Sex-related differences in drug disposition in man

Adverse Drug Reaction Patterns of First-line Anti-tubercular Drugs among Saharia Tuberculosis Patients: An Observational Study in Particularly Vulnerable Tribal Group of Madhya Pradesh, India

SUMMARY

The Saharia tribe of Madhya Pradesh has a very high tuberculosis (TB) burden. However, there is no report of adverse drug reaction (ADR) available in patients receiving anti-TB chemotherapy in the community. Reporting and monitoring of ADRs among TB patients is still rare in marginalized communities. An observational prospective study was performed from November 2019 to June 2020 to assess the patterns of ADRs in 250 Saharia TB patients, who were prescribed Category-I daily DOTS (HRZE) by the physician. Both male and female participants equally experienced ADR during the treatment, but relatively more females (92.6%) than males (88.6%) reported ADR during Phase I. Out of 250 patients, 224 patients (89.6%) experienced one or more ADRs in Phase I. The central nervous system-related (75.6%) ADR was mostly reported followed by any gastrointestinal (74.4%), cardiovascular (49.2%) and any dermatological related (44.4%) ADRs. It is paramount to timely monitor and proactively manages ADRs pertaining to anti-TB drug treatment with minimal alteration in the treatment course.

Andrographis paniculata mitigates first-line anti-tubercular drugs-induced nephrotoxicity in Wistar rats

CONTEXT

Anti-tubercular drugs (ATDs) mediated adverse drug reactions are major concerns for clinicians to treat tuberculosis infection. This study aimed to investigate Andrographis paniculata extract-based phytotherapy to combat the nephrotoxic effects caused by ATDs therapy.

METHODS

Reno-protective effect of A. paniculata extract in ATDs-induced rats was evaluated through LPO, GSH, CAT, SOD, GST, urea, creatinine, uric acid, and histopathological studies. Standardization of the extract was performed RP-HPLC and FTIR analysis. Whereas, the effect of A. paniculata extract on ATDs induced genetic perturbation was analyzed using micronucleus assay. Moreover, the expression level of the xenometabolic gene was investigated using RT-PCR to explore the therapeutic mechanism.

RESULTS

The nephrotoxic effect of ATDs was indicated by elevated levels of LPO and renal function markers along with the reduced activity of renal antioxidants. An up-regulated expression profile of NAT gene and histological alterations were observed in renal tissue however, micronucleated PCEs were observed in bone marrow cells. Concomitant treatment with A. paniculata extract revealed a noticeable amelioration of elevated oxidative stress markers, gene expression levels, genotoxic perturbation, and histological alterations in a dose-dependent manner.

CONCLUSION

Hence, the present study using A. paniculata leaf extract confirmed to play effective phytotherapy against ATDs induced renal toxicity.

Metabolizer phenotype prediction in different Peruvian ethnic groups through CYP2C9 polymorphisms

OBJECTIVES

The CYP2C9 gene have three common alleles, CYP2C9*1, CYP2C9*2 and CYP2C9*3, associated with different homozygous (*1/*1, *2/*2 and *3/*3) and heterozygous (*1/*2 and *1/*3) genotypes, which in turn are related to extensive (gEM), intermediate (gIM) and poor (gPM) metabolizers. Likewise, the inter-ethnic variability was intimately associated with different drug metabolism. Therefore, the aim of the present study was predict the metabolizer phenotypes in different Peruvian ethnic groups from lowland (<2,500 m) and highland (>2,500 m).

METHODS

TaqMan genotyping assays were performed in a group of 174 healthy unrelated Peruvian individuals.

RESULTS

In this study, the allelic comparison between the three eco-regions showed that the CYP2C9*1 was the most common in Andean (96.32%); the *2 was the most frequent in Coast (7.45%, p<0.05). Regarding the *3 was the most common in Amazonian (6.25%, p<0.05). In a corroborative manner, the gEM was the most common in Andean (94.74%), the gIM in Coast (17.02%) and gPM in Amazonian (6.25%) populations.

CONCLUSIONS

Our study provides a valuable source of information about to metabolizer phenotype drugs in different Peruvian ethnic groups. In this way, it could be established suitable genetic-dosage medicaments for various common diseases in these heterogenetic populations.

PHARMACOKINETICS OF ORALLY ADMINISTERED FLUNIXIN MEGLUMINE IN AFRICAN (LOXODONTA AFRICANA) AND ASIAN (ELEPHAS MAXIMUS) ELEPHANTS

Flunixin meglumine is the most commonly used nonsteroidal anti-inflammatory drug used to treat elephants; however, no pharmacokinetic study for flunixin has yet been conducted in these species, and dosages used range widely. Pharmacokinetic parameters of flunixin were determined in African (Loxodonta africana) and Asian (Elephas maximus) elephants after single-dose oral administration of 0.8 and 1.5 mg/kg flunixin paste in each species. Elephant compliance to oral administration of banamine was occasionally challenging, especially among older, female African elephants. After administration of 0.8 mg/kg flunixin, mean serum concentrations peaked in approximately 1.3 hr at 2.1 ± 0.8 µg/ml for Asian (n = 8) and 2.8 hr at 2.5 ± 0.7 µg/ml for African (n = 8) elephants. Dosages of 1.5 mg/kg flunixin resulted in mean serum concentration peaks of 7.2 ± 1.5 µg/ml in Asian elephants (n = 7) and 4.4 ± 0.7 µg/ml in African elephants (n = 6). However, multiple-dose trials using 1.1 mg/kg flunixin resulted in peak serum concentrations that were again less in Asian than African elephants (2.7 µg/ml versus 4.4 µg/ml, respectively). Asian elephants consistently had lower time to maximal concentration, greater area under the curve, and longer mean residence times compared with African elephants. In other species, flunixin is excreted unchanged primarily via hepatic routes with small amounts in the urine. Asian elephants may engage in some level of enterohepatic recycling of flunixin, as was previously reported for phenylbutazone. This study supports that different oral dosing regimens should be used for Asian (1.0 mg/kg SID) and African (1.2 mg/kg SID) elephants, and oral administration techniques used should ensure complete dosage delivery.

Pharmacogenetic Testing: A Tool for Personalized Drug Therapy Optimization

Pharmacogenomics is a study of how the genome background is associated with drug resistance and how therapy strategy can be modified for a certain person to achieve benefit. The pharmacogenomics (PGx) testing becomes of great opportunity for physicians to make the proper decision regarding each non-trivial patient that does not respond to therapy. Although pharmacogenomics has become of growing interest to the healthcare market during the past five to ten years the exact mechanisms linking the genetic polymorphisms and observable responses to drug therapy are not always clear. Therefore, the success of PGx testing depends on the physician's ability to understand the obtained results in a standardized way for each particular patient. The review aims to lead the reader through the general conception of PGx and related issues of PGx testing efficiency, personal data security, and health safety at a current clinical level.

Gender-dependent pharmacokinetics of olaparib in rats determined by ultra-high performance liquid chromatography/electrospray ionization tandem mass spectrometry

The aim of the present study was to develop a liquid chromatography/electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method for the determination of olaparib in rat plasma. The plasma samples were processed using one-step protein precipitation with acetonitrile and then separated on Waters Acquity BEH C₁₈ column (50 × 2.1 mm, particle size 1.7 μm) using water containing 0.1% formic acid and acetonitrile as mobile phase with optimized gradient elution. Mass spectrometric detection was carried out by selective reaction monitoring mode via positive ESI mode with precursor-to-product transitions of m/z 435.3 > 367.1 and m/z 443.1 > 375.2 for olaparib and ² H₈ -olaparib (internal standard). The method was linear over the concentration range 0.1-2000 ng/ml with correlation coefficient >0.9987. The lower limit of quantitation was 0.1 ng/ml. The method showed excellent accuracy and precision, negligible matrix effect and high extraction recovery. The validated method was subsequently utilized to determine the concentration of olaparib in rat plasma and further applied to the pharmacokinetic study of olaparib in rat plasma. Our results demonstrated that olaparib showed gender-dependent pharmacokinetics in rats. Compared with that in males, olaparib showed high plasma exposure, long half-life, low clearance and high bioavailability in females.

Effect of Gender on the Pharmacokinetics of ON 123300, A Dual Inhibitor of ARK5 and CDK4/6 for the Treatment of Cancer, in Rats

BACKGROUND AND OBJECTIVES

ON 123300, a small molecule dual inhibitor of the c-MYC activated kinases ARK5 and CDK4/6, is being developed as a novel drug candidate for the treatment of cancer. The objective of this research was to evaluate gender differences in the in vitro metabolism and in vivo systemic exposure of ON 123300 in rats.

METHODS

In vitro metabolism experiments (n = 2/group) were performed in rat liver microsomes from male and female donors. ON 123300 bislactate (final concentration 10 µM) was incubated with 0.5 mg/mL microsomes, and samples (100 µL) were withdrawn at specified incubation times over a period of 60 min, and immediately quenched and centrifuged. The supernatant was analyzed for ON 123300 and its metabolites by HPLC. ON 123300 (bislactate salt) pharmacokinetics were evaluated following intravenous (i.v.) (30 s infusion, 5 and 10 mg/kg) or oral administration (25 and 100 mg/kg) to male and female Sprague-Dawley rats (250-300 g). Following dosing, blood samples were collected over a time period up to 24 h. ON 123300 plasma concentrations were measured by LC-MS/MS. Pharmacokinetic parameters were estimated by non-compartmental analysis. Plasma and microsomal binding of ON 123300 and blood:plasma ratio were also determined.

RESULTS

ON 123300 displayed more rapid microsomal degradation in vitro in males compared to females, as reflected in intrinsic clearance (181 vs 53.1 µL/min/mg). This translated into a significantly higher exposure of ON 123300 following oral administration to female rats, with the area under the curve (AUC) increasing nearly 3-fold (5617 ± 1914 ng·h/mL) compared to males (AUC = 1965 ± 749 ng·h/mL). This gender effect was less pronounced following i.v. dosing, where the AUC was ~ 2-fold higher in females. Based on these results, the higher plasma exposure observed in females can be primarily attributed to reductions in both hepatic clearance and presystemic metabolism compared to males.

CONCLUSIONS

This investigation demonstrated a significantly lower metabolism of ON 123300 in female rats, which resulted in high systemic exposure. Additional testing is warranted to assess the potential clinical implications of these findings.

Molecular Markers in Sex Differences in Cancer

Cancer is one of the common causes of death with a high degree of mortality, worldwide. In many types of cancers, if not all, sex-biased disparities have been observed. In these cancers, an individual's sex has been shown to be one of the crucial factors underlying the incidence and mortality of cancer. Accumulating evidence suggests that differentially expressed genes and proteins may contribute to sex-biased differences in male and female cancers. Therefore, identification of these molecular differences is important for early diagnosis of cancer, prediction of cancer prognosis, and determination of response to specific therapies. In the present review, we summarize the differentially expressed genes and proteins in several cancers including bladder, colorectal, liver, lung, and non-small cell lung cancers as well as renal clear cell carcinoma, and head and neck squamous cell carcinoma. The sex-biased molecular differences were identified via proteomics, genomics, and big data analysis. The identified molecules represent potential candidates as sex-specific cancer biomarkers. Our study provides molecular insights into the impact of sex on cancers, suggesting strategies for sex-biased therapy against certain types of cancers.

Sex- and age-related changes in GABA signaling components in the human cortex

Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the nervous system. Previous studies have shown fluctuations in expression levels of GABA signaling components-glutamic acid decarboxylase (GAD), GABA receptor (GABAR) subunit, and GABA transporter (GAT)-with increasing age and between sexes; however, this limited knowledge is highly based on animal models that produce inconsistent findings. This study is the first analysis of the age- and sex-specific changes of the GAD, GABAA/BR subunits, and GAT expression in the human primary sensory and motor cortices; superior (STG), middle (MTG), and inferior temporal gyrus (ITG); and cerebellum. Utilizing Western blotting, we found that the GABAergic system is relatively robust against sex and age-related differences in all brain regions examined. However, we observed several sex-dependent differences in GABAAR subunit expression in STG along with age-dependent GABAAR subunit and GAD level alteration. No significant age-related differences were found in α1, α2, α5, β3, and γ2 subunit expression in the STG. However, we found significantly higher GABAAR α3 subunit expression in the STG in young males compared to old males. We observed a significant sex-dependent difference in α1 subunit expression: males presenting significantly higher levels compared to women across all stages of life in STG. Older females showed significantly lower α2, α5, and β3 subunit expression compared to old males in the STG. These changes found in the STG might significantly influence GABAergic neurotransmission and lead to sex- and age-specific disease susceptibility and progression.

National strategy for the integration of pharmacovigilance in the Moroccan TB Control Program

The objective of this work is to demonstrate the interest of integration of pharmacovigilance in Moroccan Tuberculosis Control Program (MTCP). The integration of pharmacovigilance in MTCP was conducted in October 2012with the Global Fund support. We compared the reports notified before and after this integration (period 1: January 2010-October2012; period 2: October 2012-December 2013). The detection of signals was based on the Information Component available inVigiMine. We used the SPSS version 10.0 and Med Calc version 7.3 for data analysis. The average number of spontaneous reports increased from 3.6 to 37.4 cases/month (P< 10-3). The average age was 40.7 ± 17.5 years; the sex ratio was 0.8. Hepatic reactions (32.7%) predominated during the first period, while skin reactions (24.1%) were in the second period (P = 10-4), and40.9% of cases in the first period were serious against 15.8% in second period (P = 0.003). Nine signals were generated (hepaticenzyme increase, cholestasis, jaundice, arthralgia, acne, lower limb edema, pruritus, skin rashes, and vomiting). The integration of pharmacovigilance in Moroccan Tuberculosis Control Program improved the management of ADRs and detected new signals of antituberculosis drugs.

Sex Differences in Human and Animal Toxicology

Sex, the states of being female or male, potentially interacts with all xenobiotic exposures, both inadvertent and deliberate, and influences their toxicokinetics (TK), toxicodynamics, and outcomes. Sex differences occur in behavior, exposure, anatomy, physiology, biochemistry, and genetics, accounting for female-male differences in responses to environmental chemicals, diet, and pharmaceuticals, including adverse drug reactions (ADRs). Often viewed as an annoying confounder, researchers have studied only one sex, adjusted for sex, or ignored it. Occupational epidemiology, the basis for understanding many toxic effects in humans, usually excluded women. Likewise, Food and Drug Administration rules excluded women of childbearing age from drug studies for many years. Aside from sex-specific organs, sex differences and sex × age interactions occur for a wide range of disease states as well as hormone-influenced conditions and drug distribution. Women have more ADRs than men; the classic sex hormone paradigm (gonadectomy and replacement) reveals significant interaction of sex and TK including absorption, distribution, metabolisms, and elimination. Studies should be designed to detect sex differences, describe the mechanisms, and interpret these in a broad social, clinical, and evolutionary context with phenomena that do not differ. Sex matters, but how much of a difference is needed to matter remains challenging.

Resistance to cancer chemotherapy: failure in drug response from ADME to P-gp

Cancer chemotherapy resistance (MDR) is the innate and/or acquired ability of cancer cells to evade the effects of chemotherapeutics and is one of the most pressing major dilemmas in cancer therapy. Chemotherapy resistance can arise due to several host or tumor-related factors. However, most current research is focused on tumor-specific factors and specifically genes that handle expression of pumps that efflux accumulated drugs inside malignantly transformed types of cells. In this work, we suggest a wider and alternative perspective that sets the stage for a future platform in modifying drug resistance with respect to the treatment of cancer.

Pharmacovigilance and moroccan tuberculosis public program: current situation

The objective of this work is to demonstrate the interest of integration of pharmacovigilance in Moroccan Tuberculosis Control Program (MTCP). Design and Data Collection. The integration of pharmacovigilance in MTCP was conducted in October 2012 with the Global Fund support. We compared the reports notified before and after this integration (period 1: January 2010–October 2012; period 2: October 2012–December 2013). The detection of signals was based on the Information Component available in VigiMine. We used the SPSS version 10.0 and MedCalc version 7.3 for data analysis. Results. The average number of spontaneous reports increased from 3.6 to 37.4 cases/month (P < 10⁻³). The average age was 40.7 ± 17.5 years; the sex ratio was 0.8. Hepatic reactions (32.7%) predominated during the first period, while skin reactions (24.1%) were in the second period (P = 10⁻⁴), and 40.9% of cases in the first period were serious against 15.8% in second period (P = 0.003). Nine signals were generated (hepatic enzyme increase, cholestasis, jaundice, arthralgia, acne, lower limb edema, pruritus, skin rashes, and vomiting). Conclusion. The integration of pharmacovigilance in Moroccan Tuberculosis Control Program improved the management of ADRs and detected new signals of antituberculosis drugs.

Losartan hydroxylation phenotype in an Ecuadorian population: influence of CYP2C9 genetic polymorphism, habits and gender

AIM

To describe for the first time CYP2C9 hydroxylation phenotype with CYP2C9 genotypes in a Hispanic (Ecuadorian) population using losartan; and the relevance of gender, tobacco, ethanol and caffeine consumption on the enzyme hydroxylation capacity.

METHODS

Ecuadorian healthy volunteers (n = 194) received a single oral dose of 25 mg losartan. Losartan metabolic ratio was defined as losartan:E3174 concentration. CYP2C9 alleles *2, *3, *4, *5 and *6 were analyzed.

RESULTS

No phenotypically poor metabolizers were found. The metabolic ratio (mean ± standard deviation) was higher (p < 0.05) in CYP2C9*1/*3 carriers (12.4 ± 13.8; n = 6) versus CYP2C9*1/*1 (4.9 ± 7.0; n = 167), as well as in females versus males (6.72 ± 9.72 and 3.76 ± 4.48, respectively; p < 0.05). Only the following genotypes, CYP2C9*1/*1, CYP2C9*1/*2 and CYP2C9*1/*3, were found with a frequency of 86.1%, 10.8% and 3.1%, respectively.

CONCLUSION

Despite the mean metabolic ratio being higher in this population than in others previously studied across genotypes, no poor metabolizers, either phenotypically or genotypically, were found.

Pharmacokinetics and pharmacodynamics of psychotropic drugs: effect of sex

Data on the specific effects of sex on pharmacokinetics, as well as tolerability, safety, and efficacy of psychotropic medications are still meager, mainly because only recently sex-related issues have attracted a certain degree of interest within the pharmacological domain. Therefore, with the present study, we aimed to provide a comprehensive review of the literature on this topic, through careful MEDLINE and PubMed searches of the years 1990-2012. Generally, data on pharmacokinetics are more consistent and numerous than those on pharmacodynamics. Sex-related differences have been reported for several parameters that influence pharmacokinetics, such as gastric acidity, intestinal motility, body weight and composition, blood volume, liver enzymes (mainly the cytochrome P450), or renal excretion, which may alter plasma drug levels. Sex-related peculiarities may also account for a different sensitivity of men and women to side effects and toxicity of psychotropic drugs. Further, some differences in drug response, mainly to antipsychotics and antidepressants, have been described. Further studies are, however, necessary to explore more thoroughly the impact of sex on the pharmacokinetics and pharmacodynamics of psychotropic drugs, in order to reach the most appropriate and tailored prescription for each patient.

[Gender aspects in anesthesia : modified approach in research and treatment?]

Gender differences can have a relevant influence on the perioperative outcome as male and female patients are affected differently by adverse events, e.g. side effects of drugs. Furthermore, differences relating to specific drug effects, comorbidities and outcome after anesthesia or intensive care have been demonstrated. There seems to be a gender bias in diagnosis and therapy. While the knowledge regarding this field is still growing certain aspects have already been integrated into clinical practice: prevention of postoperative nausea and vomiting (PONV), target controlled infusion (TCI) model and male only policy with production of blood products. There is a need to study the influence of gender, age and race in order to optimize treatment towards a more individualized therapy. This article highlights already identified differences and discusses potential underlying mechanisms.

Adverse drug reaction reporting in a pharmacovigilance centre of Nepal

BACKGROUND

Pharmacovigilance is the "science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other drug related problems". Nepal joined the international pharmacovigilance programme as a full member in 2007. KIST Medical College, Lalitpur, Nepal joined the national programme as a regional centre from mid-July 2008. Currently, the pattern and scope of adverse drug reactions (ADRs) in Nepal remains unexplored.

AIMS

To observe and analyse the pattern of ADRs at KIST Medical College, Lalitpur, Nepal.

METHOD

A retrospective analysis of all ADRs reported to the centre from mid July 2008 to July 2011 was performed. Data was analysed for ADR severity, causality, and preventability.

RESULTS

A total of 113 ADR reports were obtained from various clinical departments. The maximum number of reactions was due to antimicrobials, followed by anti-hypertensives and NSAIDs.

CONCLUSION

Antimicrobials were the commonest group of drugs causing ADRs and the most commonly seen ADR was maculopapular rash followed by diarrhea and vomiting.

Adverse drug reaction reporting in a pharmacovigilance centre of Nepal

BACKGROUND

Pharmacovigilance is the "science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other drug related problems". Nepal joined the international pharmacovigilance programme as a full member in 2007. KIST Medical College, Lalitpur, Nepal joined the national programme as a regional centre from mid-July 2008. Currently, the pattern and scope of adverse drug reactions (ADRs) in Nepal remains unexplored.

AIMS

To observe and analyse the pattern of ADRs at KIST Medical College, Lalitpur, Nepal.

METHOD

A retrospective analysis of all ADRs reported to the centre from mid July 2008 to July 2011 was performed. Data was analysed for ADR severity, causality, and preventability.

RESULTS

A total of 113 ADR reports were obtained from various clinical departments. The maximum number of reactions was due to antimicrobials, followed by anti-hypertensives and NSAIDs.

CONCLUSION

Antimicrobials were the commonest group of drugs causing ADRs and the most commonly seen ADR was maculopapular rash followed by diarrhea and vomiting.

Gender differences in pharmacokinetics of lumefantrine and its metabolite desbutyl-lumefantrine in rats

Lumefantrine has been reported to be mainly bio-transformed by cytochrome P450 isozyme 3A4 to desbutyl-lumefantrine (DLF) in human liver microsomes. Since CYP3A is expressed in a sex specific manner in rats, it could be expected that the pharmacokinetics of lumefantrine would be changed in male rats compared with those in female rats. The pharmacokinetics of lumefantrine and its active metabolite DLF were evaluated after intravenous (0.5 mg/kg) and oral (20 mg/kg) administration of lumefantrine to male and female Sprague-Dawley rats. The quantitative bioanalysis was carried out by the liquid chromatography tandem mass spectrometry method. After intravenous and oral administration of lumefantrine the area under the curve (AUC) of lumefantrine was significantly higher in female rats than that in male rats, whereas the AUC of DLF was significantly lower in female rats in comparison with male rats. This lower AUC of DLF in female rats could have been due to reduced metabolism of lumefantrine in female rats. The bioavailability (%F) of lumefantrine was 1.66 times higher in male rats than that in female rats.

Pharmacokinetics of orally administered phenylbutazone in African and Asian elephants (Loxodonta africana and Elephas maximus)

The pharmacokinetic parameters of phenylbutazone were determined in 18 elephants (Loxodonta africana and Elephas maximus) after single-dose oral administration of 2, 3, and 4 mg/kg phenylbutazone, as well as multiple-dose administrations with a 4-wk washout period between trials. After administration of 2 mg/kg phenylbutazone, mean serum concentrations peaked in approximately 7.5 hr at 4.3 +/- 2.02 microg/ml and 9.7 hr at 7.1 +/- 2.36 microg/ml for African and Asian elephants, respectively, while 3 mg/kg dosages resulted in peak serum concentrations of 7.2 +/- 4.06 microg/ml in 8.4 hr and 12.1 +/- 3.13 microg/ml in 14 hr. The harmonic mean half-life was long, ranging between 13 and 15 hr and 39 and 45 hr for African and Asian elephants, respectively. There was evidence of enterohepatic cycling of phenylbutazone in Asian elephants. Significant differences (P < 0.0001) in pharmacokinetic values occurred between African and Asian elephants for clearance (27.9 and 7.6 ml/hr/kg, respectively), terminal half-life (15.0 and 38.7 hr, respectively), and mean residence time (22.5 and 55.5 hr, respectively) using 2-mg/kg dosages as an example. This suggests that different treatment regimens for Asian and African elephants should be used. There were no apparent gender differences in these parameters for either elephant species.

Sex differences in pharmacokinetics and toxicity of antiretroviral therapy

Worldwide, the rate of new HIV infections continues to increase among women. Over the past 5 years there has been a growing focus on the clinical aspects of HIV infection among women. Historically, the majority of subjects enrolled in HIV clinical trials were male patients. Consequently, most knowledge about antiretroviral efficacy and toxicity has been derived from studies of predominately male subjects. More recently, results from clinical trials, especially those that have focused on HIV-infected female subjects, suggest that there may be clinically important gender-related differences in several aspects of HIV disease. These include, but are not limited to, differences in natural history, efficacy and safety of drug treatment. This chapter reviews current data on gender differences in antiretroviral pharmacokinetics and toxicity.

Pharmacokinetics and pharmacodynamics in clinical use of scopolamine

The alkaloid L-(-)-scopolamine [L-(-)-hyoscine] competitively inhibits muscarinic receptors for acetylcholine and acts as a nonselective muscarinic antagonist, producing both peripheral antimuscarinic properties and central sedative, antiemetic, and amnestic effects. The parasympatholytic scopolamine, structurally very similar to atropine (racemate of hyoscyamine), is used in conditions requiring decreased parasympathetic activity, primarily for its effect on the eye, gastrointestinal tract, heart, and salivary and bronchial secretion glands, and in special circumstances for a CNS action. Therefore, scopolamine is most suitable for premedication before anesthesia and for antiemetic effects. This alkaloid is the most effective single agent to prevent motion sickness. Scopolamine was the first drug to be made commercially available in a transdermal therapeutic system (TTS-patch) delivering alkaloid. Recently, pharmacokinetic data on scopolamine in different biozlogic matrices were obtained most efficiently using liquid chromatographic-tandem mass spectrometric (LC-MS/MS) or gas chromatography online coupled to mass spectrometry. Pharmacokinetic parameters are dependent on the dosage form (oral dose, tablets; parenteral application; IV infusion; SC and IM injection). Scopolamine has a limited bioavailability if orally administered. The maximum drug concentration occurs approximately 0.5 hours after oral administration. Because only 2.6% of nonmetabolized L-(-)-scopolamine is excreted in urine, a first-pass metabolism is suggested to occur after oral administration of scopolamine. Because of its short half-life in plasma and dose-dependent adverse effects (in particular hallucinations and the less serious reactions, eg, vertigo, dry mouth, drowsiness), the clinical use of scopolamine administered orally or parenterally is limited. To minimize the relatively high incidence of side effects, the transdermal dosage form has been developed. The commercially available TTS-patch contains a 1.5-mg drug reservoir and a priming dose (140 microg) to reach the steady-state concentration of scopolamine quickly. The patch releases 0.5 mg alkaloid over a period of 3 days (releasing rate 5 microg/h). Following the transdermal application of scopolamine, the plasma concentrations of the drug indicate major interindividual variations. Peak plasma concentrations (Cmax) of approximately 100 pg/mL (range 11-240 pg/mL) of the alkaloid are reached after about 8 hours and achieve steady state. During a period of 72 hours the plaster releases scopolamine, so constantly high plasma levels (concentration range 56-245 pg/mL) are obtained, followed by a plateau of urinary scopolamine excretion. Although scopolamine has been used in clinical practice for many years, data concerning its metabolism and the renal excretion in man are limited. After incubation with beta-glucuronidase and sulfatase, the recovery of scopolamine in human urine increased from 3% to approximately 30% of the drug dose (intravenously administered). According to these results from enzymatic hydrolysis of scopolamine metabolites, the glucuronide conjugation of scopolamine could be the relevant pathway in healthy volunteers. However, scopolamine metabolism in man has not been verified stringently. An elucidation of the chemical structures of the metabolites extracted from human urine is still lacking. Scopolamine has been shown to undergo an oxidative demethylation during incubation with CYP3A (cytochrome P-450 subfamily). To inhibit the CYP3A located in the intestinal mucosa, components of grapefruit juice are very suitable. When scopolamine was administered together with 150 mL grapefruit juice, the alkaloid concentrations continued to increase, resulting in an evident prolongation of tmax (59.5 +/- 25.0 minutes; P < 0.001). The AUC0-24h values of scopolamine were higher during the grapefruit juice period. They reached approximately 142% of the values associated with the control group (P < 0.005). Consequently, the related absolute bioavailabilities (range 6% to 37%) were significantly higher than the corresponding values of the drug orally administered together with water (range 3% to 27%). The effect of the alkaloid on quantitative electroencephalogram (qEEG) and cognitive performance correlated with pharmacokinetics was shown in studies with healthy volunteers. From pharmacokinetic-pharmacodynamic modeling techniques, a direct correlation between serum concentrations of scopolamine and changes in total power in alpha-frequency band (EEG) in healthy volunteers was provided. The alkaloid readily crosses the placenta. Therefore, scopolamine should be administered to pregnant women only under observation. The drug is compatible with nursing and is considered to be nonteratogenic. In conclusion, scopolamine is used for premedication in anesthesia and for the prevention of nausea and vomiting associated with motion sickness. Pharmacokinetics and pharmacodynamics of scopolamine depend on the dosage form. Effects on different cognitive functions have been extensively documented.

Gender differences in the pharmacokinetics of DA-6034, a derivative of flavonoids, in rats

Gender differences in the pharmacokinetics of DA-6034 were evaluated after intravenous and oral administration at a dose of 50 mg/kg to male and female Sprague-Dawley rats. After intravenous administration to male rats, although the total area under the plasma concentration-time curve from time zero to time infinity of DA-6034 was not significantly different between male and female rats, the plasma concentrations of DA-6034 were lower from 30 min to 480 min, the mean residence time was significantly shorter (6.28 versus 12.2 min), the percentage of intravenous dose of DA-6034 excreted in 24 h urine as unchanged drug was significantly greater (14.4% versus 10.5% of intravenous dose). After oral administration, the pharmacokinetic parameters of DA-6034 were not significantly different between male and female rats.

Female-specific aspects in the pharmacotherapy of chronic cardiovascular diseases

Differences in pharmacokinetics, pharmacodynamics, and physiology contribute to the phenomenon that women and men frequently respond differently to cardiovascular drugs. Hormonal influences, in addition, can play an important role: for example, the menstrual cycle, menopause, and pregnancy--as a result of fluctuations in concentrations of sexual steroids, and of changes in total body water--can be associated with gender-specific differences in the plasma levels of cardiovascular drugs. Clinical relevance accordingly results, especially for substances with a narrow therapeutic margin. This review treats the most important pharmacodynamic gender-relevant differences in this context, and surveys available evidence on the benefits of therapy of chronic cardiovascular diseases in women. On the whole, the study situation for women is appreciably less favourable than for men: owing to the fact that women are under-represented in most studies, and that few gender-specific analyses have been conducted.

Assessment of sex differences in pharmacokinetics and pharmacodynamics of amlodipine in a bioequivalence study

AIMS

This study was conducted to assess the bioequivalence between two 10-mg amlodipine tablet formulations. As secondary objectives, sex-related differences and tolerability profile were evaluated.

METHODS

Thirty-six healthy volunteers (18 males and 18 females; age 20-32 years, weight 49.5-98.0 kg) were included in a randomised crossover study. Subjects were administered a single 10-mg oral dose of each formulation separated by a 14-day washout period. Plasma amlodipine levels were determined by a high performance liquid chromatographic method with tandem mass spectrometry detection.

RESULTS

All subjects completed the study and 90% confidence intervals for relevant pharmacokinetic parameters were within the ranges defined by European and US Regulatory Authorities: the geometric mean and the 90% confidence interval test/reference ratios calculated from log-transformed values were 104.54 (101.46-107.72%) for AUC(0-infinity) and 100.32 (97.41-103.33%) for Cmax. There were no serious or severe adverse events. The tolerability profile appeared to be comparable for the two products. On average, bioavailability of amlodipine was slightly higher in females than in males, but these differences could be explained by the lower body weight of women. There were no sex-related differences in drug clearance. Bioequivalence was also demonstrated within each gender group. Amlodipine treatment produced a slight decrease of systolic blood pressure and an increased in heart rate, which were more pronounced in women. The incidence of adverse events was similar in men and women.

CONCLUSIONS

The two formulations were considered bioequivalent. Although there were no relevant gender-related differences in the pharmacokinetics of amlodipine, women reached higher amlodipine concentrations most likely because of their lower body weight, and therefore, the reported pharmacodynamic effects were higher within this gender group.

Gender differences in pharmacokinetics of oral warfarin in rats

Gender different pharmacokinetics of warfarin were investigated after oral administration at a dose of 2 mg/kg to male and female rats. The concentrations of warfarin in rat plasma were analysed by the HPLC method. Noncompartmental analysis was used for the calculation of the total area under the plasma concentration-time curve from time zero to time infinity (AUC) and terminal half-life of warfarin. After oral administration of warfarin to female rats, the AUC was significantly greater (345 compared with 180 microg h/ml) than that in male rats.

Sex-related differences in the pharmacokinetics of oral ciprofloxacin

The oral pharmacokinetics of ciprofloxacin were studied in healthy volunteers to assess the influence of sex on its disposition. Subjects (8 males, 7 females) received a single oral dose of ciprofloxacin 750 mg, blood and urine samples were collected, and ciprofloxacin concentrations were determined. A two-compartment open-model with two or three absorption phases, each one having a fitted independent lag time, best fit the data using a weighted least squares estimator. Univariate and multivariate regression analyses were performed to determine the influence of renal function, weight, and subject sex on the oral clearance (CL(S)/F) and apparent steady-state volume of distribution (V(ss)/F) of ciprofloxacin. Females had a median C(max) of ciprofloxacin that was 30% greater than males and a significantly smaller median (range) V(ss)/F: 81.1 (44.8-111.6) versus 170.9 (140.9-213.4), respectively (p < 0.01). In addition, females had increased exposure to ciprofloxacin, with a slower median (range) CL(S)/F of 28.3 L/h (24.5-33.4) compared to 44.4 L/h (41.4-53.7) for males (p < 0.01). Regression analyses revealed that subject sex was the only significant predictor of CL(S)/F (p < 0.001), but both body weight (p = 0.04) and subject sex (p < 0.005) were significant predictors of V(ss)/F. Fixed oral doses of ciprofloxacin will lead to higher maximum concentration and total drug exposure in females compared to males and do not appear to be solely related to weight-based differences.

Lack of gender effect on the pharmacokinetics and pharmacodynamics of dexamethasone in the camel after intravenous administration

The pharmacokinetics and pharmacodynamics of dexamethasone were studied in six male and six female camels after a single intravenous dose (0.05 mgkg(-1) body weight) of dexamethasone. The pharmacokinetic parameters of the two-compartment pharmacokinetic model for female and male camels, respectively (mean+/-SEM) were as follows: terminal elimination half-lives were 8.02+/-1.15 and 7.33+/-0.80 h, total body clearances were 95.5+/-16.0 and 124.5+/-11.9 ml h(-1) per kg, volumes of distribution at steady state were 0.72+/-0.08 and 0.87+/-0.14 litre kg(-1), and the volumes of the central compartment were 0.12+/-0.02 and 0.17+/-0.02 litre kg(-1). There was no significant difference in any pharmacokinetic parameter between female and male camels. Pharmacodynamic effects were evaluated by measuring endogenous plasma cortisol, circulating lymphocytes and neutrophils numbers and were analysed using indirect pharmacokinetic/pharmacodynamic models. The estimated IC50 of dexamethasone for cortisol and lymphocytes for female and male camels were 3.74+/-0.99 and 2.28+/-1.09 and 2.63+/-0.71 and 2.41+/-0.79 ng ml(-1), respectively. The EC50 for neutrophils for female and male camels were 24.5+/-5.83 and 20.2+/-3.82 ng ml(-1), respectively. There was no significant difference in any pharmacodynamic parameter between female and male camels. Dexamethasone in urine could be detected for 4-5 days by enzyme-linked immunosorbent assay and for 3-4 days by liquid chromatography/mass spectrometry after an intravenous dose of 0.05 mg kg(-1) body weight.

Rodent nutritional model of non-alcoholic steatohepatitis: species, strain and sex difference studies

BACKGROUND AND AIM

The methionine choline-deficient (MCD) diet leads to steatohepatitis in rodents. The aim of the present study was to investigate species, strain and sex differences in this nutritional model of non-alcoholic steatohepatitis (NASH).

METHODS

Male and female Wistar, Long-Evans and Sprague-Dawley rats, and C57/BL6 mice (n = 6 per group) were fed a MCD diet for 4 weeks. Control groups received an identical diet supplemented with choline bitartrate (0.2% w/w) and methionine (0.3% w/w). Liver pathology (steatosis and inflammation) and ultrastructure, liver lipid profile (total lipids, triglycerides, lipid peroxidation products), liver : body mass ratios and serum alanine aminotransferase (ALT) levels were compared between these groups.

RESULTS

The MCD diet-fed male rats developed greater steatosis (P < 0.001), had higher liver lipid content (P < 0.05) and had higher serum ALT levels (P < 0.005) than did female rats. Wistar rats (both sexes) had higher liver lipid levels (P < 0.05), serum ALT levels (P < 0.05), and liver mass : body mass ratios (P < 0.025) than did Long-Evans and Sprague-Dawley rats. In female groups, Wistar rats showed greater fatty change than did the other two strains (P < 0.05). All rats fed the MCD diet developed hepatic steatosis, but necrosis and inflammation were minor features and fibrosis was absent. Compared with Wistar rats, male C57/BL6 mice showed a marked increase in inflammatory foci (P < 0.001), end products of lipid peroxidation (free thiobarbituric acid reactive substances) (P < 0.005), and mitochondrial injury, while showing less steatosis (P < 0.005), lower hepatic triglyceride levels, (P < 0.005) and lower early lipid peroxidation products (conjugated dienes and lipid hydroperoxides; P < 0.005 and P < 0.01, respectively).

CONCLUSIONS

The Wistar strain and the male sex are associated with the greatest degree of steatosis in rats subjected to the MCD diet. Of the groups studied, male C57/BL6 mice develop the most inflammation and necrosis, lipid peroxidation, and ultrastructural injury, and best approximate the histological features of NASH.

Gender-specific implications for cardiovascular medication use in the elderly optimizing therapy for older women

Sex should be considered during the selection of cardiovascular medications and dosages of cardiovascular medications. There is mounting evidence that clinically important differences between the sexes exist in the pharmacokinetic processes that determine drug concentrations and in the pharmacodynamic processes that determine physiologic responses to pharmacologic agents. Although aging also affects these processes, aging does not eliminate the sex-related differences. The major pharmacokinetic differences between the sexes, on average, are lower weight and distribution volumes in women compared with men and lower renal drug clearance in women compared with men. Sex-related differences in hepatic drug clearance are less predictable. Pharmacodynamic responses that differ between the sexes include increased adverse cardiovascular drug effects in women compared with men (torsade de pointes arrhythmias, increased risk of hemorrhagic consequences of anticoagulation or thrombolytic therapy, electrolyte abnormalities with diuretics, myopathy with HMG Co-A reductase inhibitors, cough with ACE inhibitors, and increased incidence of thrombosis). Recommendations for optimizing cardiovascular drug therapy for the older women include individualization of drug selection to minimize the number of medications and side effects; dosage adjustment based on age, size, and sex; close monitoring for side effects; and consideration of cost and access to medications. Optimal care for the older woman with cardiovascular disease will also require investigation of cardiovascular medications in older women and of therapies for cardiovascular diseases that are more common in women than men.

The influence of sex on pharmacokinetics

Biologic differences exist between men and women that can result in differences in responses to drugs. Both pharmacokinetic and pharmacodynamic differences between the sexes exist, with more data on pharmacokinetic differences. On average, men are larger than women. Body size differences results in larger distribution volumes and faster total clearance of most medications in men compared to women. Greater body fat in women (until older ages) may increase distribution volumes for lipophilic drugs in women. Total drug absorption does not appear to be significantly affected by sex although absorption rates may be slightly slower in women. Bioavailability after oral drug dosing, for CYP3A substrates in particular, may be somewhat higher in women compared to men. Bioavailability after transdermal drug administration does not appear to be significantly affected by gender; nor does protein binding. Renal processes of glomerular filtration, tubular secretion, and tubular reabsorption appear to be faster in men compared to women whether considered on a mg/kg basis or total body weight basis. Algorithms to estimate glomerular filtration rate incorporate sex as a factor; some also include weight. For hepatic processes, drugs metabolized by Phase I metabolism (oxidation, reduction, and hydrolysis via cytochrome P450's 1A, 2D6, 2E1), Phase II conjugative metabolism (glucuronidation, conjugation, glucuronyltransferases, methyltransferases, dehydrogenases) and by combined oxidative and conjugation processes are usually cleared faster in men compared to women (mg/kg basis). Metabolism by CYP2C9, CYP2C19, and N-acetyltransferase, appear to be similar in men and women (mg/kg). Clearance of p-glycoprotein substrates appear to be similar in men and women. In contrast, total clearance of a number of CYP3A substrates appear to be mildly or moderately faster (mg/kg) in women compared to men. The clinical significance of reported differences warrants consideration. Clearance reported on a per kg basis directly addresses organ or enzyme clearance. The difference in size between men and women means translating these results to clinical dosage rates should include an adjustment for body size. Unfortunately, this is not standard. Reports of sex differences that persist after considering weight may warrant further dosage adjustments. In addition, investigations are often performed in healthy fasting individuals yet medications are prescribed to patients with confounding influences of disease, co-medications, diet, and social habits. The relative role of sex on pharmacokinetics as compared to genetics, age, disease, social habits and their potential interactions in the clinical setting is not yet fully known but should be routinely considered and further studied.

Gender differences in drug effects: implications for anesthesiologists

BACKGROUND

The gender aspect in pharmacokinetics and pharmacodynamics of anesthetics has attracted little attention. Knowledge of previous work is required to decide if gender-based differences in clinical practice is justified, and to determine the need for research.

METHODS

Basis for this paper was obtained by Medline searches using the key words 'human' and 'gender' or 'sex,' combined with individual drug names. The reference lists of these papers were further checked for other relevant studies.

RESULTS

Females have 20-30% greater sensitivity to the muscle relaxant effects of vecuronium, pancuronium and rocuronium. When rapid onset of or short duration of action is very important, gender-modified dosing may be considered. Males are more sensitive than females to propofol. It may therefore be necessary to decrease the propofol dose by 30-40% in males compared with females in order to achieve similar recovery times. Females are more sensitive than males to opioid receptor agonists, as shown for morphine as well as for a number of kappa (OP2) receptor agonists. On this basis, males will be expected to require 30-40% higher doses of opioid analgesics than females to achieve similar pain relief. On the other hand, females may experience respiratory depression and other adverse effects more easily if they are given the same doses as males.

CONCLUSION

These examples illustrate that gender should be taken into account as a factor that may be predictive for the dosage of several anesthetic drugs. Moreover, there is an obvious need for more research in this area in order to further optimize drug treatment in anesthesia.

Pharmacokinetics of phenylbutazone in beef steers

Phenylbutazone was administered intravenously to a group of 11 beef steers at a dosage of 6 mg/kg of body weight. Whole plasma and protein-free plasma were analyzed for phenylbutazone residues. Pharmacokinetic parameters of total and free phenylbutazone in plasma were calculated using a noncompartmental method. In regards to whole plasma data, the mean volume of distribution at steady state (Vss), was 140 mL/kg body weight, with a mean (+/-SEM) terminal elimination half-life (t1/2) of 34 +/- 9 h. The mean clearance was 3.2 mL/h/kg body weight. The Vss, as determined from the protein-free plasma fraction, was 54093 mL/kg body weight. This larger Vss of free phenylbutazone compared with total plasma phenylbutazone was attributed to a high degree of plasma protein binding, as well as the greater penetration of free phenylbutazone into tissues. The mean t1/2 of free phenylbutazone was 35 +/- 12 h. This similarity to the t1/2 estimated from total plasma phenylbutazone data is attributed to an equilibrium between free and plasma phenylbutazone during the terminal elimination phase. The pharmacokinetic parameters of free and total plasma phenylbutazone in beef steers are statistically similar to those previously reported for lactating dairy cows.

Differential gene expression of organic anion transporters in male and female rats

Sex-related differential gene expression of organic anion transporters (rOAT1, rOAT2, and rOAT3) in rat brain, liver, and kidney was investigated. There were no sex differences in the expression of rOAT1 mRNA. rOAT2 mRNA was abundant in the liver and weakly expressed in the kidney of male rats; however, the OAT2 gene was strongly expressed in both organs of females. The abundance of rOAT2 mRNA markedly increased in castrated male rat kidney; however, treatment of castrated male rats with testosterone led to a decrease of rOAT2 mRNA. Expression of rOAT3 mRNA in intact female rats was found in the kidney and brain, whereas in males rOAT3 mRNA was also found in the liver. rOAT3 mRNA markedly decreased in the liver of castrated male rats but increased in testosterone-treated castrated male rats. Moreover, rOAT3 mRNA increased in the hypophysectomized female rat liver, indicating that rOAT3 is an inducible isoform. The present findings suggest that sex steroids play an important role in the expression and maintenance of OAT2/3 isoforms in the rat liver and kidney. Our results provide information on the differential gene expression of OAT isoforms with sex hormone dependency.

Gender-based differences in the toxicity of pharmaceuticals--the Food and Drug Administration's perspective

Women experience more adverse reactions to treatment with therapeutic drugs than men. Theories proposed to explain this include overdosing, different pharmacokinetics and pharmacodynamics, women are more likely to report adverse events than men, or women take more medications than men. Food and Drug Administration (FDA) Office of Women's Health (OWH) funds research to promote including women in clinical trials and understanding the biology of sex-related differences in the safety of FDA-regulated products. Including women in clinical trials advances the understanding of drug efficacy and safety in women by providing information on drug dosing, pharmacokinetics, and pharmacodynamics. A Baysian statistical analysis of sex differences in adverse events showed that although about the same number of adverse events were reported for men and women, those reported for women were more serious. One example of a sex difference in the toxicity of pharmaceuticals is the drug-induced cardiac arrhythmia, torsades de point. OWH funded studies in animals and humans to investigate the mechanism behind this sex difference. These studies demonstrated that shortening the QT interval increases the risk of developing torsades and that androgens protect against torsades by slowing cardiac repolarization and prolonging the QT interval. Understanding the mechanisms behind other reported sex-related differences in adverse drug effects requires additional research. The preliminary studies conducted to date suggest that this sex-related difference is likely to be a multifactorial problem requiring information from several fields of study. Ideally, individuals at risk for developing an adverse event should be identified prior to therapeutic intervention. The OWH plans to fund more studies to investigate the role of hormonal variations on drug metabolism and drug-drug interactions. Animal and in vitro model systems are needed to fully understand the mechanism of how gender influences drug toxicity.

The effect of sex and age on caffeine pharmacokinetics in cattle

The aim of this study was to determine the effect of sex on the pharmacokinetics of caffeine in cattle at different ages. Ten female and 10 male Holstein cattle were subject to a caffeine test when they were aged 1, 2, 4, 6, 8, 12 and 18 months. Caffeine, 5 mg kg(-1)body weight, was given intravenously as a sterile isotonic solution. An automated, enzyme-multiplied, immunoassay technique (EMIT) was used to determine plasma caffeine concentration. The volume of distribution of caffeine (V(SS)) decreased significantly between 1 and 18 months of life. Mean V(SS)values observed in males and females were not statistically different. The experimental period was characterised by a steady decrease (statistically significant) in caffeine mean residence time (MRT). These values did not differ significantly between males and females under 8 months of age. In 8-, 12- and 18-month-old animals, the caffeine MRT in the females was significantly shorter than in the males. The total plasma clearance (Cl(tot)) of caffeine increased significantly between 1 and 18 months of age. No significant differences were observed between total plasma clearance of caffeine in males and females under 8 months of age. In 8-, 12- and 18-month-old animals, the Cl(tot)of caffeine was significantly higher in females than in males. In conclusion, we report a sex-linked difference in pharmacokinetics of caffeine in cattle over 8 months of age, the females being the more active metabolisers. The results of the present study support the hypothesis that the metabolism of xenobiotics is sexually different in ruminants.

Gender-specific effects on verapamil pharmacokinetics and pharmacodynamics in humans

Pharmacokinetic studies of i.v. and oral racemic verapamil and 14C-erythromycin breath tests (ERBT) were performed in 84 healthy men (n = 42) and women (n = 42). Verapamil was measured by HPLC, concentration versus time data were analyzed by noncompartmental models, protein binding was measured by equilibrium dialysis, and statistical analyses were performed by ANOVA. Clearance of i.v. and p.o. verapamil was 13.7 +/- 4.3 and 58.4 +/- 35 ml/min/kg (mean +/- SD) in women compared to 12.6 +/- 3.4 and 82.6 +/- 70 ml/min/kg in men (p = 0.076). Bioavailability was higher in women (0.25 +/- 0.09) compared to men (0.20 +/- 0.09, p = 0.019) with a significant Gender x Formulation interaction (p = 0.04). ERBT were higher in women (p < 0.0001). Verapamil (i.v. and p.o.) decreased blood pressure in all subjects with greater heart rate increases after p.o. verapamil in women compared to men (p = 0.041). The findings suggest that sex-specific differences in drug metabolism may occur in both the gut and the liver and involve multiple metabolic pathways and that pharmacokinetic differences will alter pharmacodynamic responses.

Pharmacokinetic changes of theophylline and amikacin through the menstrual cycle in healthy women

The objective of this open-label, single-dose study was to clarify the influence of the menstrual cycle on the pharmacokinetics of theophylline (n = 10) and amikacin (n = 8) in young healthy Japanese women with regular menstrual cycles. Each subject received an intravenous infusion of theophylline or amikacin sulfate at four different phases--mid-follicular (phase I), peri-ovulatory (phase II), mid-luteal (phase III), and premenstrual days (phase IV). In the theophylline study, there were no significant differences in the pharmacokinetic parameters among the four phases studied. In the amikacin study, CLtot was 15% higher in phase III than in phase I (p < 0.01). Vd beta was 35% higher in phase III than in phase I (p < 0.05). The other pharmacokinetic parameters of amikacin were not significantly altered during the menstrual cycle. Evidence suggests that the phase of the menstrual cycle may be a factor in determining the pharmacokinetics of amikacin.

Gender-related differences in pharmacokinetics and their clinical significance

In this review I have attempted to summarize gender differences in pharmacokinetics involving the cytochrome P450 (CYP) isozymes of young and mature adults, excluding the effects of the menstrual cycle, use of oral contraceptives and pregnancy. Sex differences in drug metabolism and elimination are mainly related to steroid hormone levels. CYP3A4, responsible for the metabolism of over 50% of therapeutic drugs, exhibits higher activity in women than in men. Nonetheless, the absence of a sex difference has been reported by some workers. The activity of several other CYP (CYP2C19, CYP2D6, CYP2E1) isozymes and the conjugation (glucuronidation) activity involved in drug metabolism may be higher in men than in women. Drug metabolism in women is affected by sex-specific factors (menopause, pregnancy and menstruation) in addition to the cigarette smoking, drug ingestion and alcohol consumption that are more commonly observed factors in men. Furthermore, they are affected by physiological factors such as drug absorption, protein binding and elimination. Thus, careful attention should be paid to the side-effects and toxicity arising from sex differences in drug metabolism in clinical situations. Although there are specific ethical considerations regarding carrying out drug trials in women, the relationship between the side-effects and toxicity that may be influenced by hormones during drug metabolism and drug treatment needs further study.