Phenotypic polymorphism and gender-related differences of CYP1A2 activity in a Chinese population

Evaluation of gender differences in the pharmacokinetics of oral zileuton nanocrystalline formulation using a rat model

Zileuton is a leukotriene inhibitor used to treat asthma. As a BCS class II drug it exhibits challenges with solubility which likely impact its absorption. As patient gender significantly impacts the pharmacokinetics of many drugs, this study aimed to investigate potential gender-based pharmacokinetic differences after oral zileuton administration in rats. Male and female Sprague Dawley rats received single oral gavage doses of pure zileuton as an active pharmaceutical ingredient (30 mg/kg body weight (bw)), physical mixture (PM; at 30 mg/kg bw of the formulation contains zileuton, kollidon VA64 fine, dowfax2A1 and trehalose), and nanocrystalline formulation of zileuton (NfZ; at 30 mg/kg bw of the formulation). Plasma, tissue, and urine concentrations were quantified using high performance liquid chromatography (HPLC). Noncompartmental pharmacokinetic analysis showed higher zileuton levels in the plasma of female versus male rats across all evaluated forms of zileuton (API, PM, and NfZ). Female rats demonstrated higher peak plasma concentrations (Cmax) and increased area under the plasma concentration-time curve (AUC) relative to males, regardless of formulation. These findings reveal substantial gender disparities in the pharmacokinetics of zileuton in the rat model. This study emphasizes the critical need to evaluate gender differences during preclinical drug development to enable gender-based precision dosing strategies for equivalent efficacy/safety outcomes in male and female patients. Additional studies are warranted to investigate underlying mechanisms of such pharmacokinetic gender divergences.

Effect of Dietary Intake on the Pharmacokinetics of the Multitargeted Receptor Tyrosine Kinase Inhibitor Famitinib: Results From a Phase 1 Study in Healthy Chinese Participants

Famitinib is a tyrosine kinase inhibitor under clinical investigation for the treatment of solid tumors. Here, a 3-period crossover trial investigated the effect of high-fat or low-fat food intake on the single-dose pharmacokinetic properties of oral famitinib. Twenty-four healthy Chinese participants were enrolled and received a single 25-mg dose of famitinib malate capsule following a high-fat or low-fat breakfast before dosing. Blood samples were collected before dosing (0 hour) to 192 hours after dosing, and famitinib concentrations in plasma were determined with validated liquid chromatography-tandem mass spectrometry. Compared with the fasting condition, the geometric mean ratios for low-fat/fasting were 98.6%, 107.7%, and 107.5% for maximum plasma concentration, area under the plasma concentration-time curve (AUC) over the dosing interval, and AUC from time 0 to infinity, respectively. Those for high-fat/fasting were 84.4%, 105.0%, and 105.1% for maximum plasma concentration, AUC over the dosing interval, and AUC from time 0 to infinity, respectively. There was no significant difference in adverse events between fasting and fed conditions, and no serious adverse events occurred during the trial. In conclusion, oral famitinib bioavailability is not affected by food intake, implying that patients with cancer do not need to consider dietary status when using famitinib. This is considered important for convenience and treatment compliance.

Seeing what is behind the smokescreen: A systematic review of methodological aspects of smoking interaction studies over the last three decades and implications for future clinical trials

Smoking drug interaction studies represent a common approach for the clinical investigation of CYP1A2 induction. Despite this important role, they remain an "orphan topic" in the existing regulatory framework of drug interaction studies, and important methodological aspects remain unaddressed. The University of Washington Drug Interaction Database (DIDB) was used to systematically review the published literature on dedicated smoking pharmacokinetic interaction studies in healthy subjects (1990 to 2021, inclusive). Various methodological aspects of identified studies were reviewed. A total of 51 studies met all inclusion criteria and were included in the analysis. Our review revealed that methods applied in smoking interaction studies are heterogeneous and often fall short of established methodological standards of other interaction trials. Methodological deficiencies included incomplete description of study populations, poor definition and lack of objective confirmation of smoker and nonsmoker characteristics, under-representation of female subjects, small sample sizes, frequent lack of statistical sample size planning, frequent lack of use of existing markers of nicotine exposure and CYP1A2 activity measurements, and frequent lack of control of extrinsic CYP1A2 inducing or inhibiting factors. The frequent quality issues in the assessment and reporting of smoking interaction trials identified in this review call for a concerted effort in this area, if the results of these studies are meant to be followed by actionable decisions on dose optimization, when needed, for the effects of smoking on CYP1A2 victim drugs in smokers.

Sexual Dimorphism in the Expression of Cytochrome P450 Enzymes in Rat Heart, Liver, Kidney, Lung, Brain, and Small Intestine

Cytochrome P450 (P450) enzymes are monooxygenases that are expressed hepatically and extrahepatically and play an essential role in xenobiotic metabolism. Substantial scientific evidence indicates sex-specific differences between males and females in disease patterns and drug responses, which could be attributed, even partly, to differences in the expression and/or activity levels of P450 enzymes in different organs. In this study, we compared the mRNA and protein expression of P450 enzymes in different organs of male and female Sprague-Dawley rats by real-time polymerase chain reaction and western blot techniques. We found significant sex- and organ-specific differences in several enzymes. Hepatic Cyp2c11, Cyp2c13, and Cyp4a2 showed male-specific expression, whereas Cyp2c12 showed female-specific expression. Cyp2e1 and Cyp4f enzymes demonstrated higher expression in the female heart and kidneys compared with males; however, they showed no significant sexual dimorphism in the liver. Male rats showed higher hepatic and renal Cyp1b1 levels. All assessed enzymes were found in the liver, but some were not expressed in other organs. At the protein expression level, CYP1A2, CYP3A, and CYP4A1 demonstrated higher expression levels in the females in several organs, including the liver. Elucidating sex-specific differences in P450 enzyme levels could help better understand differences in disease pathogeneses and drug responses between males and females and thus improve treatment strategies. SIGNIFICANCE STATEMENT: This study characterized the differences in the mRNA and protein expression levels of different cytochrome P450 (P450) enzymes between male and female rats in the heart, liver, lung, kidney, brain, and small intestine. It demonstrated unique sex-specific differences in the different organs. This study is considered a big step towards elucidating sex-specific differences in P450 enzyme levels, which is largely important for achieving a better understanding of the differences between males and females in the disease's processes and treatment outcomes.

Cytochromes P450 and P-Glycoprotein Phenotypic Assessment to Optimize Psychotropic Pharmacotherapy: A Retrospective Analysis of Four Years of Practice in Psychiatry

Altered cytochromes P450 enzymes (CYP) and P-glycoprotein transporter (P-gp) activity may explain variabilities in drug response. In this study, we analyzed four years of phenotypic assessments of CYP/P-gp activities to optimize pharmacotherapy in psychiatry. A low-dose probe cocktail was administered to evaluate CYP1A2, 2B6, 2D6, 2C9, 2C19, 3A4, and P-gp activities using the probe/metabolite concentration ratio in blood or the AUC. A therapeutic adjustment was suggested depending on the phenotyping results. From January 2017 to June 2021, we performed 32 phenotypings, 10 for adverse drug reaction, 6 for non-response, and 16 for both reasons. Depending on the CYP/P-gp evaluated, only 23% to 56% of patients had normal activity. Activity was decreased in up to 57% and increased in up to 60% of cases, depending on the CYP/P-gp evaluated. In 11/32 cases (34%), the therapeutic problem was attributable to the patient's metabolic profile. In 10/32 cases (31%), phenotyping excluded the metabolic profile as the cause of the therapeutic problem. For all ten individuals for which we had follow-up information, phenotyping allowed us to clearly state or clearly exclude the metabolic profile as a possible cause of therapeutic failure. Among them, seven showed a clinical improvement after dosage adaptation, or drug or pharmacological class switching. Our study confirmed the interest of CYP and P-gp phenotyping for therapeutic optimization in psychiatry.

Effect of caffeine on muscle oxygen saturation during short-term all-out exercise: a double-blind randomized crossover study

PURPOSE

The ergogenic effect of oral caffeine administration on short-term all-out exercise performance is well established. However, the potential mechanisms associated with caffeine's ergogenicity in this type of exercise are poorly understood. The aim of this study was to investigate whether caffeine intake modifies muscle oxygen saturation during the 15-s Wingate Anaerobic Test.

METHODS

Fifteen moderately trained individuals (body mass = 67.4 ± 12.3 kg; height 171.3 ± 6.9 cm; age 31 ± 6 years) took part in two identical experimental trials after the ingestion of (a) 3 mg/kg of caffeine or (b) 3 mg/kg of cellulose (placebo). After 60 min for substances absorption, participants performed a 15-s Wingate test on a cycle ergometer against a load representing 7.5% of participant's body mass. Muscle oxygen saturation was continuously measured during exercise with near-infrared spectroscopy and blood lactate concentration was measured 1 min after exercise.

RESULTS

In comparison to the placebo, the oral administration of caffeine increased peak power by 2.9 ± 4.5% (from 9.65 ± 1.38 to. 9.92 ± 1.40 W/kg, P = 0.038; effect size (ES), 95% confidence intervals = 0.28, 0.05-0.51), mean power by 3.5 ± 6.2% (from 8.30 ± 1.08 to 8.57 ± 1.12 W/kg, P = 0.044; ES = 0.36, 0.01-0.71) and blood lactate concentration by 20.9 ± 24.7% (from 12.4 ± 2.6 to 14.8 ± 4.0 mmol/L, P = 0.005; ES = 0.59, 0.16-1.02). However, caffeine did not modify the curve of muscle oxygen desaturation during exercise (lowest value was 23.1 ± 14.1 and 23.4 ± 14.1%, P = 0.940).

CONCLUSION

Caffeine's ergogenic effect during short-term all-out exercise seems to be associated with an increased glycolytic metabolism with no influence of enhanced muscle oxygen saturation.

Evaluation of CYP1A2 activity: Relationship between the endogenous urinary 6-hydroxymelatonin to melatonin ratio and paraxanthine to caffeine ratio in dried blood spots

The suitability of the endogenous 6‐hydroxymelatonin/melatonin urinary metabolic ratio as a surrogate for the paraxanthine/caffeine ratio to predict cytochrome P450 1A2 (CYP1A2) activity was assessed in this study. Twelve healthy volunteers completed four study sessions spread over 1 month (including overnight urine collection with first morning voids collected separately). Except for the third session, volunteers were asked to abstain from methylxanthine‐containing beverages and foods at least 24 h before urine collection. At the end of urine collection, subjects were given a caffeinated beverage and capillary blood samples were collected 2 h after the drink administration. A significant linear relationship between the 6‐hydroxymelatonin/melatonin ratios from 12‐h urine samples and first morning voids was observed (R² = 0.876, p < 0.0001). In contrast to the paraxanthine/caffeine ratio, consumption of methylxanthine‐containing beverages during session three did not significantly influence the 6‐hydroxymelatonin/melatonin ratios compared with the other sessions requiring abstinence from caffeine. A larger intra‐ and interindividual variability in the 6‐hydroxymelatonin/melatonin ratios compared with the paraxanthine/caffeine ratio was also observed. A very weak correlation was observed between the paraxanthine/caffeine ratio and both of the endogenous 6‐hydroxymelatonin/melatonin ratios (Pearson r < 0.35, p < 0.05). All these results question whether this endogenous metric could adequately reflect CYP1A2 activity or substitute for the probe caffeine. Additional studies with larger study samples are needed to examine this endogenous metric in more details.

CYP1A2 mRNA Expression Rather than Genetic Variants Indicate Hepatic CYP1A2 Activity

CYP1A2, one of the most abundant hepatic cytochrome P450 enzymes, is involved in metabolism of several drugs and carcinogenic compounds. Data on the significance of CYP1A2 genetic polymorphisms in enzyme activity are highly inconsistent; therefore, the impact of CYP1A2 genetic variants (−3860G>A, −2467delT, −739T>G, −163C>A, 2159G>A) on mRNA expression and phenacetin O-dealkylation selective for CYP1A2 was investigated in human liver tissues and in psychiatric patients belonging to Caucasian populations. CYP1A2*1F, considered to be associated with high CYP1A2 inducibility, is generally identified by the presence of −163C>A polymorphism; however, we demonstrated that −163C>A existed in several haplotypes (CYP1A2*1F, CYP1A2*1L, CYP1A2*1M, CYP1A2*1V, CYP1A2*1W), and consequently, CYP1A2*1F was a much rarer allelic variant (0.4%) than reported in Caucasian populations. Of note, −163C>A polymorphism was found to result in an increase of neither mRNA nor the activity of CYP1A2. Moreover, hepatic CYP1A2 activity was associated with hepatic or leukocyte mRNA expression rather than genetic polymorphisms of CYP1A2. Consideration of non-genetic phenoconverting factors (co-medication with CYP1A2-specific inhibitors/inducers, tobacco smoking and non-specific factors, including amoxicillin+clavulanic acid therapy or chronic alcohol consumption) did not much improve genotype−phenotype estimation. In conclusion, CYP1A2-genotyping is inappropriate for the prediction of CYP1A2 function; however, CYP1A2 mRNA expression in leukocytes can inform about patients’ CYP1A2-metabolizing capacity.

Safety and efficacy of fluvoxamine in COVID-19 ICU patients: An open label, prospective cohort trial with matched controls

Aims

Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI) and sigma‐1 receptor agonist, has so far shown promise in the prevention of COVID‐19 progression as an early treatment option in three trials. The aim of this study was to evaluate the safety and efficacy of fluvoxamine in COVID‐19 patients if administered later in the course of the disease.

Methods

The study was designed as an open‐label, prospective cohort trial with matched controls. In April and May 2021, 51 ICU COVID‐19 patients hospitalised in the University Hospital Dubrava and University Hospital Centre Zagreb, Croatia, were treated with fluvoxamine 100 mg three times daily for 15 days in addition to standard therapy and they were prospectively matched for age, gender, vaccination against COVID‐19, disease severity and comorbidities with 51 ICU controls.

Results

No statistically significant differences between groups were observed regarding the number of days on ventilator support, duration of ICU or total hospital stay. However, overall mortality was lower in the fluvoxamine group, 58.8% (n = 30/51), than in the control group, 76.5% (n = 39/51), HR 0.58, 95% CI (0.36–0.94, P = .027).

Conclusion

Fluvoxamine treatment in addition to the standard therapy in hospitalised ICU COVID‐19 patients could have a positive impact on patient survival. Further studies on the effects of fluvoxamine in COVID‐19 patients are urgently required.

Pharmacokinetic Study of Frovatriptan Succinate Tablet After Single and Multiple Oral Doses in Chinese Healthy Subjects

Purpose

The present report describes findings from a Phase I clinical study that evaluated the single- and multiple-dose pharmacokinetics of frovatriptan succinate tablet in Chinese healthy subjects.

Methods

A total of 24 healthy subjects were enrolled. In single-dose study, 2.5, 5, and 10 mg oral doses of frovatriptan succinate tablet were administrated. A 2.5 mg frovatriptan succinate tablet was administrated 12 times in 7 days in the multiple-dose study. Blood samples were collected at scheduled time points.

Results

The results in single-dose study indicated that the blood levels were proportional to the administered dose, with the mean C_max and AUC_last ranging from approximately 6.27 ng/mL–17.35 ng/mL and 92.52 h⋅ng/mL – 287.40 h⋅ng/mL over the dose range. In the multiple-dose study, moderate drug accumulation was noted, which was attributable to forvatriptan’s long t_1/2 of about 26.47 to 30.63 h. Gender differences were noticed in both single- and multiple-dose study; exposure PK parameters were consistently higher in female than in male.

Conclusion

These pharmacokinetic evaluations in healthy Chinese subjects found that frovatriptan succinate tablet has an acceptable pharmacokinetic profile in Chinese subjects.

The increasing challenge of the possible impact of ethnicity on psychopharmacology

Ethnic differences may significantly influence the outcome of psychopharmacological treatment, in terms of prescription, adherence, clinical response, emergence of side effects, as well as pharmacokinetics and pharmacodynamics. The purpose of this review was to explore the available literature in order to provide general suggestions to help clinicians in choosing the best therapeutic option for patients, taking into account ethnicity. Although findings are sometimes controversial, the overall published studies suggest that ethnicities other than Caucasians tend to show a lower response to antidepressants and a reduced compliance. Africans tend to be more prescribed with antipsychotics, probably due to cultural stereotypes, except with clozapine, probably for their chronic benign neutropenia. Asians usually require less antipsychotic dosages than Caucasians. The differential response and side effect profile of antidepressants and antipsychotics have been related to individual intrinsic factors, to genetic make-up, but also to cultural and contextual variables. Interestingly, albeit limited data suggest ethnic-related genetic heterogeneity at the level of the serotonin transporters, the cytochromes and some neuroreceptors. Taken together, no conclusive findings are available about the role and impact of ethnicity in psychopharmacology. One of the main problems is that the majority of the studies in psychopharmacology have been conducted on Caucasians, so that there is an urgent need to have data in other populations. Furthermore, in the era of precision medicine, the role of ethnicity may be also supported by genetic analysis.

Similar ergogenic effect of caffeine on anaerobic performance in men and women athletes

PURPOSE

Caffeine is widely considered an ergogenic aid to increase anaerobic performance although most of this evidence is supported by investigations with only male samples. To date, it is unknown if the ergogenic effect of caffeine on anaerobic performance is of similar magnitude in men and women athletes. The aim of this study was to determine the magnitude of the ergogenic effect of caffeine on the Wingate test in men and women.

METHODS

In a double-blind, placebo-controlled, cross-over experimental trial, ten women athletes and ten men athletes performed a 15-s adapted version of the Wingate test after ingesting 3 mg of caffeine per kg of body mass or a placebo (cellulose).

RESULTS

In comparison to the performance obtained in the 15-s Wingate test with a placebo, caffeine increased peak power in men (9.9 ± 0.8 vs. 10.1 ± 0.8 W/kg, p < 0.01, d = 0.26) and in women (8.8 ± 0.9 vs. 9.1 ± 0.8 W/kg, p = 0.04, d = 0.30). Caffeine was also effective to increase the mean power in men (8.9 ± 0.7 vs. 9.0 ± 0.7 W/kg, p = 0.01, d = 0.21) and women (8.1 ± 0.7 vs. 8.3 ± 0.7 W/kg, p = 0.01, d = 0.27). The ergogenic effect of caffeine on the 15-s Wingate peak power (2.3 ± 3.2% in men and 3.2 ± 2.8% in women; p = 0.46) and mean power (2.0 ± 1.7% and 2.4 ± 2.3%, respectively; p = 0.93) was of similar magnitude in both sexes.

CONCLUSION

Acute ingestion of 3 mg kg^-1 of caffeine enhanced peak and mean cycling power during a 15-s adapted version of the Wingate test in men and women and the ergogenic effect was of similar magnitude in both sexes. This information suggests that both men and women athletes might obtain similar benefits from caffeine supplementation during anaerobic exercise.

Pharmacokinetics of exogenous melatonin in relation to formulation, and effects on sleep: A systematic review

There is conflicting evidence on the clinical efficacy of exogenous melatonin for the treatment of sleep disorders. This may be due to differences in the pharmacokinetic (PK) properties of melatonin formulations used in clinical trials. The aim of this systematic review was to understand the relationship between melatonin formulations and PK parameters and, where possible, the effects on sleep outcomes. To this purpose, we conducted a systematic review and nineteen papers were included. The studies included three melatonin transdermal formulation, thirteen oral formulations, one topical, two buccal, two intravenous and two nasogastric formulations. Seven studies investigated the effect of the melatonin formulation on sleep and six of them found a significant improvement in one or more sleep parameters. The potential for an improved controlled release formulation that delays maximum concentration (C_max) was identified. The different formulations and doses affect melatonin PK, suggesting that treatment efficacy maybe affected. Based on the current evidence, we are unable to provide recommendations of specific melatonin formulations and PK parameters for specific sleep disorders. Future studies should systematically investigate how different PK parameters of melatonin formulations affect efficacy treatment of sleep as well as circadian disorders.

Cytochrome P450 expression and regulation in the brain

The regulation of brain cytochrome P450 enzymes (CYPs) is different compared with respective hepatic enzymes. This may result from anatomical bases and physiological functions of the two organs. The brain is composed of a variety of functional structures built of different interconnected cell types endowed with specific receptors that receive various neuronal signals from other brain regions. Those signals activate transcription factors or alter functioning of enzyme proteins. Moreover, the blood-brain barrier (BBB) does not allow free penetration of all substances from the periphery into the brain. Differences in neurotransmitter signaling, availability to endogenous and exogenous active substances, and levels of transcription factors between neuronal and hepatic cells lead to differentiated expression and susceptibility to the regulation of CYP genes in the brain and liver. Herein, we briefly describe the CYP enzymes of CYP1-3 families, their distribution in the brain, and discuss brain-specific regulation of CYP genes. In parallel, a comparison to liver CYP regulation is presented. CYP enzymes play an essential role in maintaining the levels of bioactive molecules within normal ranges. These enzymes modulate the metabolism of endogenous neurochemicals, such as neurosteroids, dopamine, serotonin, melatonin, anandamide, and exogenous substances, including psychotropics, drugs of abuse, neurotoxins, and carcinogens. The role of these enzymes is not restricted to xenobiotic-induced neurotoxicity, but they are also involved in brain physiology. Therefore, it is crucial to recognize the function and regulation of CYP enzymes in the brain to build a foundation for future medicine and neuroprotection and for personalized treatment of brain diseases.

Drug-Drug Interactions Involving Intestinal and Hepatic CYP1A Enzymes

Cytochrome P450 (CYP) 1A enzymes are considerably expressed in the human intestine and liver and involved in the biotransformation of about 10% of marketed drugs. Despite this doubtless clinical relevance, CYP1A1 and CYP1A2 are still somewhat underestimated in terms of unwanted side effects and drug–drug interactions of their respective substrates. In contrast to this, many frequently prescribed drugs that are subjected to extensive CYP1A-mediated metabolism show a narrow therapeutic index and serious adverse drug reactions. Consequently, those drugs are vulnerable to any kind of inhibition or induction in the expression and function of CYP1A. However, available in vitro data are not necessarily predictive for the occurrence of clinically relevant drug–drug interactions. Thus, this review aims to provide an up-to-date summary on the expression, regulation, function, and drug–drug interactions of CYP1A enzymes in humans.

Negative Correlation Between Vitamin A and Positive Correlation Between Vitamin E and Inflammation Among Healthy Adults in Korea: Based on the Korea National Health and Nutrition Examination Survey (KNHANES) 2016-2018 7th Edition

PURPOSE

Vitamins exert its effect through different isoforms. The isoform conversion phases involved are affected outside factors. Here, we investigated the correlation between serum retinol, α-tocopherol, and serum inflammatory markers using stratified data acquired from 2016 to 2018 Korea National Health and Nutrition Examination Survey (KNHANES).

MATERIALS AND METHODS

This study was based on data acquired from the 7th edition (2016-2018) of the Korea National Health and Nutrition Examination Survey, consisting of survey data on smoking and alcohol drinking, serum retinol level, serum α-tocopherol level, high-sensitivity C-reactive protein (hs-CRP), and baseline characteristics.

RESULTS

There was a negative correlation between serum retinol and hs-CRP in alcohol drinking men. There was a negative correlation between serum retinol and hs-CRP in the alcohol-nonsmoking female group. There was a positive correlation between α-tocopherol and hs-CRP in the nonsmoking and alcohol-drinking group. There was a positive correlation between α-tocopherol and hs-CRP in the nonsmoking and alcohol-drinking female group. There was positive correlation between vitamin A and E and metabolic syndrome. The lowest vitamin A level was observed in subjects with all five metabolic syndrome criteria matched.

CONCLUSION

There was a negative correlation between serum retinol and hs-CRP and positive correlation between α-tocopherol and hs-CRP. Absorption and secretion of serum retinol are affected by inflammation status through retinol-binding protein. Alcohol acts as a competitive inhibitor of vitamin A oxidation through alcohol dehydrogenase and ALDH activity. Smoking causes inflammation and induces reactive oxygen species scavenging system and increases cytochrome p450 levels. These factors may have contributed to the observed findings. Metabolic syndrome subjects increased as the levels of vitamin A and vitamin E increased. Since obesity is inversely related to ALDH activity, we postulate that patients with metabolic syndrome may also have low ALDH activity, especially in the Asian population. Future studies are warranted to study the efficacy of ALDH or ALDH inducers in patients with vitamin A deficiency or metabolic syndrome.

Altered activity of xenobiotic detoxifying enzymes at menopause - A cross-sectional study

Xenobiotic metabolism at menopause is an under-investigated topic, albeit women spend one-third of their life in the postmenopausal period. The present study examined the effect of menopause on the in vivo activities of CYP1A2, CYP2A6, xanthine oxidase (XO) and N-acetyltransferase-2 (NAT2) xenobiotic metabolizing enzymes. Enzyme activity was determined in 152 non-smoking volunteers following oral intake of a single dose of 200 mg caffeine and subsequent determination of caffeine metabolite ratios (CMRs) in a 6-h urine sample as follows: CYP1A2: (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X) and NAT2: AFMU/(AFMU+1U+1X). CMRs among groups were analyzed using one-way ANOVA. Significantly lower CYP1A2 and higher CYP2A6 CMRs were observed in postmenopausal compared to premenopausal women and age-matched men. These changes could be attributed to menopause rather than chronological aging since an age-related effect was not observed in premenopausal women or men of any age group. XO CMRs were higher in postmenopausal women and men>50 compared to premenopausal women and men<50, respectively, suggesting an age-related increase in XO activity. No significant alterations were discerned in NAT2 CMRs, in either slow- or rapid-acetylators, indicating that menopause exerts minimal modulation of xenobiotics metabolized by this enzyme. This study provides evidence that the transition to menopause induces significant alterations in xenobiotic-metabolizing enzymes independent of chronological aging suggesting altered metabolism of pharmaceutical and environmental agents.

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.

Effects of short-term saffron (Crocus sativus L.) intake on the in vivo activities of xenobiotic metabolizing enzymes in healthy volunteers

Crocus sativus L., a perennial plant grown mainly around the Mediterranean and Iran, has many medicinal properties including anti-inflammatory, anti-depressive and cancer preventing properties. Aqueous herbal extracts may affect the activity of Phase I and II enzymes involved in xenobiotic metabolism. The present study was designed to determine whether C. sativus infusion alters the activity of CYP1A2, CYP2A6, XO and NAT2 enzymes in humans. Thirty-four healthy volunteers consumed infusion prepared from C. sativus stigmata for six days. Enzyme phenotyping was assessed in saliva and urine using caffeine metabolite ratios as follows: CYP1A2: 17X/137Χ (saliva) and CYP1A2: (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X) and NAT2: AFMU/(AFMU+1U+1X) (urine). Following C. sativus intake, CYP1A2 index was reduced by ∼13.7% in saliva (before: 0.51 ± 0.22, after: 0.44 ± 0.14; p = 0.002) and ∼6.0% in urine (before: 3.81 ± 1.20, after: 3.58 ± 0.92; p = 0.054). CYP1A2 index was significantly reduced only in males (saliva, before: 0.65 ± 0.22, after: 0.51 ± 0.16; p = 0.0001; urine, before: 4.53 ± 1.19, after: 4.03 ± 0.87; p = 0.017) suggesting sexual dimorphism in CYP1A2 inhibition. There was no effect of C. sativus intake on CYP2A6, XO or NAT2 indices. Short-term consumption of C. sativus infusion is unlikely to result in significant herb-drug interactions involving the enzymes studied, with the exception of potential herb-CYP1A2 substrate interaction in males.

Pharmacokinetics of serotonergic drugs: focus on OCD

INTRODUCTION

Although the treatment of obsessive-compulsive disorder (OCD), a common, chronic, and disabling psychiatric condition, has significantly improved in the last decades, with the demonstration of the specific effectiveness of serotonin reuptake inhibitors (SRIs), a large proportion of patients still show high relapse rates. In addition, pharmacological treatments should be maintained for years, so that the clinicians should take into account the pharmacokinetic changes in the long-term, which may be responsible for dangerous side effects or interactions. Areas covered: The aim of this paper was to review the literature on the pharmacokinetics of SSRIs and clomipramine, and on their pharmacokinetic parameters in OCD patients. Expert opinion: Although the literature on the pharmacokinetics of both clomipramine and SSRIs is consistent, data on pharmacokinetic parameters in OCD patients are very few. Given the impact of OCD, its chronicity requiring long-term treatments, together with the need to increase the clinical response rate, more studies in this field are urgently required.

Caffeinated and decaffeinated coffee consumption and risk of all-cause mortality: a dose-response meta-analysis of cohort studies

BACKGROUND

Previous meta-analysis showed an inverse association between coffee consumption and all-cause mortality. However, the relationship between caffeinated and decaffeinated coffee consumption and all-cause mortality is inconsistent. We aimed to identify and review the published evidence updating the association between coffee consumption and all-cause mortality and, furthermore, to investigate the association of caffeinated and decaffeinated coffee consumption and all-cause mortality.

METHODS

We systematically searched PubMed and Web of Science for studies published up to 9 November 2017. Cohort studies in which authors reported relative risks (RRs) of all-cause mortality for at least three levels of coffee consumption were eligible. Random-effects models were used to estimate the pooled RR of all-cause mortality with coffee consumption. Restricted cubic splines were used to model the dose-response association.

RESULTS

We included 21 cohort study articles (10 103 115 study participants and 240 303 deaths). We found a nonlinear association between coffee consumption and all-cause mortality (P_nonlinearity  < 0.001). Compared with no or rare coffee consumption, with a consumption of 3 cups day^-1 , the risk of all-cause mortality might reduce 13% (RR = 0.87; 95% confidence interval = 0.84-0.89).

CONCLUSIONS

The findings of the present study provide quantitative data suggesting that coffee consumption plays a role in reducing the risk of all-cause mortality. Similar inverse associations are found for caffeinated coffee and decaffeinated coffee.

The Influence of Caffeine Expectancies on Sport, Exercise, and Cognitive Performance

Caffeine (CAF) is widely consumed across sport and exercise for its reputed ergogenic properties, including central nervous stimulation and enhanced muscular force development. However, expectancy and the related psychological permutations that are associated with oral CAF ingestion are generally not considered in most experimental designs and these could be important in understanding if/how CAF elicits an ergogenic effect. The present paper reviews 17 intervention studies across sport, exercise, and cognitive performance. All explore CAF expectancies, in conjunction with/without CAF pharmacology. Thirteen out of 17 studies indicated expectancy effects of varying magnitudes across a range of exercise tasks and cognitive skills inclusive off but not limited to; endurance capacity, weightlifting performance, simple reaction time and memory. Factors, such as motivation, belief, and habitual CAF consumption habits influenced the response. In many instances, these effects were comparable to CAF pharmacology. Given these findings and the lack of consistency in the experimental design, future research acknowledging factors, such as habitual CAF consumption habits, habituated expectations, and the importance of subjective post-hoc analysis will help to advance knowledge within this area.

Population Pharmacokinetic and Exposure-dizziness Modeling for a Metabotropic Glutamate Receptor Subtype 5 Negative Allosteric Modulator in Major Depressive Disorder Patients

Dizziness, the most frequently observed adverse event in patients with major depressive disorder, was observed with basimglurant, a selective, orally active metabotropic glutamate receptor subtype 5 negative allosteric modulator. The potential relationship between dizziness and basimglurant exposure was explored. The pharmacokinetics of basimglurant was characterized with nonlinear mixed effects modeling using data from 288 trial participants enrolled in five clinical trials. The pharmacokinetics of basimglurant after daily oral administration of a modified release formulation was best described by a two-compartment disposition model with a transit compartment, lag time for the absorption, and first-order elimination. The largest covariate effects were the effect of smoking and male gender on apparent clearance followed by the effect of body weight on distribution volumes. Clearance was twofold higher in smokers and 40% higher in males. A logistic regression model showed a statistically significant correlation between basimglurant C_max and incidence of dizziness. An increased risk of dizziness is predicted with increasing doses.

Sex differences in the psychopharmacological treatment of depression

Although a number of studies have observed that females respond better to serotonergic antidepressants than males and that postmenopausal females have a diminished response to antidepressants compared with younger females, there are also studies that conflict with both of these findings, making any generalizations regarding sex differences difficult to make. Sex variance in antidepressant efficacy and pharmacokinetics profiles have been attributed to sex-based physiological differences, behavioral differences, related disorders, and sex-specific conditions, including pregnancy and menopause. This paper will review the history and current research on sex effects of antidepressant treatment.

Gender-based personalized pharmacotherapy: a systematic review

PURPOSE

In general, male and female are prescribed the same amount of dosage even if most of the cases female required less dosage than male. Physicians are often facing problem on appropriate drug dosing, efficient treatment, and drug safety for a female in general. To identify and synthesize evidence about the effectiveness of gender-based therapy; provide the information to patients, providers, and health system intervention to ensure safety treatment; and minimize adverse effects.

METHODS

We performed a systematic review to evaluate the effect of gender difference on pharmacotherapy. Published articles from January 1990 to December 2015 were identified using specific term in MEDLINE (PubMed), EMBASE, and the Cochrane library according to search strategies that strengthen the reporting of observational and clinical studies.

RESULTS

Twenty-six studies fulfilled the inclusion criteria for this systematic review, yielding a total of 6309 subjects. We observed that female generally has a lower the gastric emptying time, gastric PH, lean body mass, and higher plasma volume, BMI, body fat, as well as reduce hepatic clearance, difference in activity of Cytochrome P450 enzyme, and metabolize drugs at different rate compared with male. Other significant factors such as conjugation, protein binding, absorption, and the renal elimination could not be ignored. However, these differences can lead to adverse effects in female especially for the pregnant, post-menopausal, and elderly women.

CONCLUSION

This systematic review provides an evidence for the effectiveness of dosage difference to ensure safety and efficient treatment. Future studies on the current topic are, therefore, recommended to reduce the adverse effect of therapy.

In vitro analysis of factors influencing CYP1A2 expression as potential determinants of interindividual variation

Individual differences in drug metabolism contribute to interindividual variation that characterizes responses to drugs and risk in exposure to foreign chemicals. Large individual differences are found in expression levels of CYP1A2, a major drug-metabolizing enzyme. Underlying causes for this variation are not well understood. Several factors, including tobacco smoking, consumption of cruciferous vegetables, and sex, have been associated with modulating CYP1A2 expression. To understand factors regulating expression of CYP1A2 in establishing a causal relationship, this study examined effects of cigarette smoke condensate (CSC), indole-3-carbinol (I3C), and 17β-estradiol (estradiol) on CYP1A2 expression in in vitro systems using human liver and lung cells. Treatment with CSC (2-25 μg/mL) significantly increased levels of CYP1A2 in six cell lines examined, in a concentration- and time-dependent manner. Fold changes in expression levels relative to controls varied among cell lines. CYP1A2 enzymatic activity also increased with CSC exposure. Treatment of H1299 and HepB3 cells with dietary agent I3C (50 and 100 μmol/L) increased CYP1A2 expression. In human cell lines H1299 and H1395, treatment with estradiol (10 and 100 nmol/L) significantly reduced expression of CYP1A2. Using ChIP assays, effects of CSC on histone modifications were analyzed. Increases in H3K4me3 and H4K16ac were observed at several segments in the CYP1A2 gene, whereas H3K27me3 decreased, following CSC treatment. These results suggest that CYP1A2 expression is affected epigenetically by CSC. Additional studies will be needed to further establish regulatory mechanisms underlying effects of various environmental, dietary, and endogenous factors on CYP1A2 expression in better predicting individual variation.

Gender-Related Differences in the Expression of Organic Cation Transporter 2 and its Role in Urinary Excretion of Metformin in Rats

Organic cation transporter 2 (rOCT2) and multidrug and toxin extrusion protein 1 (rMATE1) are mainly expressed in rat renal proximal tubules and mediate urinary excretion of cationic drugs, such as metformin. Accumulated evidence indicated that renal rOCT2 expression in male rats is much higher than that of female rats. However, it is unclear whether the gender-related differences in rOCT2 expression between male and female rats can affect the urinary excretion of metformin. The aim of this study was to investigate the effect of gender on the pharmacokinetics of metformin and to clarify the effect of gender-related differences on renal rOCT2 expression and its role in urinary excretion of metformin. Renal rOCT2 levels, but not rOCT1 and rMATE1, were significantly lowered in female rats when compared to that of male rats (P < 0.01), while the pharmacokinetic parameters, i.e., AUC0→t, t 1/2, CL/F, and cumulative urinary excretion of metformin, did not show any significant differences between female and male rats following oral administration of metformin at l00 mg/kg (P > 0.05). However, when metformin was orally administered at the dose of 500 mg/kg, the cumulative urinary excretion and renal tissue-to-plasma concentration ratio of metformin in female rats (26,689 ± 1266 μg and 2.96 ± 0.47 mL/g, respectively) were markedly lowered compared to that of male rats (32,949 ± 1384 μg and 4.20 ± 0.31 mL/g, respectively), and the plasma concentration of metformin in female rats (55.9 ± 4.5 μg/mL) was significantly increased compared to that of male rats (43.5 ± 3.1 μg/mL) at 2 h after oral administration. These results indicated that effect of gender-related differences on renal rOCT2 expression indeed contributes to the decreased urinary excretion of metformin in female rats when metformin was administered at relatively high doses.

Pharmacokinetic considerations when prescribing in children

Before prescribing, the pediatrician typically considers recommended dosing guidelines and issues related to safety. Rarely does (s)he consider the impact of normal growth and development on drug disposition and by extension drug action. This paper reviews how the processes of absorption, distribution, metabolism and elimination differ between healthy children and adults and briefly discusses considerations for medication prescribing in children where these processes are altered secondary to comorbidities.

Second-Trimester Maternal Serum Paraxanthine, CYP1A2 Activity, and the Risk of Severe Preeclampsia

OBJECTIVE

To measure the association between second-trimester maternal caffeine intake and caffeine metabolism through the CYP1A2 system and the risk of subsequent severe preeclampsia.

METHODS

This was a nested case-control study of women who had undergone second-trimester screening for fetal aneuploidy and had banked serum available for analysis. The outcome of interest was severe preeclampsia, and exposures were serum paraxanthine (1,7-dimethylxanthine), measured through high-performance liquid chromatography, and CYP1A2 activity, assessed by paraxanthine/caffeine ratios.

RESULTS

We identified 51 cases of severe preeclampsia from our population of 3,992 women (1.3%), of whom 33 had sufficient serum for analysis. These were compared with 99 healthy women. Median paraxanthine concentrations were not significantly higher in women in the control group than women in the case group (96.4 ng/mL compared with 38.0 ng/mL, P=.12), and higher serum paraxanthine was not associated with lower odds of severe preeclampsia (odds ratio [OR] 0.72, confidence interval [CI] 0.48-1.08). However, we found a significantly higher paraxanthine/caffeine ratio in women in the control group than women in the case group (0.37 compared with 0.23, P=.02) and a decreased risk of preeclampsia per every log standard deviation increase in paraxanthine/caffeine ratio (OR 0.53, 95% CI 0.31-0.90).

CONCLUSION

Faster caffeine metabolism in the second trimester, assessed by paraxanthine/caffeine ratios, is associated with a reduced risk of subsequent severe preeclampsia.

LEVEL OF EVIDENCE

II.

Effects of notoginsenoside R1 on CYP1A2, CYP2C11, CYP2D1, and CYP3A1/2 activities in rats by cocktail probe drugs

CONTEXT

Notoginsenoside R1 (NGR1) is the main component with cardiovascular activity in Panax notoginseng (Burk.) F. H. Chen, an herbal medicine that is widely used to enhance blood circulation and dissipate blood stasis.

OBJECTIVE

The objective of this study is to investigate NGR1's effects on CYP1A2, CYP2C11, CYP2D1, and CYP3A1/2 activities in rats in vivo through the use of the Cytochrome P450 (CYP450) probe drugs.

MATERIALS AND METHODS

After pretreatment with NGR1 or physiological saline, the rats were administered intraperitoneally with a mixture solution of cocktail probe drugs containing caffeine (10 mg/kg), tolbutamide (15 mg/kg), metoprolol (20 mg/kg), and dapsone (10 mg/kg). The bloods were then collected at a set of time-points for the ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) analysis.

RESULTS

NGR1 was shown to exhibit an inhibitory effect on CYP1A2 by increased caffeine Cmax (43.13%, p < 0.01) and AUC0 - ∞ (40.57%, p < 0.01), and decreased CL/F (62.16%, p < 0.01) in the NGR1-treated group compared with those of the control group, but no significant changes in pharmacokinetic parameters of tolbutamide, metoprolol, and dapsone were observed between the two groups, indicating that NGR1 had no effects on rat CYP2C11, CYP2D1, and CYP3A1/2.

DISCUSSION AND CONCLUSION

When NGR1 is co-administered with drugs that are metabolized by CYP1A2, the pertinent potential herb-drug interactions should be monitored.

Levels of caffeine and its metabolites among U.S. smokers and nonsmokers

Data from National Health and Nutrition Examination Survey for the years 2009-2010 were used to estimate the levels of caffeine and 14 of its metabolite among U.S. smokers and nonsmokers after adjustments were made for other factors that affect observed caffeine levels. In this study, when adjusted for daily caffeine intake, adjusted levels (AGM) of caffeine and its metabolites were not found to be statistically significantly different between smokers and nonsmokers. AGMs for caffeine and all of its metabolites were found to be statistically significantly higher (p < 0.01) among females aged ≥ 12 years than males. For caffeine, 1,3-dimethylxanthine, and 1,7-dimethylxanthine, those aged ≥ 20 years had statistically significantly higher (p < 0.01) AGM than those aged 12-19 years but the reverse was true for 7-methylxanthine and 3,7-dimethylxanthine (p ≤ 0.02). The order of the AGMs by race/ethnicity was non-Hispanic whites > Hispanics > non-Hispanic blacks and most of the differences were statistically significant, at least between non-Hispanic whites and non-Hispanic blacks (p < 0.01). In general, there was a statistically significant positive association between the levels of caffeine and its metabolites and body mass index as well as daily caffeine intake. However, the levels of 7-methylxanthine were negatively associated with body mass index.

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.

CYP1A2 polymorphism and theophylline clearance in Korean non-smoking asthmatics

Background

Theophylline is mainly metabolized by cytochrome P450 (CYP) 1A2 and CYP2E1 which show inter-individual variations. However, the underlying mechanism remains unknown in humans. We investigated the relationship between differences in theophylline clearance and genetic polymorphisms in the CYP1A2 and CYP2E1 gene in 89 Korean asthmatic patients.

Methods

Polymerase chain reaction (PCR) was performed on the 5'-flanking region of those genes. PCR products were directly sequenced and confirmed using the SNaP shot method. We determined whether the detected SNPs affected gene transcription using electrophoretic mobility shift assay (EMSA). Theophylline clearance (mL/kg/h) was assessed by using a Bayesian approach.

Results

Genetic polymorphisms were identified at 7 sites in the CYP1A2 gene and at 10 sites in the CYP2E1. Among them, subjects with genotypes (GA+AA) of the -3860G>A polymorphism were found to show higher theophylline clearance than those with genotypes GG (29.11 ± 0.91 mL/kg/h vs. 26.12 ± 0.80 mL/kg/h, p = 0.014). This polymorphic site was revealed to be a protein binding site by conducting EMSA on nuclear hepatocyte extracts.

Conclusion

In conclusion, increased theophylline clearance was significantly related to the -3860G>A polymorphism, which could be associated with increased CYP1A2 inducibility in Korean non-smoking asthmatics.

Applications of CYP450 testing in the clinical setting

Interindividual variability in drug response is a major clinical problem. Polymedication and genetic polymorphisms modulating drug-metabolising enzyme activities (cytochromes P450, CYP) are identified sources of variability in drug responses. We present here the relevant data on the clinical impact of the major CYP polymorphisms (CYP2D6, CYP2C19 and CYP2C9) on drug therapy where genotyping and phenotyping may be considered, and the guidelines developed when available. CYP2D6 is responsible for the oxidative metabolism of up to 25% of commonly prescribed drugs such as antidepressants, antipsychotics, opioids, antiarrythmics and tamoxifen. The ultrarapid metaboliser (UM) phenotype is recognised as a cause of therapeutic inefficacy of antidepressant, whereas an increased risk of toxicity has been reported in poor metabolisers (PMs) with several psychotropics (desipramine, venlafaxine, amitriptyline, haloperidol). CYP2D6 polymorphism influences the analgesic response to prodrug opioids (codeine, tramadol and oxycodone). In PMs for CYP2D6, reduced analgesic effects have been observed, whereas in UMs cases of life-threatening toxicity have been reported with tramadol and codeine. CYP2D6 PM phenotype has been associated with an increased risk of toxicity of metoprolol, timolol, carvedilol and propafenone. Although conflicting results have been reported regarding the association between CYP2D6 genotype and tamoxifen effects, CYP2D6 genotyping may be useful in selecting adjuvant hormonal therapy in postmenopausal women. CYP2C19 is responsible for metabolising clopidogrel, proton pump inhibitors (PPIs) and some antidepressants. Carriers of CYP2C19 variant alleles exhibit a reduced capacity to produce the active metabolite of clopidogrel, and are at increased risk of adverse cardiovascular events. For PPIs, it has been shown that the mean intragastric pH values and the Helicobacter pylori eradication rates were higher in carriers of CYP2C19 variant alleles. CYP2C19 is involved in the metabolism of several antidepressants. As a result of an increased risk of adverse effects in CYP2C19 PMs, dose reductions are recommended for some agents (imipramine, sertraline). CYP2C9 is responsible for metabolising vitamin K antagonists (VKAs), non-steroidal anti-inflammatory drugs (NSAIDs), sulfonylureas, angiotensin II receptor antagonists and phenytoin. For VKAs, CYP2C9 polymorphism has been associated with lower doses, longer time to reach treatment stability and higher frequencies of supratherapeutic international normalised ratios (INRs). Prescribing algorithms are available in order to adapt dosing to genotype. Although the existing data are controversial, some studies have suggested an increased risk of NSAID-associated gastrointestinal bleeding in carriers of CYP2C9 variant alleles. A relationship between CYP2C9 polymorphisms and the pharmacokinetics of sulfonylureas and angiotensin II receptor antagonists has also been observed. The clinical impact in terms of hypoglycaemia and blood pressure was, however, modest. Finally, homozygous and heterozygous carriers of CYP2C9 variant alleles require lower doses of phenytoin to reach therapeutic plasma concentrations, and are at increased risk of toxicity. New diagnostic techniques made safer and easier should allow quicker diagnosis of metabolic variations. Genotyping and phenotyping may therefore be considered where dosing guidelines according to CYP genotype have been published, and help identify the right molecule for the right patient.

Cytochrome P450 enzymes in drug metabolism: regulation of gene expression, enzyme activities, and impact of genetic variation

Cytochromes P450 (CYP) are a major source of variability in drug pharmacokinetics and response. Of 57 putatively functional human CYPs only about a dozen enzymes, belonging to the CYP1, 2, and 3 families, are responsible for the biotransformation of most foreign substances including 70-80% of all drugs in clinical use. The highest expressed forms in liver are CYPs 3A4, 2C9, 2C8, 2E1, and 1A2, while 2A6, 2D6, 2B6, 2C19 and 3A5 are less abundant and CYPs 2J2, 1A1, and 1B1 are mainly expressed extrahepatically. Expression of each CYP is influenced by a unique combination of mechanisms and factors including genetic polymorphisms, induction by xenobiotics, regulation by cytokines, hormones and during disease states, as well as sex, age, and others. Multiallelic genetic polymorphisms, which strongly depend on ethnicity, play a major role for the function of CYPs 2D6, 2C19, 2C9, 2B6, 3A5 and 2A6, and lead to distinct pharmacogenetic phenotypes termed as poor, intermediate, extensive, and ultrarapid metabolizers. For these CYPs, the evidence for clinical significance regarding adverse drug reactions (ADRs), drug efficacy and dose requirement is rapidly growing. Polymorphisms in CYPs 1A1, 1A2, 2C8, 2E1, 2J2, and 3A4 are generally less predictive, but new data on CYP3A4 show that predictive variants exist and that additional variants in regulatory genes or in NADPH:cytochrome P450 oxidoreductase (POR) can have an influence. Here we review the recent progress on drug metabolism activity profiles, interindividual variability and regulation of expression, and the functional and clinical impact of genetic variation in drug metabolizing P450s.

Bioequivalence and rapid absorption of zolmitriptan nasal spray compared with oral tablets in healthy Japanese subjects

BACKGROUND AND OBJECTIVE

Oral zolmitriptan is highly effective in the acute treatment of migraine. However, nausea and vomiting during attacks may limit the usefulness of oral medications. An alternative, nasal spray, formulation has been developed that demonstrates good efficacy, high tolerability and a very fast onset of action. This study assessed the pharmacokinetics and bioavailability of zolmitriptan and its active metabolite 183C91 in healthy Japanese subjects following single-dose (2.5 or 5mg) oral or intranasal administration.

METHODS

This was a single-centre, open-label, randomised, crossover study. Forty-eight subjects each received one oral and one intranasal dose of 2.5 or 5mg zolmitriptan, with a 72-hour washout period between doses. Blood was drawn at various timepoints from 2 minutes to 15 hours post-dose and urine was collected over the course of the study; samples were analysed for zolmitriptan and 183C91, from which pharmacokinetic parameters were calculated.

RESULTS

Zolmitriptan was detected in plasma 2 minutes after intranasal administration in the majority of subjects (~75%) compared with 10 minutes after oral administration. The intranasal : tablet ratio for zolmitriptan area under the concentration-time curve from time zero to infinity was 0.924 (90% CI 0.826, 1.033) and 0.960 (90% CI 0.865, 1.066) for the 2.5 and 5mg doses, respectively. Other pharmacokinetic parameters were similar between the two formulations. While 183C91 appeared in the plasma concurrently to zolmitriptan after oral dosing, its appearance was delayed to approximately 30 minutes after intranasal dosing. Zolmitriptan was safe and well tolerated at both doses.

CONCLUSIONS

The rapid absorption of zolmitriptan nasal spray may explain the faster relief from migraine reported in patients compared with oral zolmitriptan.

Sex-dependent modulation of treatment response

The response to a psychotropic medication reflects characteristics of both the medication and the substrate, ie, the individual receiving the medication. Sex is an individual characteristic that influences all elements of the pharmacokinetic process - absorption, distribution, metabolism, and elimination. The effects of sex on these components of the pharmacokinetic process often counterbalance one another to yield minimal or varying sexual differences in blood levels achieved. However, sex also appears to influence pharmacodynamics, the tissue response to a given level of medication. Consideration by the practitioner of sex as a possible contributing factor to treatment nonresponse will enhance the efficacy and precision of clinical interventions.

Metabolic capabilities of cytochrome P450 enzymes in Chinese liver microsomes compared with those in Caucasian liver microsomes

AIM

The most common causes of variability in drug response include differences in drug metabolism, especially when the hepatic cytochrome P450 (CYP) enzymes are involved. The current study was conducted to assess the differences in CYP activities in human liver microsomes (HLM) of Chinese or Caucasian origin.

METHODS

The metabolic capabilities of CYP enzymes in 30 Chinese liver microsomal samples were compared with those of 30 Caucasian samples utilizing enzyme kinetics. Phenacetin O-deethylation, coumarin 7-hydroxylation, bupropion hydroxylation, amodiaquine N-desethylation, diclofenac 4'-hydroxylation (S)-mephenytoin 4'-hydroxylation, dextromethorphan O-demethylation, chlorzoxazone 6-hydroxylation and midazolam 1'-hydroxylation/testosterone 6β-hydroxylation were used as probes for activities of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A, respectively. Mann-Whitney U test was used to assess the differences.

RESULTS

The samples of the two ethnic groups were not significantly different in cytochrome-b(5) concentrations but were significantly different in total CYP concentrations and NADPH-P450 reductase activity (P < 0.05). Significant ethnic differences in intrinsic clearance were observed for CYP1A2, CYP2C9, CYP2C19 and CYP2E1; the median values of the Chinese group were 54, 58, 26, and 35% of the corresponding values of the Caucasian group, respectively. These differences were associated with differences in Michaelis constant or maximum velocity. Despite negligible difference in intrinsic clearance, the Michaelis constant of CYP2B6 appeared to have a significant ethnic difference. No ethnic difference was observed for CYP2A6, CYP2C8, CYP2D6 and CYP3A.

CONCLUSIONS

These data extend our knowledge on the ethnic differences in CYP enzymes and will have implications for drug discovery and drug therapy for patients from different ethnic origins.