blood samples were obtained; colons and livers were isolated then underwent macroscopic, biochemical, histopathological and immunohistochemical examination. Pretreatment with molsidomine significantly reduced disease activity index, colon mass index, colonic macroscopic and histological damage. Besides, molsidomine significantly reduced the serum levels of alanine transaminase (ALT) (58.7 ± 8.9 & 59.7 ± 8 vs 288.75 ± 31.4 in AA group) and aspartate transaminase (AST) (196.2 ± 37.4 & 204 ± 30 vs 392.7 ± 35.6 in AA group). Moreover, molsidomine effectively decreased malondialdehyde (MDA) and total nitrate/nitrite (NOx) contents, and up regulated the enzymatic activity of superoxide dismutase (SOD) and glutathione level (GSH) in colonic and hepatic tissues. With regard to anti-inflammatory mechanisms, molsidomine suppressed tumor necrosis factor-alpha (TNF-α) (792.5 ± 16.7 & 448 ± 12.1 vs 1352.5 ± 45.8 in AA group) in colonic tissues and (701 ± 19 & 442.5 ± 22.5 vs 1501 ± 26 in AA group) in hepatic tissues as well as nuclear transcription factor kappa B (NF-kB/p65) levels (416.2 ± 4.1 & 185.5 ± 14.2 vs 659.2 ± 11.5 in AA group) in colonic tissues and (358 ± 6.2 & 163.5 ± 9.6 vs 732.5 ± 5.5 in AA group) in hepatic tissues. In addition, molsidomine significantly decreased inducible nitric oxide synthase (iNOS) levels (8.1 ± 0.1 & 4.9 ± 0.1 vs 16 ± 0.1 in AA group) in colonic tissues and (8.6 ± 0.3 & 6.1 ± 0.1 vs 17.8 ± 0.1 in AA group) in hepatic tissues, and myeloperoxidase (MPO) contents (10.5 ± 0.4 & 6.6 ± 0.3 vs 20.9 ± 0.6 in AA group) in colonic tissues and (13.1 ± 0.2 & 6.3 ± 0.06 vs 23.9 ± 1.4 in AA group) in hepatic tissues at p > 0.05. Furthermore, it suppressed apoptosis by reducing expression of Caspase 3 and Bax in colonic and hepatic tissues. Therefore, molsidomine might be a promising candidate for the treatment of UC.

Vasodilatation by carbon dioxide and sodium nitroglycerin reduces compliance of the cerebral arteries in humans

NEW FINDINGS

What is the central question of this study? Vascular compliance importantly contributes to the regulation of cerebral perfusion and complex mechanisms are known to influence compliance of a vascular bed: while vasodilatation mediates changes in vascular resistance, does it also affect compliance, particularly in the cerebral vasculature? What is the main finding and its importance? Cerebral vasodilatation, elicited by hypercapnia and sodium nitroglycerin administration, reduced cerebrovascular compliance by approximately 26% from baseline. This study provides new insight into mechanisms mediating cerebrovascular compliance.

ABSTRACT

Changes in vascular resistance and vascular compliance contribute to the regulation of cerebral perfusion. While changes in vascular resistance are known to be mediated by vasodilatation, the mechanisms contributing to changes in vascular compliance are complex. In particular, whether vasodilatation affects compliance of the vasculature within the cranium remains unknown. Therefore, the present study examined the impact of two vasodilatation pathways on cerebrovascular compliance in humans. Fifteen young, healthy adults (26 ± 5 years, seven females) completed two protocols: (i) sublingual sodium nitroglycerin (SNG; 0.4 mg) and (ii) hypercapnia (5-6% carbon dioxide gas mixture for 4 min). Blood pressure waveforms (finger photoplethysmography) and middle cerebral artery blood velocity waveforms (transcranial Doppler ultrasound) were input into a modified Windkessel model and an index of cerebrovascular compliance (Ci) was calculated. During the SNG protocol, Ci decreased 24 ± 17% from baseline ((5.0 ± 2.3) × 10^-4  cm s^-1  mmHg^-1 ) to minute 10 ((3.6 ± 1.2) × 10^-4  cm s^-1  mmHg^-1 ; P = 0.009). During the hypercapnia protocol, Ci decreased 28 ± 9% from baseline ((4.4 ± 1.9) × 10^-4  cm s^-1  mmHg^-1 ) to minute 4 ((3.1 ± 1.4) × 10^-4  cm s^-1  mmHg^-1 ; P < 0.001). Cerebral vasodilatory stimuli induced by nitric oxide and carbon dioxide mechanisms reduced compliance of the cerebral vascular bed by approximately 26% from supine baseline values.

Pregnancy-Related Hormones Increase UGT1A1-Mediated Labetalol Metabolism in Human Hepatocytes

Pregnancy-related hormones (PRH) are recognized as important regulators of hepatic cytochrome P450 enzyme expression and function. However, the impact of PRH on the hepatic expression and function of uridine diphosphate glucuronosyltransferases (UGTs) remains unclear. Using primary human hepatocytes, we evaluated the effect of PRH exposure on mRNA levels and protein concentrations of UGT1A1, UGT2B7, and other key UGT enzymes, and on the metabolism of labetalol (a UGT1A1 and UGT2B7 substrate commonly prescribed to treat hypertensive disorders of pregnancy). Sandwich-cultured human hepatocytes (SCHH) from female donors were exposed to the PRH estradiol, estriol, estetrol, progesterone, and cortisol individually or in combination. We quantified protein concentrations of UGT1A1, UGT2B7, and four additional UGT1A isoforms in SCHH membrane fractions and evaluated the metabolism of labetalol to its glucuronide metabolites in SCHH. PRH exposure increased mRNA levels and protein concentrations of UGT1A1 and UGT1A4 in SCHH. PRH exposure also significantly increased labetalol metabolism to its UGT1A1-derived glucuronide metabolite in a concentration-dependent manner, which positively correlated with PRH-induced changes in UGT1A1 protein concentrations. In contrast, PRH did not alter UGT2B7 mRNA levels or protein concentrations in SCHH, and formation of the UGT2B7-derived labetalol glucuronide metabolite was decreased following PRH exposure. Our findings demonstrate that PRH alter expression and function of UGT proteins in an isoform-specific manner and increase UGT1A1-mediated labetalol metabolism in human hepatocytes by inducing UGT1A1 protein concentrations. These results provide mechanistic insight into the increases in labetalol clearance observed in pregnant individuals.

An electrochemical investigation into the effects of local and systemic administrations of sodium nitroprusside in brain extracellular fluid of mice

Sodium nitroprusside (SNP) is a nitric oxide (NO)-donor drug used clinically to treat severe hypertension, however, there are limitations associated with its mechanism of action that prevent widespread adoption. In particular, its impact on cerebral hemodynamics is controversial and direct evidence on its effects are lacking. Electrochemical methods provide an attractive option to undertake real time neurochemical measurements in situ using selective microsensors. Herein, we report the novel application of an existing platinum (Pt)-Nafion® sensor to measure the release of NO from SNP under in vitro and in vivo conditions. Initially, the temporal release of NO was measured and the effect of the reducing agent, ascorbic acid (AA), was elucidated in vitro. A combined microdialysis/NO sensor construct was implanted into the striatum of anaesthetised mice and the local perfusion of 10 mM SNP with/without AA resulted in increased NO concentration detected using the Pt-Nafion® sensor. Subsequently, the NO sensor, coupled with carbon paste electrodes (CPEs) for the electrochemical measurement of O₂, were applied to investigate SNP effects in freely moving mice. A complex mechanism of action was identified that infers NO inhibition and biphasic O₂ dynamics. The preliminary findings within support a strong cerebrovascular effect of systemic SNP administration that warrants careful consideration for clinical use.

Phentolamine Reverses Epinephrine-Enhanced Skin Antinociception of Dibucaine in Rats

BACKGROUND

The objective of the experiment was to assess the antinociceptive effect of dibucaine, bupivacaine, and epinephrine. To assess the mechanism of action of the interaction between dibucaine and epinephrine, phentolamine, a nonselective α-adrenergic antagonist, was added to the mixture.

METHODS

We assessed sensory blockade with these drugs by injecting 0.6 mL of drug-in-saline in the dorsal thoracolumbar area of rats; pinprick of the "wheal" formed by the injectate was the area targeted for stimulation to elicit a cutaneous trunci muscle reflex. The sensory block of dibucaine was compared with that of bupivacaine or epinephrine. Drug-drug interactions were analyzed by isobologram. Phentolamine was added to investigate the antinociceptive effect of dibucaine coinjected with epinephrine.

RESULTS

We demonstrated that dibucaine, epinephrine, and bupivacaine produced dose-dependent skin antinociception. On the median effective dose (ED50) basis, the potency was higher for epinephrine (mean, 0.011 [95% confidence interval {CI}, 0.007-0.015] μmol) than for dibucaine (mean, 0.493 [95% CI, 0.435-0.560] μmol) (P < .01), while there were no significant differences between dibucaine and bupivacaine (mean, 0.450 [95% CI, 0.400-0.505] μmol). On the equipotent basis (75% effective dose, median effective dose, and 25% effective dose), sensory block duration provoked by epinephrine was greater (P < .01) than that provoked by dibucaine or bupivacaine. Coadministration of dibucaine with epinephrine produced a synergistic nociceptive block, whereas phentolamine blocked that synergistic block.

CONCLUSIONS

The preclinical data indicated that there is no statistically significant difference between the potency and duration of dibucaine and bupivacaine in this model. Epinephrine synergistically enhances the effects of dibucaine, while phentolamine partially blocked those effects. α-Adrenergic receptors play an important role in controlling synergistic analgesic effect of dibucaine combined with epinephrine.

Sodium nitroglycerin induces middle cerebral artery vasodilatation in young, healthy adults

NEW FINDINGS

What is the central question of this study? Nitric oxide causes dilatation in peripheral vessels; however, whether nitric oxide affects basal cerebral artery dilatation has not been explored. What is the main finding and its importance? This study demonstrated that vasodilatation occurs in the right middle cerebral artery in response to exogenous nitric oxide. However, blood velocity decreased and, therefore, overall cerebral blood flow remained unchanged. This study provides new insight into the role of nitric oxide in cerebral blood flow control.

ABSTRACT

Recent evidence indicates that basal cerebral conduit vessels dilate with hypercapnia, with a nitric oxide (NO) mechanism explaining one way in which parenchymal cerebral arterioles dilate. However, whether NO affects basal cerebral artery dilatation remains unknown. This study quantified the effect of an exogenous NO donor [sodium nitroglycerin (NTG); 0.4 mg sublingual spray] on the right middle cerebral artery (rMCA) cross-sectional area (CSA), blood velocity and overall blood flow. Measures of vessel CSA (7 T magnetic resonance imaging) and MCA blood velocity (transcranial Doppler ultrasound) were made at baseline (BL) and after exogenous NTG or placebo (PLO) administration in young, healthy individuals (n = 10, two males, age range 20-23 years). The CSA increased in the rMCA [BL, 5.2 ± 1.2 mm² ; PLO, 5.4 ± 1.5 mm² ; NTG, 6.6 ± 1.5 mm² , P < 0.05; mean ± SD]. Concurrently, rMCA blood velocity decreased from BL during NTG compared with PLO (BL, 67 ± 10 cm s^-1 ; PLO, 62 ± 10 cm s^-1 ; NTG, 59 ± 9.3 cm s^-1 , P < 0.05; mean ± SD]. However, total MCA blood flow did not change with NTG or PLO [BL, 221 ± 37.4 ml min^-1 ; PLO, 218 ± 35.0 ml min^-1 ; NTG, 213 ± 46.4 ml min^-1 ). Therefore, exogenous NO mediates a dilatory response in the rMCA, but not in its downstream vascular bed.

[Which medications are safe while breastfeeding? : A synopsis for the anesthetist, obstetrician and pediatrician]

Pharmacokinetic data on drug administration during lactation are often inconsistent or missing. For legal reasons medicinal drug product information generally advises to interrupt breastfeeding for 24 h after medication intake. However this is not standard of care in clinical practice as the mother should be instructed to initiate breastfeeding as soon as possible after giving birth. At the same time the medication exposure over the breast milk for the newborn should be minimized. Aim of this article is to summarize pharmacokinetic data and to give important clinical information on medications frequently administered during the lactation period. As a general rule a mother can start breastfeeding following anesthesia as soon as she is able to get her baby latched on her breast.

Medications and Breast-Feeding: A Guide for Pharmacists, Pharmacy Technicians, and other Healthcare Professionals Part II

Objective:

To provide a guide for practicing pharmacists, pharmacy technicians, and other healthcare professionals so that they are able to counsel and advise breast-feeding mothers and fellow healthcare professionals on the safety and use of common cardiology and general medications during breast-feeding.

Data Sources:

Primary texts used by the breast-feeding community ( Medications and Mothers' Milk, Drugs in Pregnancy and Lactation, Drugs and Human Lactation) were searched, as well as Micromedex, MEDLINE, PubMed, EMBASE, and EMBASE2 (1984–February 2004).

Study Selection/Data Extraction:

Multiple sources were used wherever available to validate the data, and primary articles were used to verify all tertiary source information. Search terms included breast-feeding, lactation, nursing, and medications, as well as specific drug names.

Data Synthesis:

Concerns regarding medication use during breast-feeding have caused mothers to either discontinue nursing or not take necessary medications. Complete avoidance of medications or cessation of breast-feeding is often unnecessary. Although there are drugs that can be harmful to nursing infants, breast milk concentrations of most drugs are insufficient to cause any harm.

Conclusions:

Having objective and reliable information on medications enables pharmacists, pharmacy technicians, healthcare providers, and mothers to make educated decisions regarding drug therapy and breast-feeding.

A review of oral labetalol and nifedipine in mild to moderate hypertension in pregnancy

Hypertension is the most commonly encountered medical condition in pregnancy, contributing significantly to maternal and perinatal morbidity and mortality. Mild to moderate hypertension in pregnancy is defined as systolic blood pressure of 140-159 mmHg or diastolic blood pressure of 90-109 mmHg (7-9% of pregnancies). When treating hypertension in pregnancy, not only do physiologic changes of pregnancy have an effect on the pharmacokinetics and pharmacodynamics of the drugs used, but the pathophysiology of hypertensive disorders of pregnancy also have an effect. To date, evidence is lacking on the pharmacokinetics and pharmacodynamics of commonly used antihypertensive drugs, which often times leads to suboptimal treatment of hypertensive pregnant women. When considering which agents to use for treatment of mild to moderate hypertension, specifically in gestational and chronic hypertension, oral labetalol and nifedipine are valid options. An overview of the profile for use, safety, and current pharmacokinetic data for each agent is presented here.

Evaluation of fasted and fed state simulated and human intestinal fluids as solvent system in the Ussing chambers model to explore food effects on intestinal permeability

The Ussing chambers model is almost exclusively used in the presence of plain aqueous phosphate buffers as solvent system. In an attempt to further elucidate the effect of luminal ingredients and postprandial conditions on intestinal permeability, pooled fasted and fed state human intestinal fluids (FaHIFpool, FeHIFpool) were used. In addition, simulated intestinal fluids of both nutritional states (FaSSIF, FeSSIF) were evaluated as possible surrogate media for HIF. The use of FaHIFpool generated a broad range of Papp values for a series of 16 model drugs, ranging from 0.03×10(-6)cm/s (carvedilol) to 33.8×10(-6)cm/s (naproxen). A linear correlation was observed between Papp values using FaSSIF and FaHIFpool as solvent system (R=0.990), justifying the use of FaSSIF as surrogate medium for FaHIF in the Ussing chambers. In exclusion of the outlier carvedilol, a strong sigmoidal relationship was found between Papp and fahuman of 15 model drugs, illustrated by correlation coefficients of 0.961 and 0.936 for FaHIFpool and FaSSIF, respectively. When addressing food effects on intestinal permeability, the use of FeHIFpool resulted in a significantly lower Papp value for nine out of sixteen compounds compared to fasting conditions. FeSSIF as solvent system significantly overestimated Papp values in FeHIFpool. To conclude, the optimized Ussing chambers model using biorelevant media as apical solvent system holds great potential to investigate food effects in a more integrative approach, taking into account drug solubilisation, supersaturation and formulation effects.

Evaluation of fasted state human intestinal fluid as apical solvent system in the Caco-2 absorption model and comparison with FaSSIF

To date, the Caco-2 model is considered as the gold standard to predict intestinal drug absorption. Often, aqueous phosphate buffers are used as apical medium. The purpose of this study was to use fasted state human intestinal fluid (FaHIF) as apical solvent system to generate biorelevant permeability values for a series of 16 model drugs that can be used as reference data to critically evaluate fasted state simulated intestinal fluid (FaSSIF) as possible substitute medium. Caco-2 compatibility with FaHIF was achieved when 50mg/ml mucus was applied on top of the cells before adding the apical medium. The use of FaHIF as solvent system generated a broad range of apparent permeability values (Papp) for the series of model compounds. When Papp values obtained with FaHIF were compared to those obtained with FaSSIF, a strong correlation was observed (R=0.951). The use of FaSSIF in the absence of mucus did not significantly alter this correlation. For FaHIF, FaSSIF and reference phosphate buffer blank FaSSIF, a strong sigmoidal relationship was found between Papp and fahuman, illustrated by correlation coefficients of 0.961, 0.893 and 0.868, respectively. In terms of inter-subject variability, the use of FaHIF from different volunteers originating from two distinct age groups (18-25 years; 65-72 years) exhibited an average coefficient of variance (CV) of 30%. However, no age dependency in permeability could be observed. In conclusion, the data generated in this article justify the use of FaSSIF as biorelevant apical medium in the Caco-2 assay to accurately predict in vivo drug absorption. Also, the optimized mucus-containing Caco-2 model can be used in combination with intestinal fluid samples aspirated after drug administration to further investigate intraluminal drug and formulation behavior.

Effect of nitric oxide on spinal evoked potentials and survival rate in rats with decompression sickness

Nitric oxide (NO) releasing agents have, in experimental settings, been shown to decrease intravascular nitrogen bubble formation and to increase the survival rate during decompression sickness (DCS) from diving. The effect has been ascribed to a possible removal of preexisting micronuclei or an increased nitrogen washout on decompression through augmented blood flow rate. The present experiments were conducted to investigate whether a short- or long-acting NO donor [glycerol trinitrate (GTN) or isosorbide-5-mononitrate (ISMN), respectively] would offer the same protection against spinal cord DCS evaluated by means of spinal evoked potentials (SEPs). Anesthetized rats were decompressed from a 1-h hyperbaric air dive at 506.6 kPa (40 m of seawater) for 3 min and 17 s, and spinal cord conduction was studied by measurements of SEPs. Histological samples of the spinal cord were analyzed for lesions of DCS. In total, 58 rats were divided into 6 different treatment groups. The first three received either saline (group 1), 300 mg/kg iv ISMN (group 2), or 10 mg/kg ip GTN (group 3) before compression. The last three received either 300 mg/kg iv ISMN (group 4), 1 mg/kg iv GTN (group 5), or 75 μg/kg iv GTN (group 6) during the dive, before decompression. In all groups, decompression caused considerable intravascular bubble formation. The ISMN groups showed no difference compared with the control group, whereas the GTN groups showed a tendency toward faster SEP disappearance and shorter survival times. In conclusion, neither a short- nor long-acting NO donor had any protective effect against fatal DCS by intravenous bubble formation. This effect is most likely due to a fast ascent rate overriding the protective effects of NO, rather than the total inert tissue gas load.

Comparative short-term effect of once-daily molsidomine on chronic angina in general practitioners' versus cardiologists' coronary patient populations

INTRODUCTION

The direct nitric oxide donor molsidomine is commonly used to relieve symptoms in chronic angina thanks to its vasodilatory properties that induce both a reduction in myocardial oxygen demand and an increase in coronary blood flow. The objective of this study was to compare the short-term effect of molsidomine 16 mg once daily (Coruno(®), Therabel Pharmaceuticals Ltd, Dublin, Ireland) in patients with stable angina previously on molsidomine 8 mg twice daily, in care of general practitioners (GPs) versus cardiologists.

METHODS

A total of 53 and 80 patients treated by GPs and cardiologists, respectively, took part in this multicenter, open-label clinical trial. Frequency of anginal attacks, short-acting nitroderivative tablets consumption, and subjective clinical status were evaluated, as was tolerability to molsidomine through the reporting of adverse events (AEs), the recording of vital parameters-resting blood pressure, heart rate, and electrocardiogram-and routine blood analyses.

RESULTS

Although demographic and clinical characteristics were significantly different in GPs' compared with cardiologists' patients, the effect of either the 8 mg or the 16 mg molsidomine formulation on anginal crises and nitroderivatives consumption was similar in both patient cohorts, with a trend for the 16 mg formulation to be more efficient on symptoms in elderly patients. Subjective assessment of the beneficial effect of molsidomine 16 versus 8 mg was comparable in GPs' and cardiologists' patients independently of age, "no change" being the most often reported item. Self-evaluation of functional capacity in elderly showed on the whole no difference between the two patient cohorts, only magnitude of pace and total score on molsidomine 16 mg being higher in cardiologists' compared with GPs' patients, and total score in cardiologists' patients higher on molsidomine 16 mg compared with 8 mg. Incidences of AEs and drug-related AEs, as well as proportions of patients reporting such AEs, were similar between GPs' and cardiologists' patient cohorts as between molsidomine 8 and 16 mg formulations. Molsidomine 16 mg once daily had no clinically significant effect on blood pressure, heart rate, electrocardiogram or blood parameters, and compliance with treatment was excellent in whatever patient cohort.

CONCLUSION

Despite significant demographic and clinical differences between patients in care of GPs and cardiologists, molsidomine was equally efficient in these two patient cohorts, with a trend towards less anginal attacks in the elderly when treated with the 16 mg compared with the 8 mg formulation. Compliance and tolerability to the drug were excellent in both patient cohorts.

The effect of sodium nitroprusside on cerebral hemodynamics and headache in healthy subjects

Investigation

Sodium nitroprusside (SNP) is a powerful vasodilatory agent that, similarly to glyceryl trinitrate (GTN), releases nitric oxide (NO) but in contrast does not pass the blood-brain barrier. Nevertheless, it has already been used in animal models without any knowledge of its headache-inducing potential. We hypothesized that SNP would induce headache and vasodilation of cephalic and radial but not cerebral arteries.

Methods

Five healthy volunteers received intravenous infusions of SNP in a non-randomized dose-titration (1–5 µg/kg/min) study. We recorded headache intensity (verbal rating scale from 0 to 10), velocity in the middle cerebral artery (VMCA), and diameters of the superficial temporal artery (STA) and radial artery (RA).

Results

All participants reported a dose-related headache (median peak = 2.5, range 0–3). SNP dilated the STA and RA, caused a marked increase of heart rate and a decrease of mean arterial pressure (MAP) and partial pressure of end-tidal carbon dioxide (PetCO2). We found that SNP decreased the velocity of the VMCA, but this was canceled by a decrease of cerebral blood flow (CBF) due to hypocapnia.

Conclusion

The present study shows that SNP is a headache-inducing agent with close similarities to headaches induced by GTN and probably without effect on intracerebral arteries.

Understanding the oral mucosal absorption and resulting clinical pharmacokinetics of asenapine

Absorption of drugs from the oral cavity into the mucosal tissues is typically a fast event. Dissolved drugs partition into the mucosal membranes and within minutes will reach equilibrium with drug in solution in the oral cavity. However, this does not always equate to rapid drug appearance in the systemic circulation. This has been attributed to slow partitioning out of the mucosal tissues and into the systemic circulation. Based on information from literature, physicochemical properties of asenapine, and clinical data, we conclude that for sublingually administered asenapine, the exposure is primarily a function of rapid partitioning into the mucosal membranes. This is followed by slow partitioning out of the mucosal tissues and into the systemic circulation, leading to a T (max) value of about 1 h. The bioavailability of asenapine at doses below the saturation solubility in the mouth does not change and is controlled primarily by mass transport equilibrium. At doses above the saturation solubility, the bioavailability becomes more dependent not only on the distribution equilibrium but also on contact time in the mouth because additional variables (e.g. dissolution rate of the drug) need to be accounted for. These explanations are consistent with oral cavity absorption models from the literature and can be used to accurately describe the clinical data for asenapine.

Therapeutic and toxic blood concentrations of nearly 1,000 drugs and other xenobiotics

INTRODUCTION

In order to assess the significance of drug levels measured in intensive care medicine, clinical and forensic toxicology, as well as for therapeutic drug monitoring, it is essential that a comprehensive collection of data is readily available. Therefore, it makes sense to offer a carefully referenced compilation of therapeutic and toxic plasma concentration ranges, as well as half-lives, of a large number of drugs and other xenobiotics for quick and comprehensive information.

METHODS

Data have been abstracted from original papers and text books, as well as from previous compilations, and have been completed with data collected in our own forensic and clinical toxicology laboratory. The data presented in the table and corresponding annotations have been developed over the past 20 years and longer. A previous compilation has been completely revised and updated. In addition, more than 170 substances, especially drugs that have been introduced to the market since 2003 as well as illegal drugs, which became known to cause intoxications, were added. All data were carefully referenced and more than 200 new references were included. Moreover, the annotations providing details were completely revised and more than 100 annotations were added.

RESULTS

For nearly 1,000 drugs and other xenobiotics, therapeutic ("normal") and, if data were available, toxic and comatose-fatal blood-plasma concentrations and elimination half-lives were compiled in a table.

CONCLUSIONS

In case of intoxications, the concentration of the ingested substances and/or metabolites in blood plasma better predicts the clinical severity of the case when compared to the assumed amount and time of ingestion. Comparing and contrasting the clinical case against the data provided, including the half-life, may support the decision for or against further intensive care. In addition, the data provided are useful for the therapeutic monitoring of pharmacotherapies, to facilitate the diagnostic assessment and monitoring of acute and chronic intoxications, and to support forensic and clinical expert opinions.

Paradoxical and bidirectional drug effects

A paradoxical drug reaction constitutes an outcome that is opposite from the outcome that would be expected from the drug's known actions. There are three types: 1. A paradoxical response in a condition for which the drug is being explicitly prescribed. 2. Paradoxical precipitation of a condition for which the drug is indicated, when the drug is being used for an alternative indication. 3. Effects that are paradoxical in relation to an aspect of the pharmacology of the drug but unrelated to the usual indication. In bidirectional drug reactions, a drug may produce opposite effects, either in the same or different individuals, the effects usually being different from the expected beneficial effect. Paradoxical and bidirectional drug effects can sometimes be harnessed for benefit; some may be adverse. Such reactions arise in a wide variety of drug classes. Some are common; others are reported in single case reports. Paradoxical effects are often adverse, since they are opposite the direction of the expected effect. They may complicate the assessment of adverse drug reactions, pharmacovigilance, and clinical management. Bidirectional effects may be clinically useful or adverse. From a clinical toxicological perspective, altered pharmacokinetics or pharmacodynamics in overdose may exacerbate paradoxical and bidirectional effects. Certain antidotes have paradoxical attributes, complicating management. Apparent clinical paradoxical or bidirectional effects and reactions ensue when conflicts arise at different levels in self-regulating biological systems, as complexity increases from subcellular components, such as receptors, to cells, tissues, organs, and the whole individual. These may be incompletely understood. Mechanisms of such effects include different actions at the same receptor, owing to changes with time and downstream effects; stereochemical effects; multiple receptor targets with or without associated temporal effects; antibody-mediated reactions; three-dimensional architectural constraints; pharmacokinetic competing compartment effects; disruption and non-linear effects in oscillating systems, systemic overcompensation, and other higher-level feedback mechanisms and feedback response loops at multiple levels. Here we review and provide a compendium of multiple class effects and individual reactions, relevant mechanisms, and specific clinical toxicological considerations of antibiotics, immune modulators, antineoplastic drugs, and cardiovascular, CNS, dermal, endocrine, musculoskeletal, gastrointestinal, haematological, respiratory, and psychotropic agents.

Medications in pregnancy and lactation: Part 2. Drugs with minimal or unknown human teratogenic effect

This is the second of a two-part series on the use of medication during pregnancy and lactation. Pregnancy risk factors together with an increased incidence of chronic diseases and the rise in mean maternal age predict an increase in medication use during gestation. However, as highlighted in the first installment of this series, relatively few medications have specifically been tested for safety and efficacy during pregnancy, and, therefore, responses to those inquiries can be uninformed and inaccurate. Whereas the first installment provided new insight into the nature of medications with known human teratogenic effects, this part concentrates on drugs with minimal or no known human teratogenic effect. It is important that clinicians become familiar with all of the aspects of the drugs they prescribe, in addition to the controversies surrounding them, through consultation with maternal-fetal medicine specialists and through references and Web sites providing up-to-date information in an effort to promote safer prescribing practices.

Comparative effects of once-daily molsidomine in coronary patients from two distinct European ethnicities

INTRODUCTION

Molsidomine, a direct nitric oxide donor, is frequently used in several European countries for the treatment of stable angina. The aim of this study was to compare the effects of a new once-daily 16-mg dose formulation, Coruno (Therabel Pharmaceuticals, Loughrea, Ireland), in patients with stable angina belonging to two distinct European ethnicities.

METHODS

A total of 261 Hungarian and 267 Polish patients took part in this multicenter, randomized, double-blind, placebo-controlled clinical trial. Exercise testing was performed after the first administration of molsidomine and repeated after a 2-week treatment. Frequency of anginal attacks, short-acting nitroderivative tablet consumption, and incidence of adverse events were also evaluated.

RESULTS

Demographic and clinical characteristics were significantly different in Hungarian compared with Polish patients. Hungarian patients had a lower proportion of males, were shorter in stature, had less previous smoking experience, consumed more alcohol, had less severe coronary disease (electrocardiographic evidence, rate of anginal crises, and nitroderivative consumption), and higher exercise capacity. However, molsidomine-related improvement in exercise capacity at start of the study was similar in both cohorts. After a 2-week treatment, improvement was fully maintained in Polish and only minimally reduced in Hungarian patients. Furthermore, molsidomine reduced significantly more anginal episodes and nitroderivative consumption in the more severely affected Polish cohort. Proportions of patients reporting drug-related adverse events were similar on placebo and molsidomine in both cohorts. Most of the adverse events were not severe and resolved spontaneously. Less myocardial ischemia and gender (including height, a confounding covariate) acted positively and negatively, respectively, on the higher exercise capacity of Hungarian versus Polish patients.

CONCLUSION

The once-daily 16-mg molsidomine formulation is effective and has good tolerability in both patient cohorts. Molsidomine does not induce any meaningful tolerance issues in Hungarian or Polish patients with stable angina, despite significant demographic and clinical disparities.

Hydralazine inhibits human cervical cancer cell growth in vitro in association with APC demethylation and re-expression

PURPOSE

The tumor suppressor adenomatous polyposis coli (APC) is frequently silenced by promoter hypermethylation in human cervical cancer. Clinically, it has been approved that DNA methylation inhibitors, such as 5-aza-2'-deoxycytidine (5-Aza-dC), can reverse APC promoter methylation, but widespread clinical use of these inhibitors is limited by their toxicity and instability in aqueous solution. Hydralazine is a stable DNA methylation inhibitor that has minimal toxicity in vitro and in vivo. The purpose of this study was to evaluate the effects of hydralazine on APC reactivation and the inhibition of human cervical cancer cells in vitro.

METHODS

Expression of APC gene, and methylation status were analyzed by RT-PCR, quantitative real time RT-PCR, and methylation-specific PCR methods. beta-Catenin protein that correlates closely with APC was detected by immunohistochemistry method after treatment with hydralazine. MTT and FCM assays were used to observe the changes of proliferation activity, cell cycle, and apoptosis of the cells.

RESULTS

Methylated APC was not expressed in HeLa cell, hemimethylated APC was expressed in CaSki cells, and unmethylated APC was expressed normally in SiHa cells. Hydralazine induces APC expression and promotes demethylation in HeLa and CaSki cells. After treatment with 40 mumol/L hydralazine for 72 h, growth inhibitive rates (%) of HeLa, CaSki, and SiHa cell lines were 52.12 +/- 3.78, 44.31 +/- 2.59, and 47.73 +/- 4.73, respectively. On the contrary, the normal cell ECV304 growth inhibitory rate was only 27.18 +/- 0.79. The expression of APC mRNA in HeLa, CaSki, and SiHa cell lines increased 10.35-, 11.40-, and 0.73-fold, respectively. HeLa and CaSki cells were arrested in S phase of the cell cycle by hydralazine, and the percentage of apoptotic cells in the two cell lines treated with hydralazine was increased significantly compared to the untreated cells (P < 0.01). The expression of beta-catenin protein in the cell membrane was observed after the treatment with hydralazine.

CONCLUSIONS

Hydralazine, an effective inhibitor of APC methylation and promoter of APC re-expression, can inhibit cell growth in human cervical cancer in vitro and be potentially used for the clinical treatment of human cervical cancer.

BiDil (isosorbide dinitrate and hydralazine): a new fixed-dose combination of two older medications for the treatment of heart failure in black patients

BiDil is a new fixed-dose combination of 2 older medications, isosorbide dinitrate (ISDN) and hydralazine. ISDN is an organic nitrate that is biotransformed into nitric oxide, a potent vasodilator. Hydralazine is believed to have both vasodilatory properties specific to the arteries and antioxidant properties, which address both the biochemical alterations in the failing cardiovascular system as well as the issue of nitrate tolerance. A drug regimen combining an NO stimulator (ISDN) with an antioxidant (hydralazine) favorably influences the nitroso-redox balance. Retrospective analyses of previous heart failure (HF) clinical trials comparing the combination of ISDN and hydralazine with placebo and enalapril, respectively, demonstrated a benefit in the black population, setting the precedent for a race-based therapeutic study, the African-American Heart Failure Trial (A-HeFT). A-HeFT examined the use of BiDil added to standard HF therapy in blacks with New York Heart Association functional class III and IV HF. BiDil demonstrated a 43% reduction in mortality when compared with placebo. As a result, current evidence-based treatment guidelines recommend that the addition of ISDN and hydralazine in black patients with moderate to severe HF optimized on standard therapy be considered. BiDil is currently indicated for the treatment of HF as an adjunct to standard therapy in black patients. The use of BiDil for black patients with mild disease or in nonblack patients with HF has not been studied. Future clinical trials involving an ethnically and clinically diverse population of patients would further define the role of combined ISDN and hydralazine in the treatment of HF.

Case report: Profound hypotension associated with labetalol therapy in a patient with cerebral aneurysms and subarachnoid hemorrhage

PURPOSE

Labetalol is an effective antihypertensive medication frequently used to treat systemic hypertension in acute care settings, including the management of hypertension associated with a subarachnoid hemorrhage. We present a case of profound hypotension, refractory to inotropic and vasopressor therapy following an iv infusion of labetalol.

CLINICAL FEATURES

Initiation of an iv labetalol infusion resulted in good blood pressure control in a patient suffering from a Fisher grade 3 subarachnoid hemorrhage with an initial Glascow coma scale of 14/15 and mild hydrocephalus. Progressive deterioration of neurological symptoms and evidence of worsening hydrocephalus preceded the sudden development of profound hypotension (60/35 mmHg) and bradycardia with a minimum heart rate of 40 beats.min(-1). Initial resuscitative efforts included administration of intravascular fluid, hypertonic saline, atropine, adrenalin (more than 10 mg in divided doses) and noradrenalin. These measures restored the blood pressure to 80/45 with a HR of 98 beats.min(-1). Intraoperative placement of an intraventricular drain released cerebrospinal fluid under pressure with an initial intracranial pressure of 15 cm H(2)O. A combination of adrenalin, noradrenalin, dopamine and vasopressin infusions were required to restore the blood pressure to 130/65 mmHg after an additional two hours. All inotropic and vasopressor support was weaned off after the 14th hr (about two drug half-lives). The patient was awake and responsive the following day, with no obvious neurological consequences. No evidence of neurological injury, drug administration error or myocardial dysfunction was documented.

CONCLUSION

The episode of profound hypotension which occurred after initiating a labetolol infusion required maximal combined vasopressor therapy to restore the blood pressure suggesting that this patient demonstrated an extreme sensitivity to labetalol. Combination therapy with adrenergic and nonadrenergic agonists may be required for optimal treatment of profound hypotension associated with labetalol-induced vasoplegia.

Yeast-based functional genomics and proteomics technologies: the first 15 years and beyond

Yeast-based functional genomics and proteomics technologies developed over the past decade have contributed greatly to our understanding of bacterial, yeast, fly, worm, and human gene functions. In this review, we highlight some of these yeast-based functional genomic and proteomic technologies that are advancing the utility of yeast as a model organism in molecular biology and speculate on their future uses. Such technologies include use of the yeast deletion strain collection, large-scale determination of protein localization in vivo, synthetic genetic array analysis, variations of the yeast two-hybrid system, protein microarrays, and tandem affinity purification (TAP)-tagging approaches. The integration of these advances with established technologies is invaluable in the drive toward a comprehensive understanding of protein structure and function in the cellular milieu.

Hypertensive crisis: hypertensive emergencies and urgencies

Hypertensive crisis is a serious condition that is associated with end-organ damage or may result in end-organ damage if left untreated. Causes of acute rises in blood pressure include medications,noncompliance, and poorly controlled chronic hypertension. Treatment of a hypertensive crisis should be tailored to each individual based on the extent of end-organ injury and comorbid conditions. Prompt and rapid reduction of blood pressure under continuous surveillance is essential in patients who have acute end-organ damage.

Efficacy and safety of once- and twice-daily formulations of molsidomine in patients with stable angina pectoris: double-blind and open-label studies

Molsidomine, a sydnonimine acting as a heterocyclic direct nitric oxide donor, has been used for many years in several European countries for the treatment of patients with stable angina pectoris. The efficacy and tolerability of a novel once-daily 16-mg formulation of molsidomine (M16) were compared with those of the currently used twice-daily 8-mg molsidomine tablet (M8) in 666 patients. Study 1, a multicenter, randomized, double-blind, placebo-controlled, twin crossover study, involved 533 patients given acute and 2-week treatment with each drug formulation. Study 2, a multicenter, open-label, sequential, add-on trial, compared M16 and M8 in 133 patients. Drug effects on exercise capacity (study 1 only), frequency of anginal attacks and consumption of short-acting itroderivatives, and incidence of adverse events (AEs) were evaluated. Compared with placebo, M16 increased exercise capacity by 15% (P<.001) at the start of study 1 and by 13% (P<.001) after 2 weeks' treatment, and was not inferior to M8. In terms of anginal attack frequency and nitroderivative consumption, M16 was not inferior to M8 in either study. Moreover, compared with M8, M16 produced a statistically and clinically significant reduction in the incidence of anginal attacks in elderly (>/=75 y) but not in younger patients (<75 y) (study 2), nor in patients from study 1. No significant difference from M8 was found in either study in short-acting nitroderivative consumption. No tolerance to M8 or M16 was observed after 2-week treatment. No statistically significant differences in incidences of all AEs and drug-related AEs were observed between M16 and M8 in either study. The same held true for proportions of patients experiencing AEs and drug-related AEs on M16 vs M8: in study 1-14.3% and 11.8% for all AEs (P=.218), 6.9% and 5.4% for drug-related AEs (P=.280); in study 2-1.3% and 1.3% for all AEs, 0% and 1.3% for drug-related AEs (P>.10) in young patients; and in the elderly, 3.6% and 0% for drug-related AEs (P>.10). Only the proportion of elderly patients with all AEs was significantly higher with M16 than with M8: 14.5% vs 1.8% (P=.039). M16 once daily was effective and well tolerated in investigated patients with stable angina pectoris, particularly the elderly, affording 24 hours of therapeutic activity. M16 was not inferior to M8 given twice daily in terms of efficacy, safety profile, and tolerability.

A phase I study of hydralazine to demethylate and reactivate the expression of tumor suppressor genes

Background

The antihypertensive compound hydralazine is a known demethylating agent. This phase I study evaluated the tolerability and its effects upon DNA methylation and gene reactivation in patients with untreated cervical cancer.

Methods

Hydralazine was administered to cohorts of 4 patients at the following dose levels: I) 50 mg/day, II) 75 mg/day, III) 100 mg/day and IV) 150 mg/day. Tumor biopsies and peripheral blood samples were taken the day before and after treatment. The genes APC, MGMT; ER, GSTP1, DAPK, RARβ, FHIT and p16 were evaluated pre and post-treatment for DNA promoter methylation and gene expression by MSP (Methylation-Specific PCR) and RT-PCR respectively in each of the tumor samples. Methylation of the imprinted H19 gene and the "normally methylated" sequence clone 1.2 was also analyzed. Global DNA methylation was analyzed by capillary electrophoresis and cytosine extension assay. Toxicity was evaluated using the NCI Common Toxicity Criteria.

Results

Hydralazine was well tolerated. Toxicities were mild being the most common nausea, dizziness, fatigue, headache and palpitations. Overall, 70% of the pretreatment samples and all the patients had at least one methylated gene. Rates of demethylation at the different dose levels were as follows: 50 mg/day, 40%; 75 mg/day, 52%, 100 mg/day, 43%, and 150 mg/day, 32%. Gene expression analysis showed only 12 informative cases, of these 9 (75%) re-expressed the gene. There was neither change in the methylation status of H19 and clone 1.2 nor changes in global DNA methylation.

Conclusion

Hydralazine at doses between 50 and 150 mg/day is well tolerated and effective to demethylate and reactivate the expression of tumor suppressor genes without affecting global DNA methylation

Efficacy and safety of molsidomine once-a-day in patients with stable angina pectoris

BACKGROUND

The objective of this study was to compare the efficacy and tolerability of molsidomine prolonged-release 16 mg once-a-day (o.a.d.) with 8 mg twice-a-day (b.i.d.) and placebo in patients with stable angina pectoris.

METHODS

After a run-in placebo period of 7 days, the two formulations were compared acutely and then chronically (2 weeks) using cycloergometric tests and a randomized, multicenter, double-blind, double-dummy, crossover design in 533 patients. The quality of life was assessed using the frequency of anginal crises and nitrate sublingual tablets consumption.

RESULTS

Both formulations significantly improved exercise test parameters compared with placebo, being it after acute drug intake or after a 2-week treatment period and independently of spontaneous diurnal variation in exercise tolerance. Noninferiority of molsidomine 16 mg compared with 8 mg was demonstrated with a statistically significant superiority of the 16-mg formulation from 14 to 24 h postintake. Both treatments reduced incidence of anginal attacks and use of sublingual isosorbide dinitrate tablets. Tolerability of active drugs was satisfactory, the incidence of drug-related headache being not significantly different from placebo. Only hypotension was significantly more frequent with molsidomine 16 mg than with placebo, pretrial diastolic blood pressure being significantly lower in these patients than in those who did not develop hypotension during the study.

CONCLUSIONS

Both molsidomine formulations were effective in controlling patients' angina, did not induce any habituation and were well tolerated. However, the once-daily 16-mg formulation tended to provide better 24-h protection against myocardial ischemia than the 8-mg b.i.d. formulation.

Nesiritide for the treatment of congestive heart failure

Nesiritide (Natrecor) is a recombinant form of the human B-type natriuretic peptide (BNP) that has been shown, through several studies, to have beneficial natriuretic, diuretic and vasodilatory effects in the treatment of congestive heart failure (CHF). Nesiritide mimics the actions of endogenous BNP by binding to and stimulating receptors in the heart, kidney and vasculature. Nesiritide functions as both a potent venous and arterial vasodilator and has been shown to improve cardiac haemodynamics more rapidly and to a greater extent than intravenous nitroglycerin, as well as having fewer side effects. When compared in an open-label trial, nesiritide has also been shown to be less proarrhythmic than dobutamine. The major adverse effect of nesiritide, as with other vasodilators, is symptomatic hypotension, which occurred infrequently in clinical trials. Overall, nesiritide represents an effective and safe therapeutic option for the treatment of decompensated CHF.

Sublingual nitroglycerin versus intravenous ritodrine as tocolytic for external cephalic version: a double-blinded randomized trial

OBJECTIVE

The purpose of this study was to compare the efficacy of sublingual nitroglycerin with that of intravenous ritodrine as a tocolytic agent for external cephalic version in nulliparous women.

STUDY DESIGN

We performed a double-blinded, randomized trial. Nulliparous patients, between 36 and 40 weeks of gestation, were assigned randomly to receive either (1) an intravenous infusion of ritodrine (111 microg/min) for 20 minutes, followed by two puffs of sublingual placebo or (2) an intravenous infusion of sodium chloride 0.9% (placebo) for 20 minutes, followed by two puffs of sublingual 0.4 mg of nitroglycerin. Three minutes after the administration of the sublingual spray, an external cephalic version was attempted. The rate of successful external cephalic version and side effects was compared between groups.

RESULTS

Of 74 randomly assigned patients, 38 patients received intravenous ritodrine, and 36 patients received sublingual nitroglycerin. Although not statistically significant, the rate of the successful external cephalic version was higher in the ritodrine group compared with the nitroglycerin group (45% vs 25%, P =.075). The rate of headaches was higher in patients who received nitroglycerin (28% vs 8%, P =.02). Mean blood pressure and maternal heart rate were lower in the nitroglycerin group 10 minutes after the administration of the medication. However, there was no significant difference in the rate of palpitations, hypotension, or fetal bradycardia between the two groups.

CONCLUSION

When compared with intravenous ritodrine, sublingual nitroglycerin was associated with a higher rate of headache, lower blood pressure, and a trend toward a lower rate of successful external cephalic version.

The pharmacokinetics of glyceryl trinitrate with the use of the in vitro term human placental perfusion setup

OBJECTIVE

The purpose of this study was to determine the pharmacokinetics of glyceryl trinitrate across the in vitro term human perfused placenta.

STUDY DESIGN

Peripheral placental lobules (n = 6) were dually perfused. The maternal side was perfused with glyceryl trinitrate (100 nmol/L) for 90 minutes. Serial samples from the fetal venous and maternal venous catheters were collected and assayed for glyceryl trinitrate and its vasoactive metabolites (1,2- and 1,3-glyceryl dinitrate) with gas chromatography. Fetal arterial perfusion pressure was continuously measured throughout. Data are expressed as the mean +/- SEM, with 1-way analysis of variance followed by a Newman-Keuls post-hoc test (P <.05).

RESULTS

The mean steady-state fetal venous:maternal side ratio of glyceryl trinitrate concentration was 18.5% +/- 3.7%. The 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate levels in the fetal venous samples and maternal venous samples were less than the lower end of the sensitivity range of the assay (<5 nmol/L). Fetal arterial perfusion pressure did not change with glyceryl trinitrate administration.

CONCLUSION

The glyceryl trinitrate in the fetal venous sample was approximately 18.5% of the glyceryl trinitrate in the maternal side in this preparation. The presence of glyceryl dinitrates in the maternal venous samples and the fetal venous samples indicates the capacity for placental biotransformation of glyceryl trinitrate. The data demonstrate that glyceryl trinitrate, at a tocolytic concentration, has the ability to cross the placenta but was not found to affect fetal arterial perfusion pressure.

Nesiritide: a new drug for the treatment of decompensated heart failure

Nesiritide, a recombinant human B-type natriuretic peptide, is the first in a new drug class for the treatment of decompensated heart failure. The drug binds to receptors in the vasculature, kidney, adrenal gland, and brain, and overcomes resistance to endogenous BNP present in patients with CHF. Nesiritide administration leads to a rapid and balanced vasodilatory effect, which results in a significant decrease in right and left ventricular filling pressures and systemic vascular resistance and at the same time in an increase in stroke volume and cardiac output without a change in heart rate. These early hemodynamic changes result in a rapid improvement in symptoms of heart failure. In addition, nesiritide lowers aldosterone, catecholamines, and endothelin-1 levels and its effect on the kidney leads to an increased natriuresis and diuresis without effect on serum potassium or renal function. Prior to its approval for clinical use, nesiritide was studied in 10 different clinical trials involving 941 patients with moderate and severe CHF, including elderly patients, patients with both systolic and diastolic dysfunction, and patients with arrhythmias, renal insufficiency, and acute ischemic syndrome. In comparative studies with available vasoactive therapies frequently used for treatment of patients with decompensated heart failure, nesiritide was proven comparable in efficacy to inotropic drugs such as dobutamine, but superior in safety. In a recent study, nesiritide was found to be more effective and better tolerated than the vasodilator, nitroglycerin. The most common side effects expected with the use of nesiritide are headaches and decrease in blood pressure. At the recommended dose of nesiritide, headache was reported during the first 24 hours of treatment in 8% of patients and symptomatic hypotension in 4% of patients, compared to 20% and 5% in nitroglycerin-treated patients.

The effect of antihypertensive drugs on the fetus

A critical review of the literature on the effects of antihypertensive drugs on the fetus in pregnant women is presented. The survey covers the alpha-adrenergic receptor agonists, beta-blockers including topical eye medications, alpha-beta blockers, calcium antagonists, diuretics, and angiotensin-converting enzyme (ACE) inhibitors. The lack of data on angiotensin II receptor blockers is noted although effects are considered to be similar to those reported with ACE inhibitors and therefore to be avoided. Analysis of the literature underscores that some antihypertensive drugs can be used safely at certain stages of pregnancy, while others are suspect and to be avoided at all costs. The lack of placebo-controlled studies on the treatment of severe hypertension in pregnancy due to ethical considerations is discussed against the background of the pressing need to treat these women despite the possible deleterious effects of antihypertensive drugs.

Calcium channel blockers in the management of preterm labor and hypertension in pregnancy

Calcium channel blockers (CCBs) have the ability to inhibit contractility in smooth muscle cells. CCBs have an already established role in the treatment of non-pregnant hypertension and angina pectoris. Some epidemiological studies found an association between the use of CCBs and an increase in cardiovascular mortality, malignancy, and gastrointestinal bleeding. More recent studies with many more patients and a longer follow-up did not find these associations. In obstetrics CCBs have become increasingly popular for the management of preterm labor and pregnancy-induced hypertensive disorders. Meta-analysis shows that use of nifedipine in comparison with betamimetics is associated with a more frequent successful prolongation of pregnancy in case of preterm labor, resulting in significantly fewer admissions of newborns to the neonatal intensive care unit (NICU), and is associated with a lower incidence of respiratory distress syndrome. No adverse fetal side effects in humans have been reported with the use of nifedipine for obstetric indications. Nifedipine is an effective and safe drug to use when tocolytic therapy is indicated for preterm labor. In preeclampsia nifedipine effectively lowers blood pressure and can be a good alternative for (di) hydralazine.

Evaluation of human intestinal absorption data and subsequent derivation of a quantitative structure–activity relationship (QSAR) with the Abraham descriptors

The human intestinal absorption of 241 drugs was evaluated. Three main methods were used to determine the human intestinal absorption: bioavailability, percentage of urinary excretion of drug-related material following oral administration, and the ratio of cumulative urinary excretion of drug-related material following oral and intravenous administration. The general solvation equation developed by Abraham's group was used to model the human intestinal absorption data of 169 drugs we considered to have reliable data. The model contains five Abraham descriptors calculated by the ABSOLV program. The results show that Abraham descriptors can successfully predict human intestinal absorption if the human absorption data is carefully classified based on solubility and administration dose to humans.

Antiproliferative effects of trapidil in vascular smooth muscle cells are associated by inhibition of MAPK and P34(cdc2) activity

Trapidil (Tra) is a potent coronary vasodilator. Recent studies have shown that Tra possesses antiproliferative activity in glioma cells and vascular smooth muscle cells (VSMCs). These studies were undertaken to determine the effects of Tra on the cell cycle of cultured rat VSMCs, in particular, the effects on two key enzymes responsible for cell-cycle control in cultured rat VSMCs. VSMCs were synchronized by serum deprivation and then stimulated to enter the cell cycle by serum refeeding; the cell-cycle distribution was subsequently measured by flow cytometry, and VSMCs pretreated with 5, 50, and 500 microM Tra showed a decrease in S-phase cell-cycle distribution, 13.1, 18.7, and 58.6%, respectively. In addition, the mitotic activity (S + G2/M) decreased 12.9, 18.7, and 49.6%, respectively after Tra treatment. The protein expression of p34cdc2 was determined by Western blot analysis, and Tra treatment did not affect its expression even at 500 microM. Mitogen-activated protein kinase (MAPK) activity and p34cdc2 kinase activity were assayed by phosphorylation of their specific substrates, myelin basic protein (MBP) and histone H1, after immunoprecipitation. Exposure of VSMCs to Tra resulted in a significant decrease in serum-stimulated MAPK and p34cdc2 activity. The inhibitory rates of 50 and 500 microM Tra on MAPK activity were 59.2 and 80.9%, respectively. Tra concentrations of 5, 50, and 500 microM inhibited p34cdc2 activity by 16.4, 22.6, and 40.8%, respectively. Furthermore, 500 microM Tra inhibited the basal kinase activities of MAPK and p34cdc2 in the cells that were not serum stimulated. These findings demonstrate that Tra significantly decreases the mitotic activity of cultured VSMCs, and that this effect is associated with the inhibitory role of Tra on the kinase activities of MAPK and p34cdc2.

Intraportal administration of glyceryl trinitrate or nitroprusside exerts more systemic than intrahepatic effects in anaesthetised cirrhotic rats

BACKGROUND/AIMS

Increased intrahepatic vascular tone can be pharmacologically manipulated in isolated cirrhotic livers. Intrahepatic endothelial dysfunction may lead to a decreased production of the potent endogenous vasodilator nitric oxide in cirrhotic livers. The aims of the study were to determine whether portal pressure can be lowered in vivo by injecting nitric oxide donors glyceryl trinitrate or nitroprusside directly in the portal vein and whether this is related to a decrease in intrahepatic resistance.

METHODS

In anaesthetised CCl4 cirrhotic rats, intraportal doses of glyceryl trinitrate 0.5, 1 or 5 microg/kg/ min or nitroprusside 1, 5 or 10 microg/kg/min did not decrease portal pressure but only arterial pressure. Systemic and splanchnic haemodynamics were measured before and during 15 min intraportal infusion of glyceryl trinitrate 10 microg/kg/min or nitroprusside 20 microg/kg/min.

RESULTS

Glyceryl trinitrate decreased portal pressure from 14.0+/-1.1 to 11.8+/-1.4 mm Hg, splanchnic perfusion pressure from 102+/-10 to 74+/-5 mm Hg and portal sinusoidal flow from 2.11+/-0.38 to 1.70+/-0.35 ml/min/g liver (all p<0.05). Nitroprusside did not decrease portal pressure significantly but led to a reduction of the splanchnic perfusion pressure (104+/-9 to 66+/-7 mm Hg) and the portal sinusoidal flow (2.39+/-0.50 to 1.77+/-0.31 ml/min/g liver; all p<0.05). Portal sinusoidal resistance was not altered by either drug.

CONCLUSIONS

Intraportal infusion of nitric oxide donors decreased arterial pressure more than portal pressure. Portal sinusoidal resistance remained unaffected, but the liver parenchyma became less perfused with high doses. The systemic effects of nitric oxide donating drugs prevailed.