Polymorphisms in CYP1A1 and CYP3A5 Genes Contribute to the Variability in Granisetron Clearance and Exposure in Pregnant Women with Nausea and Vomiting

The safety of early pregnancy exposure to granisetron

OBJECTIVE

Current guidelines suggest that granisetron is an optional treatment for nausea and vomiting in pregnancy (NVP) despite lack of evidence to support fetal safety. We aimed to determine the association between early pregnancy exposure to granisetron and fetal/neonatal outcomes.

DESIGN

Medical records of patients treated for NVP during the first and second trimester between June 2013 to September 2015 were reviewed. Patients were asked to participate in the study by answering a detailed questionnaire regarding newborn's health and complementary data. Pregnancy outcomes of patients exposed to granisetron were compared with those of patients who were not exposed to granisetron.

RESULTS

100 Granisetron exposed pregnancies were compared with 108 granisetron unexposed pregnancies. Exposure to granisetron occurred in the first trimester in 88 patients (94 fetuses). Maternal characteristics, history of anomalies in first degree relatives, co-exposure to other substances and extent of prenatal sonographic surveillance were comparable between both groups. Miscarriage rate was significantly lower among granisetron exposed patients compared to controls (0 vs 5.5 %, respectively, p = 0.03). Three major malformations were identified prenatally or postnatally in each of the groups (2.77 % Vs 2.83 %, p = 1). The rate of major malformations was similar between exposed and unexposed fetuses even after excluding second trimester exposure (3.2 % vs. 2.83 %, respectively p = 1). Mean gestational age at delivery, mean newborn weight and incidence of small for gestation age, were not significantly different between the groups.

CONCLUSION

Granisetron exposure was not associated with increased risk for minor or major fetal anomalies. This study provides preliminary reassurance regarding the safety of in-utero exposure to granisetron.

A Physiologically Based Pharmacokinetic Model for Pregnant Women to Predict the Pharmacokinetics of Drugs Metabolized Via Several Enzymatic Pathways

BACKGROUND

Physiologically based pharmacokinetic modeling is considered a valuable tool for predicting pharmacokinetic changes in pregnancy to subsequently guide in-vivo pharmacokinetic trials in pregnant women. The objective of this study was to extend and verify a previously developed physiologically based pharmacokinetic model for pregnant women for the prediction of pharmacokinetics of drugs metabolized via several cytochrome P450 enzymes.

METHODS

Quantitative information on gestation-specific changes in enzyme activity available in the literature was incorporated in a pregnancy physiologically based pharmacokinetic model and the pharmacokinetics of eight drugs metabolized via one or multiple cytochrome P450 enzymes was predicted. The tested drugs were caffeine, midazolam, nifedipine, metoprolol, ondansetron, granisetron, diazepam, and metronidazole. Pharmacokinetic predictions were evaluated by comparison with in-vivo pharmacokinetic data obtained from the literature.

RESULTS

The pregnancy physiologically based pharmacokinetic model successfully predicted the pharmacokinetics of all tested drugs. The observed pregnancy-induced pharmacokinetic changes were qualitatively and quantitatively reasonably well predicted for all drugs. Ninety-seven percent of the mean plasma concentrations predicted in pregnant women fell within a twofold error range and 63% within a 1.25-fold error range. For all drugs, the predicted area under the concentration-time curve was within a 1.25-fold error range.

CONCLUSION

The presented pregnancy physiologically based pharmacokinetic model can quantitatively predict the pharmacokinetics of drugs that are metabolized via one or multiple cytochrome P450 enzymes by integrating prior knowledge of the pregnancy-related effect on these enzymes. This pregnancy physiologically based pharmacokinetic model may thus be used to identify potential exposure changes in pregnant women a priori and to eventually support informed decision making when clinical trials are designed in this special population.

Implications of genetic variation of common Drug Metabolizing Enzymes and ABC Transporters among the Pakistani Population

Genetic polymorphism of drug metabolizing enzymes and transporters may influence drug response. The frequency varies substantially between ethnicities thus having implications on appropriate selection and dosage of various drugs in different populations. The distribution of genetic polymorphisms in healthy Pakistanis has so far not been described. In this study, 155 healthy adults (98 females) were included from all districts of Karachi. DNA was extracted from saliva and genotyped for relevant SNVs in CYP1A1, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4 and CYP3A5 as well as ALDH3A1, GSTA1, ABCB1 and ABCC2. About 64% of the participants were born to parents who were unrelated to each other. There was generally a higher prevalence (p < 0.05) of variant alleles of CYP450 1A2, 2B6, 2C19, 3A5, ALDH3A1, GSTM1 as well as ABCB1 and ABCC2 in this study cohort than in other ethnicities reported in the HapMap database. In contrast, the prevalence of variant alleles was lower in GSTA1. Therefore, in the Pakistani population sample from Karachi a significantly different prevalence of variant drug metabolizing enzymes and ABC transporters was observed as compared to other ethnicities, which could have putative clinical consequences on drug efficacy and safety.