Gender-specific effects on verapamil pharmacokinetics and pharmacodynamics in humans

The relationship between gender and pharmacology

The part of sexuality in pharmacology research was not acknowledged, and it was not thought-out to be a determinant that could impact strength and disease. For decades research has mainly contained male, women and animals, leading to a lack of news about syndromes in females. Still, it is critical to guarantee equal likeness so that determine the security, influence, and resistance of healing agents for all individuals. The underrepresentation of female models in preclinical studies over various decades has surpassed to disparities in the understanding, disease, and treatment of ailments 'tween genders. The closeness of sexuality bias has happened recognized as a contributing determinant to the restricted interpretation and replicability of preclinical research. Many demands operation have stressed the significance of including sexuality as a organic changeable, and this view is acquire growing support. Regardless of important progress in incorporating more female models into preclinical studies, differences prevail contemporary. The current review focuses on the part of sexuality and common in biomedical research and, therefore, their potential function in pharmacology and analyze the potential risks guide.

Evaluating gender effect in the generic bioequivalence studies by physiologically based pharmacokinetic modeling - A case study of dextromethorphan modified release tablets

The United States Food and Drug Administration guidelines for the bioequivalence (BE) testing of the generic drug products suggests that there should be an equal proportion of male and female population in the BE study. Despite this requirement, many generic drug companies do not maintain the suggested proportion of female population in their studies. Several socio-economic and cultural factors lead to lower participation of the females in the BE studies. More recently, the regulatory agencies across the globe are requesting the generic drug companies to demonstrate the performance of their drug products in the under-represented sex via additional studies. In this work, we describe the case of Dextromethorphan modified release tablets where the gender effect on the product performance was evaluated by physiologically based pharmacokinetic (PBPK) modeling approach. We have compared the drug product's performance by population simulations considering four different scenarios. The data from all-male population (from in house Pharmacokinetic [PK] BE studies) was considered as a reference and other scenarios were compared against the all-male population data. In the first scenario, we made a comparison between all-male (100% male) vs all-female (100% female) population. Second scenario was as per agency's requirements-equal proportion of male and female in the BE study. As an extreme scenario, 100% male vs 30:70 male:female was considered (higher females than males in the BE studies). Finally, as a more realistic scenario, 100% male versus 70:30 male:female was considered (lower females than males in the BE studies). Population PK followed by virtual BE was employed to demonstrate the similarity/differences in the drug product performance between the sexes. This approach can be potentially utilized to seek BE study waivers thus saving cost and accelerating the entry of the generic products to the market.

Gender Medicine and Pharmacology

Gender-specific medicine consists of a transversal methodological approach that aims to study the influence of sex and gender on diseases [...].

Evaluation of Sex Differences in Preclinical Pharmacology Research: How Far Is Left to Go?

Until the last quarter of the 20th century, sex was not recognized as a variable in health research, nor was it believed to be a factor that could affect health and illness. Researchers preferred studying male models for a variety of reasons, such as simplicity, lower costs, hormone confounding effects, and fear of liability from perinatal exposure in case of pregnancy. Equitable representation is imperative for determining the safety, effectiveness, and tolerance of therapeutic agents for all consumers. Decades of female models' underrepresentation in preclinical studies has resulted in inequality in the understanding, diagnosis, and treatment of disease between the sexes. Sex bias has been highlighted as one of the contributing factors to the poor translation and replicability of preclinical research. There have been multiple calls for action, and the inclusion of sex as a biological variable is increasingly supported. However, although there has been substantial progress in the efforts to include more female models in preclinical studies, disparities today remain. In the present review, we consider the current standard practice of the preclinical research setting, why the sex bias exists, why there is the need to include female models, and what risks may arise from continuing this exclusion from experimental design.

Regulation of ABC transporters by sex steroids may explain differences in drug resistance between sexes

Drug efficacy is dependent on the pharmacokinetics and pharmacodynamics of therapeutic agents. Tight junctions, detoxification enzymes, and drug transporters, due to their localization on epithelial barriers, modulate the absorption, distribution, and the elimination of a drug. The epithelial barriers which control the pharmacokinetic processes are sex steroid hormone targets, and in this way, sex hormones may also control the drug transport across these barriers. Thus, sex steroids contribute to sex differences in drug resistance and have a relevant impact on the sex-related efficacy of many therapeutic drugs. As a consequence, for the further development and optimization of therapeutic strategies, the sex of the individuals must be taken into consideration. Here, we gather and discuss the evidence about the regulation of ATP-binding cassette transporters by sex steroids, and we also describe the signaling pathways by which sex steroids modulate ATP-binding cassette transporters expression, with a focus in the most important ATP-binding cassette transporters involved in multidrug resistance.

Sex and gender differences in the treatment of arterial hypertension

INTRODUCTION

Arterial hypertension represents the leading modifiable risk factor for all-cause death and early development of cardiovascular disease in women. Current clinical guidelines for the treatment of hypertension noted that women respond to antihypertensive drugs similarly to men and, therefore, treatment recommendations remain the same for both sexes. However, clinical evidence suggests the existence of sex- and gender-related differences (SGRD) in the prevalence, pathophysiology, pharmacodynamics (efficacy and safety) and pharmacokinetics of antihypertensive drugs.

AREAS COVERED

This review summarizes SGRD in the prevalence of hypertension, hypertension-mediated organ damage and blood pressure control, prescription patterns, and pharmacokinetics/ pharmacodynamics and doses of antihypertensive drugs.

EXPERT OPINION

There is limited information on SGRD in antihypertensive drug efficacy because of the underrepresentation of women in randomized clinical trials and, more important, because few trials reported results stratified by sex or performed sex-specific analyses. However, there are SGRD in hypertension-mediated organ damage, drug pharmacokinetics and, particularly, in drug safety. Prospective trials specifically designed to better understand the basis for SGRD in the pathophysiology of hypertension and in the efficacy and safety of antihypertensive drugs are needed to achieve a more personalized treatment of hypertension and hypertension-mediated organ damage in women.

Hypertension in Women: The Current Understanding and Future Goals

Hypertension is one of the major contributing risk factor of cardiovascular diseases. Despite enormous advances in the preventive cardiology, hypertension remains the leading cause of death and disability in women. The article aims to focus on the gender specific differences in hypertension, and existing gaps in the current understanding of high blood pressure (BP) in women. Apart from epidemiological differences, hypertension in men and women has distinct pathophysiological mechanisms, impact on cardiovascular system, awareness and control. Prevalence of hypertension is higher in men than women till menopause; following this the prevalence rises steeply in women, and exceeds that of men above 75 years of age. Women with their estrogenic environment are relatively protected from high BP as their hormonal/chromosomal profile govern expression of alternate renin angiotensin axis (RAS) pathway and anti-inflammatory, vasodilatory, anti-proliferative immune cells whereas in males, classical RAS driven inflammatory, pro-hypertensive and proliferative milieu confers higher risk of hypertension. Thus, immunotherapy can have a potential therapeutic role in the treatment of hypertension in future. Cardiovascular consequences of high BP are worse in women than men in majority of trials. Women are now getting more aware of hypertension but the control of BP still remains poorer than men, especially in older age group. There are some noteworthy pharmacokinetic and pharmacogenomics gender differences in response to various antihypertensive drugs, which can be taken into consideration while choosing a particular class of drugs in female population. Standard treatment guidelines recommend same BP targets and management strategies in both the genders, but the trials so far have not been designed in a way to draw women specific conclusions on optimal cut-offs for diagnosis and treatment of BP due to under representation of women in majority of trials. More women centered analysis in future hypertension research projects can provide better scientific insights in various clinical aspects of hypertension.

Sex-Related Differences in Pharmacological Response to CNS Drugs: A Narrative Review

In the last decades, both animal and human studies have neglected female subjects with the aim of evading a theorized intricacy of feminine hormonal status. However, clinical experience proves that pharmacological response may vary between the two sexes since pathophysiological dissimilarities between men and women significantly influence the pharmacokinetics and pharmacodynamics of drugs. Sex-related differences in central nervous system (CNS) medication are particularly challenging to assess due to the complexity of disease manifestation, drugs’ intricate mechanisms of action, and lack of trustworthy means of evaluating the clinical response to medication. Although many studies showed contrary results, it appears to be a general tendency towards a certain sex-related difference in each pharmacological class. Broadly, opioids seem to produce better analgesia in women especially when they are administered for a prolonged period of time. On the other hand, respiratory and gastrointestinal adverse drug reactions (ADRs) following morphine therapy are more prevalent among female patients. Regarding antidepressants, studies suggest that males might respond better to tricyclic antidepressants (TCAs), whereas females prefer selective serotonin reuptake inhibitors (SSRI), probably due to their tolerance to particular ADRs. In general, studies missed spotting any significant sex-related differences in the therapeutic effect of antiepileptic drugs (AED), but ADRs have sex variations in conjunction with sex hormones’ metabolism. On the subject of antipsychotic therapy, women appear to have a superior response to this pharmacological class, although there are also studies claiming the opposite. However, it seems that reported sex-related differences regarding ADRs are steadier: women are more at risk of developing various side effects, such as metabolic dysfunctions, cardiovascular disorders, and hyperprolactinemia. Taking all of the above into account, it seems that response to CNS drugs might be occasionally influenced by sex as a biological variable. Nonetheless, although for each pharmacological class, studies generally converge to a certain pattern, opposite outcomes are standing in the way of a clear consensus. Hence, the fact that so many studies are yielding conflicting results emphasizes once again the need to address sex-related differences in pharmacological response to drugs.

A framework for developing sex-specific engineered heart models

The convergence of tissue engineering and patient-specific stem cell biology has enabled the engineering of in vitro tissue models that allow the study of patient-tailored treatment modalities. However, sex-related disparities in health and disease, from systemic hormonal influences to cellular-level differences, are often overlooked in stem cell biology, tissue engineering and preclinical screening. The cardiovascular system, in particular, shows considerable sex-related differences, which need to be considered in cardiac tissue engineering. In this Review, we analyse sex-related properties of the heart muscle in the context of health and disease, and discuss a framework for including sex-based differences in human cardiac tissue engineering. We highlight how sex-based features can be implemented at the cellular and tissue levels, and how sex-specific cardiac models could advance the study of cardiovascular diseases. Finally, we define design criteria for sex-specific cardiac tissue engineering and provide an outlook to future research possibilities beyond the cardiovascular system.

Let's talk about sex: Differences in drug therapy in males and females

Professor Henry Higgins in My Fair Lady said, 'Why can't a woman be more like a man?' Perhaps unintended, such narration extends to the reality of current drug development. A clear sex-gap exists in pharmaceutical research spanning from preclinical studies, clinical trials to post-marketing surveillance with a bias towards males. Consequently, women experience adverse drug reactions from approved drug products more often than men. Distinct differences in pharmaceutical response across drug classes and the lack of understanding of disease pathophysiology also exists between the sexes, often leading to suboptimal drug therapy in women. This review explores the influence of sex as a biological variable in drug delivery, pharmacokinetic response and overall efficacy in the context of pharmaceutical research and practice in the clinic. Prospective recommendations are provided to guide researchers towards the consideration of sex differences in methodologies and analyses. The promotion of disaggregating data according to sex to strengthen scientific rigour, encouraging innovation through the personalisation of medicines and adopting machine learning algorithms is vital for optimised drug development in the sexes and population health equity.

The role of sex, age and genetic polymorphisms of CYP enzymes on the pharmacokinetics of anticholinergic drugs

There is evidence that use of drugs with anticholinergic properties increases the risk of cognitive impairment, and increased exposure to these drugs potentiates this risk. Anticholinergic drugs are commonly used even with associated risk of adverse events. Aging, sex, and genetic polymorphisms of cytochrome P450 (CYP) enzymes are associated with alterations in pharmacokinetic processes, which increase drug exposure and may further increase the risk of adverse drug events. Due to the increasing burden of cognitive impairment in our aging population and the future of personalized medicine, the objective of this review was to provide a critical clinical perspective on age, sex, and CYP genetic polymorphisms and their role in the metabolism and exposure to anticholinergic drugs. Age-related changes that may increase anticholinergic drug exposure include pseudocapillarization of liver sinusoidal endothelial cells, an approximate 3.5% decline in CYP content for each decade of life, and a reduction in kidney function. Sex-related differences that may be influenced by anticholinergic drug exposure include women having delayed gastric and colonic emptying, higher gastric pH, reduced catechol-O-methyl transferase activity, reduced glucuronidation, and reduced renal clearance and men having larger stomachs which may affect medication absorption. The overlay of poor metabolism phenotypes for CYP2D6 and CYP2C19 may further modify anticholinergic drug exposure in a significant proportion of the population. These factors help explain findings of clinical trials that show older adults and specifically older women achieve higher plasma concentrations of anticholinergic drugs and that poor metabolizers of CYP2D6 experience increased drug exposure. Despite this knowledge neither age, sex nor CYP phenotype are routinely considered when making decisions about the use or dosing of anticholinergic medications. Future study of anticholinergic medication needs to account for age, sex and CYP polymorphisms so that we may better approach personalized medicine for optimal outcomes and avoidance of medication-related cognitive impairment.

Sex-related differences in the pharmacological treatment of heart failure

Heart failure (HF) represents a leading cause of morbidity and mortality. However, HF trials highlighted many differences between men and women with HF. Thus, women represent approximately a quarter of people with HF with reduced ejection fraction (HFrEF), while they account for over half of those with HF with preserved EF (HFpEF). There are also sex-related differences (SRDs) in the pharmacokinetics, pharmacodynamics and safety profile of some guideline-recommended drugs for the treatment of HF. As compared with men, women with HFrEF are less often treated with guideline-recommended HF drugs, experience more frequent and severe adverse reactions when these drugs are prescribed at the same doses in both sexes, and recent evidence suggests that women might need lower doses than men, bringing into question which are the optimal doses of HF drugs in women and men separately. However, information on SRDs in drug efficacy and safety in patients with HFrEF is very limited due to the underrepresentation of women and the lack of sex-specific evaluations of drug efficacy and safety in HF clinical trials. As a consequence, current clinical guidelines do not provide sex-specific recommendations, even when significant differences exist, at least, in drug safety. The aim of this article is to review the SRDs in the pharmacokinetics, efficacy and safety of guideline-recommended HF drugs and to identify emerging areas of research to improve our understanding of the SRDs, because a better understanding of these differences is the first step to achieve a personalized treatment of HF in women and men.

Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review

The absorption of oral drugs is frequently plagued by significant variability with potentially serious therapeutic consequences. The source of variability can be traced back to interindividual variability in physiology, differences in special populations (age- and disease-dependent), drug and formulation properties, or food-drug interactions. Clinical evidence for the impact of some of these factors on drug pharmacokinetic variability is mounting: e.g. gastric pH and emptying time, small intestinal fluid properties, differences in pediatrics and the elderly, and surgical changes in gastrointestinal anatomy. However, the link of colonic factors variability (transit time, fluid composition, microbiome), sex differences (male vs. female) and gut-related diseases (chronic constipation, anorexia and cachexia) to drug absorption variability has not been firmly established yet. At the same time, a way to decrease oral drug pharmacokinetic variability is provided by the pharmaceutical industry: clinical evidence suggests that formulation approaches employed during drug development can decrease the variability in oral exposure. This review outlines the main drivers of oral drug exposure variability and potential approaches to overcome them, while highlighting existing knowledge gaps and guiding future studies in this area.

Drug-induced peripheral oedema: An aetiology-based review

Many drugs are responsible, through different mechanisms, for peripheral oedema. Severity is highly variable, ranging from slight oedema of the lower limbs to anasarca pictures as in the capillary leak syndrome. Although most often noninflammatory and bilateral, some drugs are associated with peripheral oedema that is readily erythematous (eg, pemetrexed) or unilateral (eg, sirolimus). Thus, drug-induced peripheral oedema is underrecognized and misdiagnosed, frequently leading to a prescribing cascade. Four main mechanisms are involved, namely precapillary arteriolar vasodilation (vasodilatory oedema), sodium/water retention (renal oedema), lymphatic insufficiency (lymphedema) and increased capillary permeability (permeability oedema). The underlying mechanism has significant impact on treatment efficacy. The purpose of this review is to provide a comprehensive analysis of the main causative drugs by illustrating each pathophysiological mechanism and their management through an example of a drug.

Extracorporeal treatment for calcium channel blocker poisoning: systematic review and recommendations from the EXTRIP workgroup

BACKGROUND

Calcium channel blockers (CCBs) are commonly used to treat conditions such as arterial hypertension and supraventricular dysrhythmias. Poisoning from these drugs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in the management of CCB poisoning.

METHODS

We conducted systematic reviews of the literature, screened studies, extracted data, summarized findings, and formulated recommendations following published EXTRIP methods.

RESULTS

A total of 83 publications (6 in vitro and 1 animal experiments, 55 case reports or case series, 19 pharmacokinetic studies, 1 cohort study and 1 systematic review) met inclusion criteria regarding the effect of ECTR. Toxicokinetic or pharmacokinetic data were available on 210 patients (including 32 for amlodipine, 20 for diltiazem, and 52 for verapamil). Regardless of the ECTR used, amlodipine, bepridil, diltiazem, felodipine, isradipine, mibefradil, nifedipine, nisoldipine, and verapamil were considered not dialyzable, with variable levels of evidence, while no dialyzability grading was possible for nicardipine and nitrendipine. Data were available for clinical analysis on 78 CCB poisoned patients (including 32 patients for amlodipine, 16 for diltiazem, and 23 for verapamil). Standard care (including high dose insulin euglycemic therapy) was not systematically administered. Clinical data did not suggest an improvement in outcomes with ECTR. Consequently, the EXTRIP workgroup recommends against using ECTR in addition to standard care for patients severely poisoned with either amlodipine, diltiazem or verapamil (strong recommendations, very low quality of the evidence (1D)). There were insufficient clinical data to draft recommendation for other CCBs, although the workgroup acknowledged the low dialyzability from, and lack of biological plausibility for, ECTR.

CONCLUSIONS

Both dialyzability and clinical data do not support a clinical benefit from ECTRs for CCB poisoning. The EXTRIP workgroup recommends against using extracorporeal methods to enhance the elimination of amlodipine, diltiazem, and verapamil in patients with severe poisoning.

Brief Report: Sex Differences in Outcomes for Individuals Presenting for Third-Line Antiretroviral Therapy

BACKGROUND

Sex differences in studies of antiretroviral (ART) drug exposure and treatment outcomes support the hypothesis that some ART combinations may not be well tolerated in women. We evaluated disparities in outcomes between men and women participating in ACTG A5288, an interventional strategy trial for individuals failing a protease inhibitor-based second-line ART regimen in low- and middle-income countries.

METHODS

Participants were assigned to one of 4 cohorts (A-D) based on resistance profiles and ART history. Cohort A had no lopinavir/ritonavir (LPV/r) resistance and stayed on their second-line regimen, and cohorts B, C, and D had increasing resistance and accessed novel ART regimens. In this secondary analysis, we evaluated sex differences in the primary endpoint, HIV-1 RNA ≤200 copies/mL at week 48; confirmed virologic failure ≥1000 copies/mL (VF); and clinical outcomes and adverse events (intent-to-treat).

RESULTS

Women made up 258/545 (47%) of the study population. More women than men were assigned to cohort A. Median follow-up was 72 weeks. Fewer women than men had HIV-1 RNA ≤200 copies/mL at week 48: 39% vs. 49% in cohort A and 83% vs. 89% in cohorts B, C, and D combined. More women experienced VF, grade ≥3 signs and symptoms, but similar grade ≥3 diagnoses or laboratory abnormalities.

CONCLUSIONS

More women than men entered the study with a resistance profile suggesting that their second-line regimen could have been effective in maintaining virologic suppression. The more frequent occurrence of grade ≥3 signs and symptoms in women suggests that tolerability issues were under recognized in women on protease inhibitor-based therapy.

Optimized Trace Analysis of Verapamil in Biological Fluids Using Solvent Bar Micro Extraction Technique Coupled with HPLC-UV Detection

Introduction:

Verapamil (Verap) is an antidysrhythmic agent and a calcium channel blocker, indicated for angina, hypertension, supraventricular arrhythmias, and migraine.

Objective:

Drug monitoring plays a critical role in patient survival. In order to prevent the onset of drug toxicity, trace levels of this drug should be determined.

Methods:

For this reason, solvent bar microextraction technique coupled with high-performance liquid chromatography was implemented.

Results:

Under optimum condition, verapamil was micro-extracted from a donor solution (pH=11) to an acceptor solution (pH=3.2). It was transferred through n-octanol as the organic solvent, which was impregnated in the pores of the hollow fiber. Salt addition (30%) had the major effect on the efficiency of the method. Interaction of time (65 min), temperature (25°C), and stirring rate (818 rpm) had a significant effect too. It all resulted in a limit of detection and quantification of 15 ng mL-1 and 50 ng mL-1, respectively. The relative standard deviations of analysis were 4.9% within a day (n=3) and 5.7% between days (n=9). The calibration curves represented good linearity for urine and plasma samples with coefficient estimations higher than 0.99 with a linearity range of 50-5000 ng mL-1. The relative standard deviation for intra- (n=3) and inter-(n=9) day was 4.2% and 5.7%, respectively.

Conclusion:

It could be concluded that the application of this method for dose monitoring can be done at hospital and healthcare facilities.

Gender Differences in Cardiovascular Pharmacotherapy-the Example of Hypertension: A Mini Review

Cardiovascular disease (CVD) is the leading cause of mortality worldwide in both sexes. Despite considerable progress in better understanding the patterns of disease in women, they are still often undertreated and benefit less from evidence-based treatment. Hypertension is a key contributor to CVD and is also one of the most potent risk factors for heart failure in women. Even with the wide variety of available drugs, blood pressure control is globally suboptimal. Current guidelines do not suggest differential treatment of hypertension for women; however, a growing body of research suggests gender dimorphism in the pathophysiology of hypertension and pharmacological response to cardiovascular drugs. The clinical relevance of theses sex-divergent effects of drugs is still under investigation. Owing to the exponential relationship between blood pressure and cardiovascular mortality, even a modest decrease in blood pressure or therapeutic adhesion could be clinically \relevant. In this review, we explore the known pharmacological and pharmacokinetic sex differences with special attention to the main classes of antihypertensive treatment. Current data shows frequently higher drug exposures in women and more frequent adverse drug reactions in all antihypertensive drug groups. As far as cardiovascular prevention is concerned, sex-specific data is often lacking in clinical trials, highlighting the necessity to further study CVD and their treatment in both men and women.

Verapamil and Alzheimer's Disease: Past, Present, and Future

Verapamil is a phenylalkylamine class calcium channel blocker that for half a century has been used for the treatment of cardiovascular diseases. Nowadays, verapamil is also considered as a drug option for the treatment of several neurological and psychiatric disorders, such as cluster headache, bipolar disorders, epilepsy, and neurodegenerative diseases. Here, we review insights into the potential preventive and therapeutic role of verapamil on Alzheimer’s disease (AD) based on limited experimental and clinical data. Pharmacological studies have shown that verapamil has a wide therapeutic spectrum, including antihypertensive, anti-inflammatory, and antioxidative effects, regulation of the blood-brain barrier function, due to its effect on P-glycoprotein, as well as adjustment of cellular calcium homeostasis, which may result in the delay of AD onset or ameliorate the symptoms of patients. However, the majority of the AD individuals are on polypharmacotherapy, and the interactions between verapamil and other drugs need to be considered. Therefore, for an appropriate and successful AD treatment, a personalized approach is more than necessary. A well-known narrow pharmacological window of verapamil efficacy may hinder this approach. It is therefore important to note that the verapamil efficacy may be conditioned by different factors. The onset, grade, and brain distribution of AD pathological hallmarks, the time-sequential appearances of AD-related cognitive and behavioral dysfunction, the chronobiologic and gender impact on calcium homeostasis and AD pathogenesis may somehow be influencing that success. In the future, such insights will be crucial for testing the validity of verapamil treatment on animal models of AD and clinical approaches.

Sex and gender differences in polypharmacy in persons with dementia: A scoping review

Purpose:

To date, research studies in most disciplines have not made sex-based analysis a priority despite increasing evidence of its importance. We now understand that both sex and gender impact medication prescribing, use, and effect. This is particularly true for older adults with dementia who have alterations in drug metabolism, drug response, and the permeability of the blood–brain barrier. To better understand the influence of sex and gender on drug use in older adults with dementia, we conducted a scoping review.

Methods:

This scoping review systematically searched the Medline, Embase, Web of Science, CINAHL, and ProQuest databases to find published reports on polypharmacy in populations of older adults with dementia that included a sex- or gender-based analysis.

Results:

A total of 12 published reports were identified. Findings were cohort studies and case-control trials that commented on sex-related differences in medication use as a secondary analysis to the studies’ primary objective. These studies showed that community-dwelling women received more potentially inappropriate medications and more psychotropic medications, while nursing home dwelling men received more potentially inappropriate medications, cholinesterase inhibitors, and antipsychotics. None of the identified studies explicitly examined gender-related differences in medication use.

Conclusion:

This scoping review supports that there is inadequate understanding of both sex and gender differences in drug use in older men and women with dementia. To tailor medication-specific interventions to improve drug therapy for older adults with dementia, it is important that future work includes sex- or gender-based analysis of drug use.

Challenges and innovations of drug delivery in older age

Both drug delivery performance and various age-related physical, mental and physiological changes can affect drug effectiveness and safety in elderly patients. The many drug delivery systems developed over the years include recent novel transdermal, nasal, pulmonary and orally disintegrating tablets that provide consistent, precise, timely and more targeted drug delivery. Certain drug delivery systems may be associated with suboptimal outcomes in the elderly because of the nature of drug present, a lack of appreciation of the impact of age-related changes in drug absorption, distribution and clearance, the limited availability of pharmacokinetic, safety and clinical data. Polypharmacy, patient morbidity and poor adherence can also contribute to sub-optimal drug delivery systems outcomes in the elderly. The development of drug delivery systems for the elderly is a poorly realised opportunity, with each system having specific advantages and limitations. A key challenge is to provide the innovation that best meets the specific physiological, psychological and multiple drug requirements of individual elderly patients.

The Effect of Single and Multiple Doses of Rifampin on the Pharmacokinetics of Doravirine in Healthy Subjects

BACKGROUND AND OBJECTIVE

Doravirine is a novel, next-generation, non-nucleoside reverse transcriptase inhibitor in development for the treatment of human immunodeficiency virus-1 infection in combination with other antiretrovirals. Doravirine is a substrate for cytochrome P450 (CYP) 3A and P-glycoprotein. Rifampin (rifampicin) is used for treating tuberculosis in patients who are co-infected with human immunodeficiency virus. Rifampin demonstrates organic anion-transporting polypeptide 1B1 and P-glycoprotein inhibition after single-dose administration and CYP3A and P-glycoprotein induction after multiple-dose administration. The objective of this study was to evaluate the effects of co-administration of single and multiple doses of rifampin on doravirine pharmacokinetics.

METHODS

In period 1 of this open-label, two-period, fixed-sequence study in healthy adults, subjects received single-dose doravirine 100 mg; blood samples for measuring plasma concentration were collected pre-dose and up to 72 h post-dose. In period 2, following a 7-day washout, subjects received doravirine 100 mg and rifampin 600 mg on day 1, rifampin 600 mg daily on days 4-18, with doravirine 100 mg co-administered on day 17; blood samples were collected pre-dose and up to 72 h post-dose on day 1 and up to 48 h post-dose on day 17. Safety assessments included adverse events, physical examinations, vital signs, and clinical laboratory measurements.

RESULTS

Ten subjects completed the study. Doravirine area under the concentration-time curve from time zero extrapolated to infinity and plasma concentration at 24 h post-dose were comparable in the presence and absence of single-dose rifampin [geometric mean ratios (90% confidence intervals)] of 0.91 (0.78-1.06) and 0.90 (0.80-1.01), respectively. Doravirine maximum plasma concentration increased when co-administered with single-dose rifampin vs. doravirine alone, geometric mean ratio (90% confidence interval): 1.40 (1.21-1.63). Reductions in doravirine geometric mean ratios (90% confidence interval), area under the concentration-time curve from time zero extrapolated to infinity: 0.12 (0.10-0.15), plasma concentration at 24 h post-dose: 0.03 (0.02-0.04), maximum plasma concentration: 0.43 (0.35-0.52), and apparent terminal half-life were observed when co-administered with multiple-dose rifampin vs. doravirine administered alone. Doravirine was well tolerated. Adverse events were mild and resolved by study completion.

CONCLUSIONS

Doravirine co-administration with single-dose rifampin indicated that inhibition of organic anion-transporting polypeptide uptake transporters and P-glycoprotein has little impact on doravirine pharmacokinetics. Long-term co-administration of rifampin or other strong CYP3A inducers with doravirine will likely reduce its efficacy.

Potential Drug Interactions Mediated by Renal Organic Anion Transporter OATP4C1

Organic anion-transporting polypeptide 4C1 (OATP4C1) is an organic anion transporter expressed in the basolateral membrane of the renal proximal tubules. It plays a major role in the urinary excretion of both exogenous drugs and endogenous compounds. Our previous studies have indicated the importance of OATP4C1 in pathologic and physiologic conditions; however, the majority of its pharmacologic characteristics remained unclear. Therefore, to provide essential information for clinical drug therapy decisions and drug development, we clarified drug interactions mediated by OATP4C1. To elucidate potential drug interactions via OATP4C1, we screened 53 representative drugs commonly used in clinical settings. Next, we evaluated the IC₅₀ values of drugs that inhibited OATP4C1 by more than 50%. To apply our results to clinical settings, we calculated the drug-drug interaction (DDI) indices. The screening analysis using an OATP4C1-expressing cell system demonstrated that 22 out of 53 therapeutic drugs inhibited OATP4C1-mediated triiodothyronine transport. In particular, OATP4C1-mediated transport was strongly inhibited by 10 drugs. The IC₅₀ values of 10 drugs-nicardipine, spironolactone, fluvastatin, crizotinib, levofloxacin, clarithromycin, ritonavir, saquinavir, quinidine, and verapamil-obtained in this study were 51, 53, 41, 24, 420, 200, 8.5, 4.3, 100, and 110 µM, respectively. The IC₅₀ values of these drugs were higher than the plasma concentrations obtained in clinical practice. However, ritonavir showed the highest DDI index (1.9) for OATP4C1, suggesting that it may strongly influence this transporter and thus cause drug interactions seen in clinical settings. Our finding gives new insight into the role of OATP4C1 in clinical DDIs.

Development and validation of an improved HPLC-MS/MS method for comparative pharmacokinetics of penehyclidine hydrochloride following a single intravenous or intramuscular injection

Penehyclidine hydrochloride (PHC) is an anticholinergic drug with both antimuscarinic and antinicotinic activity. In order to compare the pharmacokinetics of two administration routes (intravenous injection (i.v.) and intramuscular injection (i.m.)) of PHC, an improved High Performance Liquid Chromatography Tandem Mass Spectrometry (HPLC-MS/MS) bioanalytical method was developed for the quantification of PHC in plasma and urine using verapamil as the internal standard (I.S.). Chromatography was performed using a Thermo Hypersil GOLD column (30mm×2.1mm, 3μm), with a gradient elution of 1‰ formic acid-10mmol/L ammonium acetate and acetonitrile at 0.3mL/min. Detection and quantitation were performed by electrospray ionization (ESI) and multiple reaction monitoring (MRM) in the positive ion mode. The most intense [M+H](+) MRM transition of PHC at m/z 316.2→128.3 was used for PHC quantitation, and the transition at m/z 454.6→303.2 was used to monitor I.S. The lower limit of quantification (LLOQ) was 0.05 ng/mL. The intraday precision was <6.71% and the interday precision was <11.69%. The pharmacokinetic parameters of i.v. and i.m. administration routes were as follows (i.v. vs i.m.): t1/2 15.73 vs 17.24h, Tmax 0.06 vs 0.26h, AUC0-t 69.35 vs 67.90hng/mL, AUC0-inf 78.24 vs 79.67hng/mL, Cmax 37.5 vs 9.1ng/mL, Ae0-24h 22.7 vs 25.21μg. There were no significant differences between parameters t1/2 and AUC (P>0.05), but significant differences were observed in Cmax, Tmax and Ae0-24h between the two administration routes (P<0.05). The mean absolute bioavailability of the i.m. administration route was 98.4% (95% confidence interval, 93.4-103.6%). Safety results showed that PHC appeared to be well tolerated in both i.v. and i.m. administration routes and pharmacokinetic results showed that PHC was nearly completely absorbed via i.m. administration route.

Hormonal regulation of hepatic drug biotransformation and transport systems

The human body is constantly exposed to many xenobiotics including environmental pollutants, food additives, therapeutic drugs, etc. The liver is considered the primary site for drug metabolism and elimination pathways, consisting in uptake, phase I and II reactions, and efflux processes, usually acting in this same order. Modulation of biotransformation and disposition of drugs of clinical application has important therapeutic and toxicological implications. We here provide a compilation and analysis of relevant, more recent literature reporting hormonal regulation of hepatic drug biotransformation and transport systems. We provide additional information on the effect of hormones that tentatively explain differences between sexes. A brief discussion on discrepancies between experimental models and species, as well as a link between gender-related differences and the hormonal mechanism explaining such differences, is also presented. Finally, we include a comment on the pathophysiological, toxicological, and pharmacological relevance of these regulations.

Gender medicine: a task for the third millennium

Gender-specific medicine is the study of how diseases differ between men and women in terms of prevention, clinical signs, therapeutic approach, prognosis, psychological and social impact. It is a neglected dimension of medicine. In this review we like to point out some major issues in five enormous fields of medicine: cardiovascular diseases (CVDs), pharmacology, oncology, liver diseases and osteoporosis. CVDs have been studied in the last decades mainly in men, but they are the first cause of mortality and disability in women. Risk factors for CVD have different impacts in men and women; clinical manifestations of CVD and the influence of drugs on CVD have lot of gender differences. Sex-related differences in pharmacokinetics and pharmacodynamics are also emerging. These differences have obvious relevance to the efficacy and side effect profiles of various medications in the two sexes. This evidence should be considered for drug development as well as before starting any therapy. Gender disparity in cancer incidence, aggressiveness and prognosis has been observed for a variety of cancers and, even if partially known, is underestimated in clinical practice for the treatment of the major types of cancer. It is necessary to systematize and encode all the known data for each type of tumor on gender differences, to identify where this variable has to be considered for the purposes of the prognosis, the choice of treatment and possible toxicity. Clinical data suggest that men and women exhibit differences regarding the epidemiology and the progression of certain liver diseases, i.e., autoimmune conditions, genetic hemochromatosis, non-alcoholic steatohepatitis and chronic hepatitis C. Numerous hypotheses have been formulated to justify this sex imbalance including sex hormones, reproductive and genetic factors. Nevertheless, none of these hypothesis has thus far gathered enough convincing evidence and in most cases the evidence is conflicting. Osteoporosis is an important public health problem both in women and men. On the whole, far more epidemiologic, diagnostic and therapeutic studies have been carried out in women than in men. In clinical practice, if this disease remains underestimated in women, patients' and physicians' awareness is even lower for male osteoporosis, for which diagnostic and therapeutic strategies are at present less defined. In conclusion this review emphasizes the urgency of basic science and clinical research to increase our understanding of the gender differences of diseases.

Sex and gender differences in cardiovascular drug therapy

This chapter outlines sex differences in pharmacokinetics and pharmacodynamics of the most frequently used drugs in cardiovascular diseases, e.g., coronary artery disease, hypertension, heart failure. Retrospective analysis of previously published drug trials revealed marked sex differences in efficacy and adverse effects in a number of cardiovascular drugs. This includes a higher mortality among women taking digoxin for heart failure, more torsade de pointes arrhythmia in QT prolonging drugs and more cough with ACE inhibitors. Trends towards a greater benefit for women and/or female animals have been observed in some studies for endothelin receptor antagonists, the calcium channel blocker amlodipine, the ACE-inhibitor ramipril and the aldosterone antagonist eplerenone. However, reproduction of these results in independent studies and solid statistical evidence is still lacking. Some drugs require a particularly careful dose adaptation in women: the beta-blocker metoprolol, the calcium channel blocker verapamil, loop-, and thiazide diuretics. In conclusion, sex differences in pharmacokinetics and pharmacodynamics have to be taken into account for cardiovascular drug therapy in women.

Applications of minimal physiologically-based pharmacokinetic models

Conventional mammillary models are frequently used for pharmacokinetic (PK) analysis when only blood or plasma data are available. Such models depend on the quality of the drug disposition data and have vague biological features. An alternative minimal-physiologically-based PK (minimal-PBPK) modeling approach is proposed which inherits and lumps major physiologic attributes from whole-body PBPK models. The body and model are represented as actual blood and tissue (usually total body weight) volumes, fractions (f ( d )) of cardiac output with Fick's Law of Perfusion, tissue/blood partitioning (K ( p )), and systemic or intrinsic clearance. Analyzing only blood or plasma concentrations versus time, the minimal-PBPK models parsimoniously generate physiologically-relevant PK parameters which are more easily interpreted than those from mammillary models. The minimal-PBPK models were applied to four types of therapeutic agents and conditions. The models well captured the human PK profiles of 22 selected beta-lactam antibiotics allowing comparison of fitted and calculated K ( p ) values. Adding a classical hepatic compartment with hepatic blood flow allowed joint fitting of oral and intravenous (IV) data for four hepatic elimination drugs (dihydrocodeine, verapamil, repaglinide, midazolam) providing separate estimates of hepatic intrinsic clearance, non-hepatic clearance, and pre-hepatic bioavailability. The basic model was integrated with allometric scaling principles to simultaneously describe moxifloxacin PK in five species with common K ( p ) and f ( d ) values. A basic model assigning clearance to the tissue compartment well characterized plasma concentrations of six monoclonal antibodies in human subjects, providing good concordance of predictions with expected tissue kinetics. The proposed minimal-PBPK modeling approach offers an alternative and more rational basis for assessing PK than compartmental models.

A GENS-based approach to cardiovascular pharmacology: impact on metabolism, pharmacokinetics and pharmacodynamics

Pharmacological outcomes depend on many factors, with many of them being sexually dimorphic. Thus, physiological gender/sex (GENS) differences can influence pharmacokinetics, pharmacodynamics and, thus, bioavailability and resulting in efficacy of treatment, meaning GENS differences should be an important consideration in therapeutics. In particular, drug response can change according to different hormonal environments. Therefore, GENS-specific differences have a particular clinical relevance in terms of drug delivery, especially for those substances with a narrow therapeutic margin. Since adverse effects are more frequent among women, safety is a key issue. Overall, the status of women, from a pharmacological point of view, is often different and less studied than that of men and deserves particular attention. Further studies focused on women's responses to drugs are necessary in order to make optimal pharmacotherapeutic decisions.

Sex differences in lopinavir and ritonavir pharmacokinetics among HIV-infected women and men

The authors compared the pharmacokinetics of lopinavir (LPV) and ritonavir (RTV) between women and men. This 2-step, multicenter, pharmacokinetic study enrolled human immunodeficiency virus (HIV)-infected adults on lopinavir/ritonavir (LPV/r) capsules (400/100 mg bid) plus 1 or more nucleoside reverse transcriptase inhibitors. All participants underwent 12-hour pharmacokinetic sampling. The pharmacokinetic sampling was repeated in participants receiving the LPV/r tablet formulation. Step 1 enrolled 37 women and 40 men; step 2 included 42 participants from step 1 plus 35 new participants (39 women and 38 men). LPV pharmacokinetics in women and men were not significantly different with either formulation. Women had significantly higher median RTV AUC(0-12 h) with both the soft-gel capsule (SGC) and tablet formulations (SGC: 5395 vs 4119 ng·h/mL, P = .026; tablet: 5310 vs 3941 ng·h/mL, P = .012), higher median C(max) (SGC: 802 vs 635 ng/mL, P = .032; tablet: 773 vs 570 ng/mL, P = .006), and lower median CL/F (SGC: 18.54 vs 24.31 L/h, P = .026; tablet: 18.83 vs 25.37 L/h, P = .012). RTV CL/F was slower in women after weight adjustment with both formulations. The pharmacokinetics of LPV in the SGC and tablet formulations are comparable in HIV-infected patients. Women had higher RTV AUC(0-12 h) and lower CL/F with both formulations. The mechanism of the sex difference in RTV CL/F warrants elucidation.

Hepatic clearance, but not gut availability, of erythromycin is altered in patients with end-stage renal disease

Nonrenal clearance of drugs can be significantly lower in patients with end-stage renal disease (ESRD) than in those with normal renal function. Using erythromycin (ER) as a probe compound, we investigated whether this decrease in nonrenal clearance is due to reduced hepatic clearance (CL(H)) and/or gut metabolism. We also examined the potential effects of the uremic toxins 3-carboxy-4-methyl-5-propyl-2-furan propanoic acid (CMPF) and indoxyl sulfate (Indox) on ER disposition. Route-randomized, two-way crossover pharmacokinetic studies of ER were conducted in 12 ESRD patients and 12 healthy controls after oral (250 mg) and intravenous (125 mg) dosing with ER. In patients with ESRD, CL(H) decreased 31% relative to baseline values (0.35 +/- 0.14 l/h/kg vs. 0.51 +/- 0.13 l/h/kg, P = 0.01), with no change in steady-state volume of distribution. With oral dosing, the bioavailability of ER increased 36% in patients with ESRD, and this increase was not related to changes in gut availability. As expected, plasma levels of CMPF and Indox were significantly higher in the patients than in the healthy controls. However, no correlation was observed between CL(H) of ER and the levels of uremic toxins.

Implications of gender and pregnancy for antiretroviral drug dosing

PURPOSE OF REVIEW

This review briefly outlines the influences of gender and pregnancy on drug disposition, and describes the available antiretroviral pharmacokinetic data and dosing recommendations in these groups.

RECENT FINDINGS

Recent studies in pregnant women continue to document altered exposure of different classes of drugs during pregnancy. While new information shows that tenofovir exposure is significantly decreased during pregnancy, the magnitude of the decrease will not likely necessitate dose changes, similar to other nucleoside reverse transcriptase inhibitors. In contrast, standard doses of lopinavir/ritonavir in the third trimester showed markedly decreased exposure, and higher doses of this co-formulated agent should be given to women during the third trimester. Likewise, nelfinavir exposure using the new 625-mg tablets is also decreased during pregnancy, and higher doses should be considered in the third trimester.

SUMMARY

The majority of antiretrovirals studied have altered pharmacokinetics during pregnancy. Understanding the extent of these changes is necessary to recommend dose changes during pregnancy when appropriate. The correct dose is critical to maintain efficacy and safety of these agents for both the mother and the fetus. Innovative study designs are needed to facilitate the study of antiretrovirals during pregnancy.

Patient Sex and its Influence on General Anaesthesia

Physiological and pharmacological differences exist between men and women. Women wake faster than men following general anaesthesia. Women also differ from men in their postoperative recovery as reflected by differences in postoperative pain, nausea and vomiting and overall quality of recovery. These gender differences seem to be more pronounced in premenopausal women, suggesting hormonal mechanisms are a major contributing factor.

Sex differences in pharmacokinetics and pharmacodynamics

Significant differences that exist between the sexes affect the prevalence, incidence and severity of a broad range of diseases and conditions. Men and women also differ in their response to drug treatment. It is therefore essential to understand these reactions in order to appropriately conduct risk assessment and to design safe and effective treatments. Even from that modest perspective, how and when we use drugs can result in unwanted and unexpected outcomes. This review summarizes the sex-based differences that impact on pharmacokinetics, and includes a general comparison of clinical pharmacology as it applies to men, women and pregnant women. Sex-related or pregnancy-induced changes in drug absorption, distribution, metabolism and elimination, when significant, may guide changes in dosage regimen or therapeutic monitoring to increase its effectiveness or reduce potential toxicity. Given those parameters, and our knowledge of sex differences, we can derive essentially all factors necessary for therapeutic optimization. Since this is a rapidly evolving area, it is essential for the practitioner to review drug prescribing information and recent literature in order to fully understand the impact of these differences on clinical therapeutics.

Sex-specific differences in CYP450 isoforms in humans

BACKGROUND

The activity of various CYP isoforms is critical for maintaining the clinical effectiveness of many medications. Therefore, determining the sex-dependent activity of clinically relevant CYP families is highly important for optimal therapeutic effectiveness.

OBJECTIVE

This review examined the sex-dependent activity of CYP3A, CYP1A2, CYP2D6, CYP2C9, CYP2C19 and CYP2E1.

METHODS

This review searched for studies performed in humans and hormonal status was not a limiting factor.

RESULTS/CONCLUSIONS

The current evidence suggests that CYP2E1 and CYP1A2 activity is higher in males than females, while CYP3A, one of the most clinically relevant CYP isoforms, appears to have greater activity in females. Overall, more studies are needed to fully support these conclusions as there are many factors that influence drug metabolism and thus it is very difficult to isolate gender as a sole modulator of CYP activity.

Sex differences in treatment patterns of six chronic diseases: an analysis from the German statutory health insurance

OBJECTIVE

The goal of this study was to investigate gender-specific differences in prevalence, healthcare costs, and treatment patterns in the German Statutory Health Insurance (SHI).

METHODS

The study analyzed administrative claims data of over 26 million insured with respect to prevalence and cost of illness of six chronic diseases. Insured were identified using the ATC code for medication prescription and ICD-9 code for diagnosis. The influences of gender, age, and comorbidity on cost differences were analyzed via multivariate regression analysis.

RESULTS

Adjusted for age and comorbidity, gender had a significant influence on both hospital and medication spending. Hospital costs on average were 17.1% (95% CI 14.1; 20.2) higher for men compared with women. Medication spending for men exceeded that for women on average by 13.8% (95% CI 10.9; 16.7). The diagnoses with the highest prevalence were hypertension and heart failure. Women had a higher prevalence of diabetes, coronary artery disease (CAD), heart failure, and hypertension. Medication costs were higher for men in three of five diagnoses and comparable for two diagnoses (diabetes and asthma). Women received more medication prescriptions than men, but on average prescriptions for men were 14%-26% more expensive than prescriptions for women. Regarding treatment patterns men were treated with different drug classes in cardiovascular disease (CVD) compared with women. Total medication spending stratified by diagnosis was highest for diabetes.

CONCLUSIONS

Gender differences for costs and prescribing patterns for chronic diseases vary disease specifically, but generally men had higher inpatient costs and more expensive medication prescriptions, whereas women had higher numbers of prescriptions.

Women encounter ADRs more often than do men

BACKGROUND

Several publications indicate that the female gender experiences a higher incidence of adverse drug reactions (ADRs) than does the male gender. The reasons, however, remain unclear. Gender-specific differences in the pharmacokinetic and pharmacodynamic behaviour of drugs could not be identified as an explanation. The aim of this study was to analyse ADR risk with respect to gender, age and number of prescribed drugs.

METHODS

A prospective multicenter study based on intensive pharmacovigilance was conducted. Information on patient characteristics and evaluated ADRs was stored in a pharmacovigilance database--KLASSE.

RESULTS

In 2,371 patients (1,012 female subjects), 25,532 drugs were prescribed. In 782 patients, at least one ADR was found. A multivariate regression analysis adjusting for age, body mass index (BMI) and number of prescribed drugs showed a significant influence of female gender on the risk of encountering ADRs [odds ratio (OR) 1.596, confidence interval (CI) 1.31-1.94; p < 0.0001). Dose-related ADRs (51.8%) were the dominant type in female subjects. Comparing system organ classes of the World Health Organisation (SOC-WHO), cardiovascular (CV) ADRs were particularly frequent in female subjects (OR 1.92, CI 1.15-3.19; p = 0.012).

CONCLUSION

Our data confirm the higher risk of ADRs among female subjects compared with a male cohort. Several explanations were investigated. No single risk factor could be identified.

Polyethylene glycol 400 enhances the bioavailability of a BCS class III drug (ranitidine) in male subjects but not females

PURPOSE

The aim of this study was to investigate the effects of different doses of polyethylene glycol 400 (PEG 400) on the bioavailability of ranitidine in male and female subjects.

METHOD

Ranitidine (150 mg) was dissolved in 150 ml water with 0 (control), 0.5, 0.75, 1, 1.25 or 1.5 g PEG 400 and administered to 12 healthy human volunteers (six males and six females) in a randomized order. The cumulative amount of ranitidine and its metabolites excreted in urine over 24 h was determined for each treatment using a validated HPLC method.

RESULTS

In the male volunteers, the mean cumulative amount of ranitidine excreted in the presence of 0, 0.5, 0.75, 1, 1.25 and 1.5 g PEG 400 were 35, 47, 57, 52, 50 and 37 mg respectively. These correspond to increases in bioavailability of 34%, 63%, 49%, 43% and 6% over the control treatment. In the female subjects, the mean cumulative quantity of ranitidine excretion in the absence and presence of increasing amounts of PEG 400 were 38, 29, 35, 33, 33 and 33 mg, corresponding to decreases in bioavailability of 24%, 8%, 13%, 13% and 13% compared to the control. The metabolite excretion profiles followed a similar trend to the parent drug at all concentrations of PEG 400.

CONCLUSIONS

All doses of PEG 400 enhanced the bioavailability of ranitidine in male subjects but not females, with the most pronounced effect in males noted with the 0.75 g dose of PEG 400 (63% increase in bioavailability compared to control, p < 0.05). These findings have significant implications for the use of PEG 400 in drug development and also highlight the importance of gender studies in pharmacokinetics.

The effect of gender on the pharmacokinetics of verapamil and norverapamil in human

The effects of gender on the pharmacokinetics of verapamil and its active metabolite, norverapamil, following single oral dose (80 mg, Isoptin) to 12 healthy male (mean age: 25.75+/-2.42 years, mean body weight: 70.59+/-9.94 kg) and 12 healthy female subjects (mean age: 24.08+/-2.84 years, mean body weight: 56.67+/-5.23 kg) were investigated in the present study. Plasma concentrations of verapamil and norverapamil were analysed using a modified high-pressure liquid chromatography method. Pharmacokinetic parameters were calculated by non-compartmental analysis for each subject. For verapamil the half-life (t1/2) and mean residence time (MRT) were significantly shorter in women than men (p<0.01 and p<0.05, respectively). For other pharmacokinetic parameters of verapamil there were no significant differences between males and females. For norverapamil, t1/2, MRT and time to reach to the maximum plasma concentration (Tmax) showed statistically significant differences between the two genders. The AUC(0-24) and AUC(0-infinity) ratios of norverapamil to verapamil were also calculated. The ratios were significantly higher in women compared with men. These observations indicate that the elimination rate of verapamil is faster in women than men which may be attributed to the higher activity of CYP3A4 or lower activity of P-glycoprotein in women compared with men. A contribution of both factors in the appearance of gender differences in verapamil pharmacokinetics is also possible.

The Current State of Knowledge on Age, Sex, and Their Interactions on Clinical Pharmacology

Pharmacokinetic and pharmacodynamic changes occur with increasing age. Sex differences in pharmacokinetics and pharmacodynamics exist and persist at older age. The issue for the clinician is how to best treat the older patient with currently available knowledge. This communication highlights age- and sex-related differences in pharmacokinetics that should influence clinical practice and prescribing guidelines to optimize clinical responses. The most compelling data for sex-specific medication dosing guidelines for older patients are related to volume of distribution differences, or size differences, between the sexes and to differences in glomerular filtration rates.

Cytochrome P450 3A5 genotype is associated with verapamil response in healthy subjects

We hypothesized that CYP3A5 genotype contributes to the interindividual variability in verapamil response. Healthy subjects (n=26) with predetermined CYP3A5 genotypes were categorized as expressers (at least one CYP3A5(*)1 allele) and nonexpressers (subjects without a CYP3A5(*)1 allele). Verapamil pharmacokinetics and pharmacodynamics were determined after 7 days of dosing with 240 mg daily. There was a significantly higher oral clearance of R-verapamil (165.1+/-86.4 versus 91.2+/-36.5 l/h; P=0.009) and S-verapamil (919.4+/-517.4 versus 460.2+/-239.7 l/h; P=0.01) in CYP3A5 expressers compared to nonexpressers. Consequently, CYP3A5 expressers had significantly less PR-interval prolongation (19.5+/-12.3 versus 44.0+/-19.4 ms; P=0.0004), and had higher diastolic blood pressure (69.2+/-7.5 versus 61.6+/-5.1 mm Hg; P=0.036) than CYP3A5 nonexpressers after 7 days dosing with verapamil. CYP3A5 expressers display a greater steady-state oral clearance of verapamil and may therefore experience diminished pharmacological effect of verapamil due to a greater steady state oral clearance.

Validation of the hepatic blood flow rate model for verapamil first-pass metabolism

The bioavailability of a new retard tablet formulation of verapamil was investigated in a randomized cross-over bioequivalence study on 12 healthy subjects. The drug was given in the form of a single 240-mg oral dose of a new retard tablet formulation, or as a standard retard tablet at the same dose to all subjects, followed by a single intravenous (i.v.) dose of 5 mg to 8 of the 12 subjects. Plasma verapamil concentrations were determined by a high performance liquid chromatography (HPLC) method. The bioavailability of the new peroral retard formulation was (20.00 +/- 4.30)% and was in reasonable agreement with that determined for the already registered verapamil retard formulation, i.e. (19.46 +/- 4.02)%, thereby indicating bioequivalence. For the prediction of systemic availability and estimation of the first-pass metabolism, only based on the data for peroral plasma levels, a hepatic blood flow rate limited model was used. In our experience, this model has been found to be extremely useful in providing reasonable estimates of verapamil first-pass effect.