Pharmacokinetic interactions between contraceptives and antiepileptic drugs

The impact of pregnancy-related hormonal and physiological changes on antiseizure medications: expert perspective

INTRODUCTION

Epilepsy is a disorder of recurrent, unprovoked seizures affecting approximately 15 million individuals of childbearing potential worldwide. Patients with epilepsy rely on regular daily therapy with antiseizure medications (ASMs). Furthermore, ASMs are also prescribed for other neuropsychiatric indications (e.g. bipolar disorder, pain, migraines) with over 2% of the pregnancies in the United States involving prenatal exposure to ASMs.

AREAS COVERED

ASM concentrations are affected by hormonal and physiological changes in pregnancy, including increases in renal and hepatic blood flow, decreased protein binding, and changes in enzyme activity. Clearance changes typically reverse within a few weeks after delivery. During pregnancy, many ASMs, such as lamotrigine, levetiracetam, and oxcarbazepine, should have serum concentrations monitored and doses increased to maintain the individualized target range for seizure control. ASMs metabolized via glucuronidation, primarily lamotrigine, undergo marked increases in clearance throughout pregnancy, requiring about 3-fold the pre-pregnancy daily dose by delivery. Postpartum, ASM doses are usually decreased over several weeks to prevent drug toxicity.

EXPERT OPINION

In the future, the development of a physiologically-based pharmacokinetic model for various ASMs may enable empiric dose adjustments in pregnancy without the difficulties of frequent therapeutic drug monitoring.

Effect of P. corylifolia on the pharmacokinetic profile of tofacitinib and the underlying mechanism

This work aimed to explore the mechanisms underlying the interaction of the active furanocoumarins in P. corylifolia on tofacitinib both in vivo and in vitro. The concentration of tofacitinib and its metabolite M8 was determined using UPLC-MS/MS. The peak area ratio of M8 to tofacitinib was calculated to compare the inhibitory ability of furanocoumarin contained in the traditional Chinese medicine P. corylifolia in rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant human CYP3A4 (rCYP3A4). We found that bergapten and isopsoralen exhibited more significant inhibitory activity in RLMs than other furanocoumarins. Bergapten and isopsoralen were selected to investigate tofacitinib drug interactions in vitro and in vivo. Thirty rats were randomly allocated into 5 groups (n = 6): control (0.5% CMC-Na), low-dose bergapten (20 mg/kg), high-dose bergapten (50 mg/kg), low-dose isopsoralen (20 mg/kg) and ketoconazole. 10 mg/kg of tofacitinib was orally intervented to each rat and the concentration level of tofacitinib in the rats were determined by UPLC-MS/MS. More imporrantly, the results showed that bergapten and isopsoralen significantly inhibited the metabolism of tofacitinib metabolism. The AUC(0-t), AUC(0-∞), MRT(0-t), MRT(0-∞) and Cmax of tofacitinib increased in varying degrees compared with the control group (all p < 0.05), but CLz/F decreased in varying degrees (p < 0.05) in the different dose bergapten group and isopsoralen group. Bergapten, isopsoralen and tofacitinib exhibit similar binding capacities with CYP3A4 by AutoDock 4.2 software, confirming that they compete for tofacitinib metabolism. P. corylifolia may considerably impact the metabolism of tofacitinib, which can provide essential information for the accurate therapeutic application of tofacitinib.

Factors influencing community pharmacists' knowledge about women's issues in epilepsy

Background

Previous studies have highlighted instances where pharmacists lacked knowledge regarding women's health issues related to epilepsy.

Objectives

To assess UAE community pharmacists' knowledge, toward women's issues in epilepsy.

Methods

a cross-sectional research method was employed. A team of seven pharmacy students in their final year visited a randomly selected sample of community pharmacies in the UAE and face-to-face interviews were conducted with the pharmacists using a structured questionnaire. The questionnaire includes two parts; Eight questions designed to elicit data about the demographics of the study participants and 12 questions eliciting insights into the participants' knowledge of women's issues in epilepsy.

Results

A total of 412 community pharmacist were recruited in the study. The overall level of knowledge about women's issues in epilepsy was good and the average knowledge score was 81% with a 95% confidence interval (CI) [79.1, 82.7%]. The results of multivariate analysis showed higher knowledge scores in chain pharmacies (OR 1.37; 95% CI 1.12-1.67), Chief pharmacists (OR 1.44; 95% CI 1.01-2.06), Pharmacists in charge (OR 3.46; 95% CI 2.7-4.45), pharmacists with 1-5 Years of experience (OR 2.87; 95% CI 1.71-4.82), pharmacists with 6-10 Years (OR 2.63; 95% CI 1.58-4.38), pharmacists with >10 years (OR 3.13; 95% CI 2.03-4.83), graduation form regional universities (OR 1.37; 95% CI 1.12-1.67), graduation form international universities (OR 1.73; 95% CI 1.36-2.20) and receiving a training on epilepsy (OR 1.36; 95% CI 1.12-1.67).

Conclusion

While the findings reveal an overall promising level of knowledge among community pharmacists regarding the issues faced by women with epilepsy, pinpointing which clinical and demographic factors have the most significant impact on this knowledge would permit the implementation of tailored educational interventions. Workshops and modules targeting the issues faced by women with epilepsy would further raise the knowledge and competence among community pharmacists in this area, ensuring better pharmaceutical care for this population.

Important Drug-Drug Interactions for the Addiction Psychiatrist

The misuse of illicit substances, prescribed medications, and alcohol poses obvious health risks to afflicted individuals. When addressing these health risks, the overarching concerns generally relate to the direct effects that various substances can have on the functioning of multiple organ systems: cardiac, pulmonary, central nervous system, and others. What is not always evident, but potentially equally or even more dire, are the risks arising from drug-drug interactions involving illicit drugs and alcohol, whether with each other, or with prescribed medications. This review provides some basics that enable the reader to fruitfully approach the broad topic of drug-drug interactions.

Differential risks of changes in seizure frequency with transitions between hormonal and non-hormonal contraception in women with epilepsy: A prospective cohort study

This prospective, observational, cohort study of 101 women with epilepsy (WWE) assesses the seizure safety of systemic hormonal contraception (HC) versus non-HC (NHC). It reports risks of changes in seizure frequency associated with transition from NHC to HC relative to HC to NHC for (1) proportions of WWE with ≥50% increase and decrease in seizure frequency, (2) changes in seizure frequency, (3) changes in seizure severity, and 4) changes in AED regimen during the study. In comparing NHC to HC versus HC to NHC, NHC to HC had greater risk of ≥50% increase in seizure frequency: RR = 1.98 (1.07-3.64), p = 0.03 and lower risk of ≥50% decrease in seizure frequency: RR = 0.42 (0.22 = 0.83), p = 0.01. These risks were particularly notable for oral contraceptive pill: RR = 2.91 (1.26-6.72), p = 0.01 and RR = 0.54 (0.30-0.97), p = 0.04, respectively. Median monthly seizure frequency (MMSF) increased 302.0% (p = 0.0019) with transition from NHC to HC. MMSF decreased 81.9% with change from HC to NHC (p = 0.001). RR for change in seizure type from milder to more severe type was greater for NHC to HC: RR = 3.32 (1.07-10.27), p = 0.04. Change in AED regimen was not a significant factor. The findings suggest further prospective study to assess whether HC, especially oral contraceptive pill, poses a greater risk of increased seizures than NHC.

Evaluation of the Potential Pharmacokinetic Interactions Between Vixotrigine and an Oral Contraceptive

BACKGROUND AND OBJECTIVE

Vixotrigine is a voltage- and use-dependent sodium channel blocker in development for neuropathic pain management. This study evaluated the effect of coadministration of vixotrigine (metabolized primarily via uridine diphosphate-glucuronosyltransferases) and an oral contraceptive containing ethinyl estradiol (uridine diphosphate-glucuronosyltransferase inducer) and levonorgestrel on the pharmacokinetics and safety of all three compounds.

METHODS

In this phase I, open-label, fixed-sequence, multiple-dose study, 36 healthy women received oral vixotrigine 150 mg three times daily for 6 days and once on day 7. This was followed by a washout period, days 8-11. The oral contraceptive was administered alone on days 12-25 and with vixotrigine 150 mg three times daily on days 26-32. Serial blood samples were collected for pharmacokinetic analysis. Safety was assessed.

RESULTS

The geometric least-squares mean ratios (90% confidence intervals) for the area under the concentration-time curve over 8 h and maximum concentration of vixotrigine co-administered with an oral contraceptive vs vixotrigine alone were 0.85 (0.82-0.89) and 0.91 (0.87-0.96), respectively. The geometric least-squares mean ratios (90% confidence interval) for area under the concentration-time curve over 24 h and maximum concentration of ethinyl estradiol with vixotrigine vs ethinyl estradiol alone were 0.94 (0.91-0.97) and 0.89 (0.84-0.94), respectively; the ratios for levonorgestrel with vixotrigine vs levonorgestrel alone were 1.06 (0.98-1.16) and 1.05 (0.98-1.13), respectively. No adverse events occurring with vixotrigine alone were deemed related to the study drug by the investigators.

CONCLUSIONS

Coadministration of vixotrigine and an oral contraceptive containing ethinyl estradiol and levonorgestrel had no clinically relevant effect on exposure of all three compounds.

TRIAL REGISTRATION

ClinicalTrials.gov registration number: NCT03324685 (registered 25 October, 2017).

Xenobiotica-metabolizing enzyme induction potential of chemicals in animal studies: NanoString nCounter gene expression and peptide group-specific immunoaffinity as accelerated and economical substitutions for enzyme activity determinations?

Xenobiotica-metabolizing enzyme (XME) induction is a relevant biological/biochemical process vital to understanding the toxicological profile of xenobiotics. Early recognition of XME induction potential of compounds under development is therefore important, yet its determination by traditional XME activity measurements is time consuming and cost intensive. A proof-of-principle study was therefore designed due to the advent of faster and less cost-intensive methods for determination of enzyme protein and transcript levels to determine whether two such methods may substitute for traditional measurement of XME activity determinations. The results of the study show that determination of enzyme protein levels by peptide group-specific immunoaffinity enrichment/MS and/or determination of gene expression by NanoString nCounter may serve as substitutes for traditional evaluation methodology and/or as an early predictor of potential changes in liver enzymes. In this study, changes of XME activity by the known standard XME inducers phenobarbital, beta-naphthoflavone and Aroclor 1254 were demonstrated by these two methods. To investigate the applicability of these methods to demonstrate XME-inducing activity of an unknown, TS was also examined and found to be an XME inducer. More specifically, TS was found to be a phenobarbital-type inducer (likely mediated by CAR rather than PXR as nuclear receptor), but not due to Ah receptor-mediated or antioxidant response element-mediated beta-naphthoflavone-type induction. The results for TS were confirmed via enzymatic activity measurements. The results of the present study demonstrate the potential applicability of NanoString nCounter mRNA quantitation and peptide group-specific immunoaffinity enrichment/MS protein quantitation for predicting compounds under development to be inducers of liver XME activity.

Bidirectional interaction between oral contraception and lamotrigine in women with epilepsy - Role of progestins

PURPOSE

To investigate the effects of various progestins in combined oral contraceptives (COCs) on lamotrigine (LTG) serum concentrations and, vice versa, the potential impact of LTG on progestin serum levels during the menstrual cycle.

METHODS

Twenty women with epilepsy (WWE) undergoing LTG monotherapy and COC (LTG group; mean ± SD [median; range] age 24.2 ± 4.6 [23.0; 18-37] years) as well as fourteen controls on COC (24.9 ± 5.6 [22.5; 20-39] years) were assessed for eligibility and all agreed to participate in the study and remained for data analyses.

RESULTS

LTG levels differed significantly between phases of inactive pill and active pill use (p= 0.004), particularly with drospirenon (p= 0.018) and levonorgestrel (p= 0.068) as progestogen component but not with gestoden (p= 0.593). Furthermore, the LTG group showed significantly lower progestin levels during inactive pill when compared to active pill use with respect to levonorgestrel (p= 0.042) and drospirenon (p= 0.018) but not to gestoden (p= 0.109). Progestin concentrations did not differ between patients and controls (p> 0.05).

CONCLUSIONS

The findings suggest that drospirenon and levonorgestrel but not gestoden seem to reduce LTG serum concentrations when being co-administered in WWE which might be of importance concerning seizure risk. Vice versa, no effect of LTG on several progestins could be demonstrated, arguing against a potential loss of contraception safety with LTG.

Prevalence of highly effective contraception use by women with epilepsy

OBJECTIVE

To determine (1) the proportion of women with epilepsy (WWE) at risk of unintended pregnancy who use highly effective contraception, (2) demographic predictors, and (3) folic acid (FA) use.

METHODS

These cross-sectional data come from 311 US WWE, 18-47 years, who participated in the Epilepsy Birth Control Registry (EBCR) web-based survey in 2017. They provided demographic, epilepsy, antiepileptic drug (AED), contraceptive, and FA data. We report frequencies of highly effective contraception use and use logistic regression to determine demographic predictors. We report the proportion who take FA.

RESULTS

A total of 186 (59.8%) of the 311 WWE were at risk of unintended pregnancy. A total of 131 (70.4%) used a highly effective contraceptive category; 55 (29.6%) did not. An additional 13 (7.0%) used a combination of generally effective hormonal contraception with an enzyme-inducing AED, which poses increased risk of unintended pregnancy. Overall, 68 (36.6%) of the 186 WWE at risk did not use highly effective contraception. Increasing income (p = 0.004) and having insurance (p = 0.048) were predictors of highly effective contraception. A total of 50.0% took FA supplement. There was no significant difference in relation to the use or lack of use of highly effective contraception.

CONCLUSION

A total of 36.6% of WWE in the EBCR did not use highly effective contraception and 50.0% did not take FA in 2017 despite the important negative consequences of unintended pregnancy on pregnancy outcomes. There is a need for more readily available information and counseling on safe and effective contraception and FA use for this community.

Silymarin as a flavonoid-type P-glycoprotein inhibitor with impact on the pharmacokinetics of carbamazepine, oxcarbazepine and phenytoin in rats

P-glycoprotein (P-gp) is an efflux transporter involved in drug-resistant epilepsy and some flavonoids have been targeted as effective P-gp inhibitors. Herein, we assessed the impact of silymarin on the pharmacokinetics of three antiepileptic drugs (AEDs) in rats. Animals were pretreated with silymarin, verapamil (positive control) or vehicle (negative control) 1 h before AEDs administration (carbamazepine (25 mg/kg), oxcarbazepine (OXC) (50 mg/kg), or phenytoin (100 mg/kg)). Multiple blood samples were collected after AED dosing, and a non-compartmental analysis was performed. An independent study was also conducted to investigate the effects of silymarin on the OXC plasma-to-brain distribution. Silymarin altered the pharmacokinetics of OXC, increasing its peak plasma concentration by 50% and its extent of systemic exposure by 41%, which had also impact on brain drug concentrations. These findings support that the co-administration of silymarin and OXC should continue to be explored as a strategy to reverse the pharmacoresistance in epilepsy.

Tezacaftor for the treatment of cystic fibrosis

INTRODUCTION

Cystic fibrosis (CF) is the most common, life-limiting autosomal recessive disease in Caucasians, and is caused by defects in production of the CFTR ion channel. Until recently, there were no available treatments targeting the disease-causing defects in CFTR but newly developed CFTR modulators are changing the course of disease in CF. The newest modulator, tezacaftor, is a CFTR corrector that was recently approved by the FDA to be used in combination with the first approved CFTR potentiator, ivacaftor. Areas covered: A detailed review of the clinical trials and published literature, focusing on safety and efficacy, leading to the approval of tezacaftor in CF. Expert commentary: Recent trials have demonstrated that the combination of tezacaftor-ivacaftor is a slightly superior combination to its predecessor, lumacaftor-ivacaftor, with respect to an increase in FEV1, adverse event profile, and drug-drug interactions. It is also approved for a large number of non-F508del, residual function mutations that are predicted to respond based on in vitro testing. The horizon for continued improvements in CFTR-targeted treatments is promising, with three-drug combinations currently in Phase 3 clinical trials, and other drugs with novel mechanisms of action being studied. Within the next 5 years, the vast majority of patients with CF are expected to have a modulator approved for their genotype.

Linking physiologically-based pharmacokinetic and genome-scale metabolic networks to understand estradiol biology

Background

Estrogen is a vital hormone that regulates many biological functions within the body. These include roles in the development of the secondary sexual organs in both sexes, plus uterine angiogenesis and proliferation during the menstrual cycle and pregnancy in women. The varied biological roles of estrogens in human health also make them a therapeutic target for contraception, mitigation of the adverse effects of the menopause, and treatment of estrogen-responsive tumours. In addition, endogenous (e.g. genetic variation) and external (e.g. exposure to estrogen-like chemicals) factors are known to impact estrogen biology. To understand how these multiple factors interact to determine an individual’s response to therapy is complex, and may be best approached through a systems approach.

Methods

We present a physiologically-based pharmacokinetic model (PBPK) of estradiol, and validate it against plasma kinetics in humans following intravenous and oral exposure. We extend this model by replacing the intrinsic clearance term with: a detailed kinetic model of estrogen metabolism in the liver; or, a genome-scale model of liver metabolism. Both models were validated by their ability to reproduce clinical data on estradiol exposure. We hypothesise that the enhanced mechanistic information contained within these models will lead to more robust predictions of the biological phenotype that emerges from the complex interactions between estrogens and the body.

Results

To demonstrate the utility of these models we examine the known drug-drug interactions between phenytoin and oral estradiol. We are able to reproduce the approximate 50% reduction in area under the concentration-time curve for estradiol associated with this interaction. Importantly, the inclusion of a genome-scale metabolic model allows the prediction of this interaction without directly specifying it within the model. In addition, we predict that PXR activation by drugs results in an enhanced ability of the liver to excrete glucose. This has important implications for the relationship between drug treatment and metabolic syndrome.

Conclusions

We demonstrate how the novel coupling of PBPK models with genome-scale metabolic networks has the potential to aid prediction of drug action, including both drug-drug interactions and changes to the metabolic landscape that may predispose an individual to disease development.

Electronic supplementary material

The online version of this article (10.1186/s12918-017-0520-3) contains supplementary material, which is available to authorized users.

Reasons for discontinuation of reversible contraceptive methods by women with epilepsy

OBJECTIVE

To report the reasons for discontinuation of contraceptive methods by women with epilepsy (WWE).

METHODS

These retrospective data come from a web-based survey regarding the contraceptive practices of 1,144 WWE in the community, ages 18-47 years. We determined the frequencies of contraceptive discontinuations and the reasons for discontinuation. We compared risk ratios for rates of discontinuation among contraceptive methods and categories. We used chi-square analysis to test the independence of discontinuation reasons among the various contraceptive methods and categories and when stratified by antiepileptic drug (AED) categories.

RESULTS

Nine hundred fifty-nine of 2,393 (40.6%) individual, reversible contraceptive methods were discontinued. One-half (51.8%) of the WWE who discontinued a method discontinued at least two methods. Hormonal contraception was discontinued most often (553/1,091, 50.7%) with a risk ratio of 1.94 (1.54-2.45, p < 0.0001) compared to intrauterine devices (IUDs), the category that was discontinued the least (57/227, 25.1%). Among all individual methods, the contraceptive patch was stopped most often (79.7%) and the progestin-IUD was stopped the least (20.1%). The top three reasons for discontinuation among all methods were reliability concerns (13.9%), menstrual problems (13.5%), and increased seizures (8.6%). There were significant differences among discontinuation rates and reasons when stratified by AED category for hormonal contraception but not for any other contraceptive category.

SIGNIFICANCE

Contraception counseling for WWE should consider the special experience profiles that are unique to this special population on systemic hormonal contraception.

Adverse Effects in the Pharmacologic Management of Bipolar Disorder During Pregnancy

Management of bipolar disorder during pregnancy often involves medications with potential adverse effects, including risks to the mother and fetus. Although some specifics are known, many medications continue to have incompletely characterized reproductive safety profiles. Women with bipolar disorder who are planning pregnancy face challenging decisions about their treatment; careful risk-benefit discussions are necessary. With the goal of further informing these discussions, this article reviews the data currently available regarding medication safety in the management of bipolar disorder during pregnancy, with specific attention to lithium, valproic acid, lamotrigine, carbamazepine, and antipsychotic medications.

Differential impact of contraceptive methods on seizures varies by antiepileptic drug category: Findings of the Epilepsy Birth Control Registry

PURPOSE

The aim of this study was to determine whether categories of contraception differ in their impact on seizures in women with epilepsy and whether the impact varies by antiepileptic drug category.

METHODS

Retrospective survey data came from 2712 contraceptive experiences reported by 1144 women with epilepsy. We compared risk ratios for reports of increase and decrease in seizure frequency on hormonal versus nonhormonal contraception, stratified by antiepileptic drug categories.

RESULTS

More women with epilepsy reported a change in seizures on hormonal (28.2%) than on nonhormonal contraception (9.7%) (p<0.0001). The risk ratio for seizure increase on hormonal (18.7%) versus nonhormonal contraception (4.2%) was 4.47 (p<0.0001). The risk ratio for seizure decrease on hormonal (9.5%) versus nonhormonal contraception (5.5%) was 1.71, p<0.0001. On hormonal contraception, the risk ratio for seizure increase was greater than for decrease (1.98, p<0.0001). In comparison to combined pills, both hormonal patch and progestin-only pills had greater risk ratios for seizure increase. Depomedroxyprogesterone was the only hormonal method with a greater risk ratio for seizure decrease than combined pills. Seizure increase was greater for hormonal than nonhormonal contraception for each antiepileptic drug category (p<0.001). On hormonal contraception, relative to the non-enzyme-inducing antiepileptic drug category which had the lowest rate, each of the other categories had significantly greater risks for seizure increase, especially the enzyme-inhibiting (valproate) category (risk ratio=2.53, p=0.0002).

CONCLUSION

The findings provide community-based, epidemiological survey evidence that contraceptive methods may differ in their impact on seizures and that this impact may vary by antiepileptic drug category.

Protective effects of Artemisia arborescens essential oil on oestroprogestative treatment induced hepatotoxicity

BACKGROUND

Currently, natural products have been shown to exhibit interesting biological and pharmacological activities and are used as chemotherapeutic agents. The purpose of this study, conducted on Wistar rats, was to evaluate the beneficial effects of Artemisia arborescens oil on oestroprogestative treatment induced damage on liver.

MATERIALS/METHODS

A total of 36 Wistar rats were divided into 4 groups; a control group (n = 9), a group of rats who received oestroprogestative treatment by intraperitoneal injection (n = 9), a group pre-treated with Artemisia arborescens then injected with oestroprogestative treatment (n = 9), and a group pre-treated with Artemisia arborescens (n = 9). To minimize the handling stress, animals from each group were sacrificed rapidly by decapitation. Blood serum was obtained by centrifugation and the livers were removed, cleaned of fat, and stored at -80℃ until use.

RESULTS

In the current study, oestroprogestative poisoning resulted in oxidative stress, which was demonstrated by 1) a significant increase of lipid peroxidation level in hepatic tissue 2) increased levels of serum transaminases (aspartate amino transferase and serum alanine amino transferase), alkaline phosphatase, glycemia and triglycerides and a decrease in the level of cholesterol 3) alteration of hepatic architecture. Pre-administration of Artemisia arborescens oil was found to alleviate oestroprogestative treatment induced damage by lowering lipid peroxidation level and by increasing activity of catalase, superoxide-dismutase, and glutathione-peroxidase in liver and by reducing disruption of biochemical parameters.

CONCLUSION

Therefore, the results obtained in this study confirmed that Artemisia essential oil protects against oestroprogestative administration induced hepatotoxicity by restoration of liver activities.

Perampanel efficacy and safety by gender: Subanalysis of phase III randomized clinical studies in subjects with partial seizures

The antiepileptic drug (AED) perampanel is approved in ≥40 countries as adjunctive therapy for drug‐resistant partial seizures in patients with epilepsy. This post hoc analysis of pooled data from three phase III, double‐blind, randomized studies of perampanel examines between‐gender differences in perampanel efficacy and safety. Of the 1,478 subjects in the pooled analysis (719 male, 759 female), 1,109 were included in the pharmacokinetic/pharmacodynamic analysis. Perampanel oral clearance was 17% lower in female than in male patients not receiving enzyme‐inducing AEDs. Pooled efficacy analysis revealed that seizure frequency was reduced with perampanel treatment regardless of gender; a greater numerical reduction in seizure frequency and increased responder rates occurred in female participants at perampanel doses of 4, 8, and 12 mg. Tolerability was similar between groups, although common adverse events such as dizziness and headache occurred more frequently in female subjects. Modest elevations in perampanel exposure in female patients may result in meaningful between‐gender differences in efficacy and safety; therefore, dosing should be individualized and clinical response monitored.

Lurasidone drug-drug interaction studies: a comprehensive review

BACKGROUND

To evaluate potential drug-drug interactions with the atypical antipsychotic lurasidone.

METHODS

Seven phase I studies were conducted to investigate the effects of repeated dosing of ketoconazole, diltiazem, rifampin, or lithium on the pharmacokinetics (PK) of single oral doses of lurasidone, or the effects of repeated dosing of lurasidone on the PK of digoxin, midazolam, or the oral contraceptive norgestimate/ethinyl estradiol. Two 6-week, phase III studies included evaluation of the potential for interaction between lurasidone and lithium or valproate. Maximum serum or plasma concentration (Cmax) and area under the concentration-time curve (AUC) were calculated.

RESULTS

Concomitant ketoconazole administration resulted in a 6.8-fold increase in lurasidone Cmax and a 9.3-fold increase in lurasidone AUC; concomitant diltiazem administration resulted in 2.1- and 2.2-fold increases, respectively. Rifampin decreased lurasidone Cmax and AUC (one-seventh and one-fifth of lurasidone alone, respectively). Steady-state dosing with lurasidone increased Cmax and AUC0-24 (AUC from time 0 to 24 h postdose) of digoxin by 9% and 13%, respectively, and of midazolam by 21% and 44%, respectively. There were no significant interactions between lurasidone and lithium, valproate, ethinyl estradiol, or norelgestromin (the major active metabolite of norgestimate).

CONCLUSIONS

Lurasidone PK is altered by strong cytochrome P450 (CYP) 3A4 inhibitors or inducers, and coadministration is contraindicated; whereas moderate CYP3A4 inhibitors have less effect, and lurasidone dosage restrictions are recommended. No dose adjustment for lurasidone is needed when administered with lithium or valproate. Dose adjustment is not required for lithium, valproate, digoxin (a P-glycoprotein substrate), or midazolam or oral contraceptives (CYP3A4 substrates) when coadministered with lurasidone.

Differential impact of antiepileptic drugs on the effects of contraceptive methods on seizures: Interim findings of the epilepsy birth control registry

PURPOSE

To present the interim findings of the Epilepsy Birth Control Registry (EBCR) regarding the impact of various contraceptive methods on seizures, stratified by antiepileptic drug (AED) type.

METHODS

This is an observational study that reports interim findings on the first 750 subjects.

RESULTS

There are significantly greater relative risks (RR) for both seizure increase and decrease with hormonal contraception (HC) than with non-hormonal contraception (NHC). The rates of HC experiences associated with seizure increase (21.0%) are greater than with NHC (3.9%) (RR=5.39 [95% CI=3.77-7.73, p<0.0001]). The rates of HC experiences associated with seizure decrease (10.3%) are greater than with NHC (5.6%) (RR=1.85 [95% CI=1.30-2.62, p=0.0006]). While differences can reflect biological effects or reporting bias, the finding of a greater RR for seizure increase with hormonal patch than with combined oral contraceptive, perhaps related to the delivery of substantially higher concentrations of hormones, and a greater RR for seizure decrease with depomedroxyprogesterone, known to reduce seizure frequency when used in dosages which produce amenorrhea, support biological effects. All AED categories showed significantly higher frequencies of reports of seizure increase when combined with HC than with NHC. RR for seizure increase with HC was higher with valproate than with any other AED category. There were no significant differences among AEDs for seizure decrease with HC at this juncture of the study. Overall, NEIAEDs had the most favorable profile with regard to reports of seizure increase and decrease when used with HC.

CONCLUSIONS

Interim EBCR findings suggest that contraception category and interactions between contraception category and AED category are predictive factors for changes in seizure frequency in WWE.

Estradiol and weight are covariates of paracetamol clearance in young women

AIM

Paracetamol clearance differs between pregnant and non-pregnant women and between women with or without specific oral contraceptives (OCs). However, an association between female sex hormones and paracetamol clearance has never been explored.

METHODS

In total, 49 women at delivery, 8 female control subjects without OC use, historical data of 14 women taking OCs, and 15 postpartum observations with and without OCs were pooled to explore covariates of paracetamol clearance. All received a single intravenous 2-gram paracetamol dose, and blood samples were collected up to 6 h after dosing. High-performance liquid chromatography was used to quantify paracetamol. The area under the curve to time infinity (AUC0-∞) was determined and clearance (l/h·m(2)) was calculated by dose/ AUC0-∞. In addition, estradiol and progesterone were quantified by ELISA with electro-chemiluminescence.

RESULTS

Median paracetamol clearance at delivery was significantly higher when compared to postpartum or non-pregnant women (11.9 vs. 6.42 and 8.4 l/h·m(2), at least p < 0.05), while an association between paracetamol clearance and estradiol was observed (R = 0.494, p < 0.0001). In non-pregnant subjects, there was no impact of OC exposure on paracetamol clearance. Multiple regression revealed a linear association (Radj = 0.41, p < 0.001) between paracetamol clearance and weight (p = 0.0462) and estradiol (p < 0.0001).

CONCLUSION

Estradiol and weight in part explain the variation in paracetamol clearance in young women.

Interaction between brivaracetam (100 mg/day) and a combination oral contraceptive: a randomized, double-blind, placebo-controlled study

This randomized, double-blind, placebo-controlled, two-way crossover study aimed to assess the pharmacokinetic interactions between brivaracetam 100 mg/day and a combination oral contraceptive (OC) containing 30 μg ethinylestradiol and 150 μg levonorgestrel. The study was performed in 28 healthy women over five 28-day menstrual cycles: baseline (OC only), two treatment cycles with brivaracetam (50 mg b.i.d.) or placebo coadministered with OC separated by a wash-out cycle (OC only), and a follow-up cycle (OC only). The OC was administered on days 1-21 of each cycle, and brivaracetam or placebo on days 1-28 of the treatment cycles. Pharmacokinetics of ethinylestradiol and levonorgestrel were determined on day 20; brivaracetam morning trough levels on days 20 (with OC) and 29 (without OC) were compared. Cmax (maximum plasma concentration) and AUC (area under the plasma concentration versus time curve) ratios for brivaracetam versus placebo (90% confidence interval [CI]) were 0.96 (0.88-1.04) and 0.90 (0.86-0.95) for ethinylestradiol, and 0.95 (0.91-0.99) and 0.92 (0.88-0.97) for levonorgestrel, within predefined bioequivalence limits (0.80-1.25). Brivaracetam trough levels were similar on days 20 and 29 (ratio 1.08; 90% CI 0.98-1.18). No differences in breakthrough bleeding were seen across the five cycles. It was concluded that there were no interactions between brivaracetam 100 mg/day and the OC.

Clinical pharmacokinetic interactions between antiepileptic drugs and hormonal contraceptives

Contraceptive management in women with epilepsy is critical owing to the potential maternal and fetal risks if contraception or seizure management fails. This article briefly describes the pharmacokinetic interactions between antiepileptic drugs (AEDs) and hormonal contraceptives and the rational strategies that may overcome these risks. Hormonal contraception, including the use of oral contraceptives (OCs), is widely used in many women with epilepsy - there is no strong evidence of seizures worsening with their use. AEDs are the mainstay for seizure control in women with epilepsy. However, there are many factors to consider in the choice of AED therapy and hormonal contraception, since some AEDs can reduce the efficacy of OCs owing to pharmacokinetic interactions. Estrogens and progestogens are metabolized by cytochrome P450 3A4. AEDs, such as phenytoin, phenobarbital, carbamazepine, felbamate, topiramate, oxcarbazepine and primidone, induce cytochrome P450 3A4, leading to enhanced metabolism of either or both the estrogenic and progestogenic component of OCs, thereby reducing their efficacy in preventing pregnancy. OCs can also decrease the concentrations of AEDs such as lamotrigine and, thereby, increase the risk of seizures. Increased awareness of AED interactions may help optimize seizure therapy in women with epilepsy.

Distinguishing hazards and harms, adverse drug effects and adverse drug reactions : implications for drug development, clinical trials, pharmacovigilance, biomarkers, and monitoring

The terms 'adverse drug effects' and 'adverse drug reactions' are commonly used interchangeably, but they have different implications. Adverse drug reactions arise when a compound (e.g. a drug or metabolite, a contaminant or adulterant) is distributed in the same place as a body tissue (e.g. a receptor, enzyme, or ion channel), and the encounter results in an adverse effect (a physiological or pathological change), which results in a clinically appreciable adverse reaction. Both the adverse effect and the adverse reaction have manifestations by which they can be recognized: adverse effects are usually detected by laboratory tests (e.g. biochemical, haematological, immunological, radiological, pathological) or by clinical investigations (e.g. endoscopy, cardiac catheterization), and adverse reactions by their clinical manifestations (symptoms and/or signs). This distinction suggests five scenarios: (i) adverse reactions can result directly from adverse effects; (ii) adverse effects may not lead to appreciable adverse reactions; (iii) adverse reactions can occur without preceding adverse effects; (iv) adverse effects and reactions may be dissociated; and (v) adverse effects and reactions can together constitute syndromes. Defining an adverse drug reaction as "an appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product" suggests a definition of an adverse drug effect: "a potentially harmful effect resulting from an intervention related to the use of a medicinal product, which constitutes a hazard and may or may not be associated with a clinically appreciable adverse reaction and/or an abnormal laboratory test or clinical investigation, as a marker of an adverse reaction."

Pharmacodynamic and pharmacokinetic evaluation of coadministration of lacosamide and an oral contraceptive (levonorgestrel plus ethinylestradiol) in healthy female volunteers

PURPOSE

To determine whether the antiepileptic drug lacosamide affects the pharmacokinetics or pharmacodynamics of a combined oral contraceptive (OC; ethinylestradiol 0.03 mg plus levonorgestrel 0.15 mg).

METHODS

This was an open-label trial in healthy female volunteers. Eligible women entered cycle 1 of the trial on the first day of menstruation. Cycle 1 was a medication-free, run-in phase of approximately 28 days to confirm that normal ovulation occurred. Volunteers with confirmed ovulation entered the subsequent cycle and started taking OCs. After establishing ovulation suppression (defined as progesterone serum concentration <5.1 nm on day 21 of the menstrual cycle) in volunteers taking the OCs in cycle 2, lacosamide 400 mg/day was administered concomitantly in the subsequent cycle (cycle 3). The pharmacokinetic parameters of area under the concentration-time curve (AUC), maximum steady-state plasma drug concentration (Cmax ), and time to maximum concentration (tmax ) were measured for the OC components and lacosamide.

KEY FINDINGS

A total of 37 volunteers completed cycle 1, and 32 completed cycle 2. In each of the 31 volunteers who completed the trial (through cycle 3), pharmacodynamic assessment showed progesterone serum concentration was <5.1 nm on day 21 of cycle 2, when the OC was administered alone, and on day 21 of cycle 3, when lacosamide was administered concomitantly. The AUC of ethinylestradiol alone versus together with lacosamide was 1,067 ± 404 versus 1,173 ± 330 pg h/ml. Corresponding values of Cmax were 116.9 ± 48.8 versus 135.7 ± 28.6 pg/ml. For levonorgestrel, the AUC alone was 74.2 ± 21.4 versus 80.9 ± 18.5 ng h/ml with lacosamide. Corresponding values of Cmax were 6.7 ± 1.9 versus 7.4 ± 1.5 ng/ml. The AUC and Cmax point estimates and almost all 90% confidence intervals (except for Cmax of ethinylestradiol) for ethinylestradiol and levonorgestrel (with and without lacosamide) were within the conventional bioequivalence range, and no relevant changes in tmax were observed for ethinylestradiol (1.5 ± 0.6 h alone vs. 1.4 ± 0.7 h with lacosamide) or for levonorgestrel (1.5 ± 1.0 h alone vs. 1.1 ± 0.6 h with lacosamide). Lacosamide pharmacokinetics were consistent with those observed in previous studies of lacosamide alone, with values for AUC of 113.5 ± 20.7 μg h/ml, Cmax of 13.8 ± 2.2 μg/ml, and tmax of 1.1 ± 0.4 h.

SIGNIFICANCE

Lacosamide and an OC containing ethinylestradiol and levonorgestrel have low potential for drug-drug interaction; therefore, coadministration of the two drugs is unlikely to result in contraceptive failure or loss of seizure control.

Add-on lacosamide: a retrospective study on the relationship between serum concentration, dosage, and adverse events

We performed a retrospective study in patients with poorly controlled epilepsy treated with add-on lacosamide (LCM) to investigate the relationship of LCM-related adverse events with LCM serum concentration and weight-dependent dosage. We collected serum concentrations, weight-related dosages, and occurrences of the seven most frequent adverse events according to the randomized double-blind, placebo-controlled trials. Seventy of 131 patients could be sufficiently evaluated. LCM serum concentrations and weight-related dosages in patients with and without typical adverse events did not differ significantly. Closer analysis of the data suggested that dizziness as the leading adverse event occurred significantly more often if LCM was combined with classic sodium channel blockers. There was a significant correlation between LCM serum concentrations and co-medication, so there is still evidence for dependent variables that might have a relevant impact in individual cases. However, our data do not allow definition of a safety range for LCM.

Drug withdrawal after successful epilepsy surgery: how safe is it?

Discontinuation of antiepileptic drugs (AEDs) is one reason patients undergo epilepsy surgery, but little is known about the risk of seizure recurrence. We describe a prospective pilot study of withdrawal performed at our epilepsy center. Sixty completely seizure-free patients were included between 1997 and 2003. AED withdrawal was proposed 1 year after surgery after a detailed discussion of the risks and benefits. On the basis of their decision on withdrawal, patients were stratified into two cohorts (withdrawal group, N=34; control group, N=26). Discontinuation was carried out in small tapering steps over 1 year with yearly follow-up visits. Withdrawal was stopped when seizures recurred or the patients objected to further discontinuation. Twenty-six of 34 (76.5%) persons in the withdrawal group and 16 of 26 (61.5%) persons in the control group were seizure free 5 years after surgery. In this study, AED discontinuation 1 year after successful epilepsy surgery was not associated with a risk of seizure recurrence higher than that of controls.

The management of epilepsy in pregnancy

While most women with epilepsy can expect a normal pregnancy outcome, epilepsy remains a significant contributor to both maternal and perinatal morbidity. Pre-pregnancy planning must address reliable contraception and optimisation of antiepileptic drug (AED) regimens to minimise teratogenic risk while maintaining seizure control. The most recent data from the AED registries regarding malformations is presented in this review, as is the limited data on the newer AEDs and studies linking neurocognitive outcomes to AED exposure. During pregnancy, important considerations include; therapeutic drug monitoring, surveillance for obstetric complications and vigilance for seizures during the intrapartum and postpartum period.

Therapeutic product disposition in at-risk populations

In an emergency situation, such as a chemical, biological, radionuclide, nuclear or explosion (CBRNE) event, all patient populations are at increased risk of serious adverse events. Therapeutic product (TP) safety and efficacy depend on the disposition of the product through absorption, distribution, metabolism and excretion. The ability of a patient to benefit from or merely tolerate a TP can be modified by many factors, including but not limited to culture, diet, disease, environmental contaminants, genetic predisposition, stress and socioeconomic status and recent life experiences. Metabolism is considered to have the greatest effect on safety and efficacy, as chemicals not metabolised can accumulate to toxic levels. Inter-individual variances in most drug metabolism enzymes may range up to greater than 1000-fold. The fetus, neonates, infants, individuals with hormonal change, infection or prior exposure to licit or illicit products and the elderly are more susceptible to increased risk of serious adverse health effects. The critically ill are the most at risk. The at-risk populations for a serious adverse event are dependent then on the CBRNE event, their physical and cognitive states and the inter-individual intrinsic and extrinsic factors that affect TP disposition.

Female issues in epilepsy: a critical review

The focus on gender-related issues for women with epilepsy has heightened in recent years. The emphasis, however, has been on the childbearing years. Epilepsy and antiepileptic drug treatment affect sexual development, the menstrual cycle, and aspects of contraception, fertility, and reproduction. Female patients with epilepsy at a reproductive age face a unique set of reproductive issues, ranging from descriptions of disorders of reproduction in epilepsy and its causes, to contraception, pregnancy, sexuality, menopause, and osteoporosis. Conditions and diseases that specifically affect women are discussed. The role of hormones across the life cycle--endogenous and exogenous hormones and their effects on drug interactions, drug metabolism, and therapeutic outcomes--is described. Contraception and pregnancy issues for women with epilepsy have received the appropriate attention.

Topiramate-associated acute glaucoma in a migraine patient receiving concomitant citalopram therapy: a case-report

We describe the case of a 34 year-old man with diagnosis of migraine with and without aura that developed myopia and acute glaucoma after 7 days of treatment with topiramate. The patient had also been taking citalopram daily for two months. Both topiramate and citalopram have been related to the increase of intraocular pressure and the development of glaucoma. We can't exclude that in this patient citalopram caused an increase of the ocular pressure in dose-dependent manner, facilitating topiramate-induced glaucoma. We recommend to pay particular attention in prescribing of topiramate in migraine patients who are already under treatment with citalopram or other antidepressants with a similar mechanisms of action.