Sex differences in the pharmacokinetics and bioequivalence of the delayed-release combination of doxylamine succinate-pyridoxine hydrochloride; implications for pharmacotherapy in pregnancy

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

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

Evaluation of sex-by-formulation interaction in bioequivalence studies of efavirenz tablets

AIMS

The existence of a sex-by-formulation interaction in bioequivalence studies implies that the bioequivalence results (i.e., the test/reference ratio of the pharmacokinetic parameters) obtained in one sex are not similar to those obtained in the other sex. Therefore, results obtained in studies including only males would not be representative of the results that would have been obtained in females and vice versa. Recently, a sex-by-formulation interaction has been reported in a study for efavirenz tablets. The purpose of this paper is to investigate whether a sex-by-formulation interaction is actually observed in the bioequivalence studies conducted with efavirenz tablets.

METHODS

The existence of sex-by-formulation interaction was investigated in the two studies conducted in our centre, where the same test and reference products were investigated in a pilot study with 12 subjects and a pivotal study with 36 subjects.

RESULTS

In the pilot study, the point estimates for the test/reference ratio of geometrics means of C_max in females and males were more than 20% different (95.42% vs.79.38%, i.e., 120.21%), but in a subsequent pivotal study the difference was less than 2% (111.14% vs. 109.98%, i.e., 101.66%).

CONCLUSIONS

A sex-by-formulation interaction is suggested in the study with a small sample size, but it disappears when the study is repeated with a larger sample size. In conclusion, the analysis of subgroups should be conducted with caution when the size of the subgroups is not powered to show bioequivalence. There seems to be no reason to require bioequivalence studies for efavirenz in both sexes.

Age and sex in drug development and testing for adults

Individualization of drug therapy requires that the right drug be administered at the correct dose to patients who are likely to achieve the highest benefit and lowest risk. Female sex and age comprise two important risk factors for altered drug exposure and response. This review summarizes the current state of science for considering age and sex-related factors along the drug development pipeline, from cell culture and animal research through all phases of clinical trials in humans. A set of recommendations is provided to improve standards for integrating age and sex into the study design, analysis, and reporting of pre-clinical and clinical assessment of new molecular entities and biologics in adults.

The delayed-release combination of doxylamine and pyridoxine (Diclegis®/Diclectin ®) for the treatment of nausea and vomiting of pregnancy

Nausea and vomiting of pregnancy (NVP) affects up to 85 % of all pregnancies. Effective treatment can greatly improve a woman's quality of life, reduce the risk for maternal and fetal complications, and reduce healthcare costs. Unfortunately, many women receive either no pharmacological treatment or are recommended therapies for which fetal safety and efficacy have not been established. First-line treatment of NVP, as recommended by several leading healthcare and professional organizations, is the combination of doxylamine and pyridoxine. This combination, formulated as a 10 mg/10 mg delayed-release tablet, was approved by the US Food and Drug Administration (FDA) for the treatment of NVP in April 2013 under the brand name Diclegis(®), and has been on the Canadian market since 1979, currently under the brand name Diclectin(®). The efficacy of Diclegis(®)/Diclectin(®) has been demonstrated in several clinical trials, and, more importantly, studies on more than 200,000 women exposed to doxylamine and pyridoxine in the first trimester of pregnancy have demonstrated no increased fetal risk for congenital malformations and other adverse pregnancy outcomes. The present review aims to present the scientific evidence on the effectiveness and fetal safety of Diclegis(®)/Diclectin(®) for the treatment of NVP to justify its use as first-line treatment for NVP.