Interactions between antiepileptic drugs and hormonal contraception

Contraception and prenatal vitamin supplementation for women on antiepileptic medications

This article identifies interactions among AEDs with hormonal contraceptives and summarizes management strategies from the literature. Recommendations for addressing folate, vitamin K, and vitamin D deficiency caused by AEDs are also reviewed.

Reproductive and contraceptive issues in chronically ill adolescents

OBJECTIVES

To address reproductive and contraceptive issues in adolescent girls with chronic medical conditions in order to assist health-care providers when they counsel teenagers about contraceptive methods.

METHODS

The review is based on a literature search in Medline (1973-2010) about specific contraceptive use by adolescents with obesity, endocrine, cardiovascular, haematologic, oncologic, neurological, psychiatric, gastrointestinal, hepatobiliary, autoimmune, renal, pulmonary conditions and disabilities. The latest recommendations from the World Health Organisation for adolescents are also added. Contraceptive methods studied were combined hormonal contraceptives, progestogen-only contraceptives, and intrauterine contraceptives.

RESULTS

Adolescents are eligible to use any method of contraception. Contraceptive choices of chronically ill adolescents have changed over time. Given new developments in the field of adolescent sexual and reproductive health care, safe and effective forms of contraception are available for almost every adolescent with a chronic condition. When selecting a method, the nature of the medical illness and the expressed desires of the teenager must be taken into account.

CONCLUSIONS

Adolescents, including those with chronic conditions, are sexual beings; they are entitled to sexual and reproductive health care. Decisions on appropriate contraception must be based upon informed choice, after adequate sexual health education.

Continuation rates and complications of intrauterine contraception in women diagnosed with bipolar disorder

OBJECTIVE

To estimate continuation rates, complications, and psychiatric hospitalizations among women with bipolar disorder using levonorgestrel-releasing or copper-containing intrauterine devices (IUDs) as compared with those using depot medroxyprogesterone acetate or sterilization for birth control.

METHODS

Data for this cohort study were obtained from a nationwide health insurance claims database on an employed, commercially insured population. Women aged 18-44 years with a prior diagnosis of bipolar disorder (n=849) who were using the levonorgestrel intrauterine system, a copper-containing IUD, depot medroxyprogesterone acetate, or sterilization were evaluated. Outcomes included continuation rates over a 12-month interval, infectious and noninfectious complications, and hospitalizations for bipolar disorder or depression.

RESULTS

Women using an IUD were more likely than those using depot medroxyprogesterone acetate to continue the method for at least 12 months (copper-containing IUD, 86%; levonorgestrel intrauterine system, 87%). In comparison, only 31% of those who initiated depot medroxyprogesterone acetate received three more injections during the next year (P<.001). No significant differences were noted in infectious or noninfectious complications by contraceptive type. Finally, no differences were observed in the number of hospitalizations for bipolar disorder or depression among the four contraceptive groups.

CONCLUSION

More women with bipolar disorder continued using IUDs at one year than women using depot medroxyprogesterone acetate. The rates of complications and psychiatric hospitalizations were not different among women using an IUD, depot medroxyprogesterone acetate, or sterilization.

LEVEL OF EVIDENCE

II.

Adverse effects of antiepileptic drugs

More than 150 years after bromide was introduced as the first antiepileptic drug, adverse effects remain a leading cause of treatment failure and a major determinant of impaired health-related quality of life in people with epilepsy. Adverse effects can develop acutely or many years after starting treatment and can affect any organ or structure. In the past two decades, many efforts have been made to reduce the burden of antiepileptic drug toxicity. Several methods to screen and quantify adverse effects have been developed. Patient profiles associated with increased risk of specific adverse effects have been uncovered through advances in the areas of epidemiology and pharmacogenomics. Several new-generation antiepileptic drugs with improved tolerability profiles and reduced potential for drug interaction have been added to the therapeutic armamentarium. Overall, these advances have expanded the opportunities to tailor treatment with antiepileptic drugs, to enhance effectiveness and minimise the risk of toxic effects.

Concepts of contraception for adolescent and young adult women with chronic illness and disability

Sexual behavior is common in adolescents and young adults with or without chronic illness or disability, resulting in high levels of unplanned pregnancy and STDs. Individuals with chronic illness or disability should not receive suboptimal preventive health care. These individuals have a need for counseling regarding issues of sexuality and contraception. Sexually active adolescent and young adult women can be offered safe and effective contraception if they wish to avoid pregnancy. Women with chronic illnesses and disabilities who are sexually active should also be offered contraception based on their specific medical issues. Condoms are also recommended to reduce STD risks. Table 36 summarizes basic principles of contraception application for specific illnesses, which have been identified since the release of the combined OC in 1960. Clinicians should also consider the noncontraceptive benefits of this remarkable and life-changing technology that allows all reproductive age women to improve their lives, including those with chronic illnesses and disabilities.

Neuroendocrinological aspects of epilepsy: important issues and trends in future research

Neuroendocrine research in epilepsy focuses on the interface among neurology, endocrinology, gynecology/andrology and psychiatry as it pertains to epilepsy. There are clinically important reciprocal interactions between hormones and the brain such that neuroactive hormones can modulate neuronal excitability and seizure occurrence while epileptiform discharges can disrupt hormonal secretion and promote the development of reproductive disorders. An understanding of these interactions and their mechanisms is important to the comprehensive management of individuals with epilepsy. The interactions are relevant not only to the management of seizure disorder but also epilepsy comorbidities such as reproductive dysfunction, hyposexuality and emotional disorders. This review focuses on some of the established biological underpinnings of the relationship and their clinical relevance. It identifies gaps in our knowledge and areas of promising research. The research has led to ongoing clinical trials to develop hormonal therapies for the treatment of epilepsy. The review also focuses on complications of epilepsy treatment with antiepileptic drugs. Although antiepileptic drugs have been the mainstay of epilepsy treatment, they can also have some adverse effects on sexual and reproductive function as well as bone density. As longevity increases, the prevention, diagnosis and treatment of osteoporosis becomes an increasingly more important topic, especially for individuals with epilepsy. The differential effects of antiepileptic drugs on bone density and their various mechanisms of action are reviewed and some guidelines and future directions for prevention of osteoporosis and treatment are presented.

CEU; Collaborative Management of Women with Bipolar Disorder During Pregnancy and Postpartum: Pharmacologic Considerations

Bipolar disorder is a chronic condition characterized by periods of mania, depression, or mixed states (co-occurring mania and depression). The postpartum period is associated with a high risk for symptom relapse or intensification, which can be reduced with the use of medications. Abrupt discontinuation of these medications increases the probability of relapse, which is associated with high-risk behaviors, significant family dysfunction, and suicide. Drugs used to treat patients with bipolar disorder vary in teratogenic potential. Although first trimester lithium use is associated with Ebstein's anomaly, the risk was overestimated in the past. Valproate and its derivatives and carbamazepine are human teratogens. Lamotrigine does not negatively impact major reproductive outcomes, but the data are limited. Typical antipsychotic medications are relatively well studied and the data do not identify major morphologic teratogenicity. There are fewer studies of newer atypical antipsychotic medications, and registries have been developed to collect prospective data. Clinical management of bipolar disorder during pregnancy, postpartum, and lactation requires a careful balancing of maternal and fetal risks and benefits. Communication and careful comanagement between the obstetric and psychiatric team is essential when treating women with bipolar disorder during the reproductive years.

Women and epilepsy

Women with epilepsy face additional challenges when compared to their peers. Hormonal influences may increase seizure activity, alter endocrine function, and affect fertility. In this population, antiepileptic drugs (AEDs) reduce the efficacy of contraception methods and increase the risk of fetal malformations. Other pertinent issues to women with epilepsy include breastfeeding as well as bone mineral health. This article summarizes our current, collective knowledge of these issues and makes specific recommendations with respect to management.

Managing epilepsy in women of childbearing age

Epilepsy affects the menstrual cycle, aspects of contraception, fertility, pregnancy and bone health in women. It is common for seizure frequency to vary throughout the menstrual cycle. In ovulatory cycles, two peaks can be seen around the time of ovulation and in the few days before menstruation. In anovulatory cycles, there is an increase in seizures during the second half of the menstrual cycle. There is also an increase in polycystic ovaries and hyperandrogenism associated with valproate therapy. There are no contraindications to the use of non-hormonal methods of contraception in women with epilepsy. Non-enzyme-inducing antiepileptic drugs (AEDs) [valproate, benzodiazepines, ethosuximide, levetiracetam, tiagabine and zonisamide] do not show any interactions with the combined oral contraceptive (OC). There are interactions between the combined OC and hepatic microsomal-inducing AEDs (phenytoin, barbiturates, carbamazepine, topiramate [dosages>200 mg/day], oxcarbazepine) and lamotrigine. Pre-conception counselling should be available to all women with epilepsy who are considering pregnancy. Women with epilepsy should be informed about issues relating to the future pregnancy, including methods and consequences of prenatal screening, fertility, genetics of their seizure disorder, teratogenicity of AEDs, folic acid and vitamin K supplements, labour, breast feeding and care of a child. During pregnancy, the lowest effective dose of the most appropriate AED should be used, aiming for monotherapy where possible. Recent pregnancy databases have suggested that valproate is significantly more teratogenic than carbamazepine, and the combination of valproate and lamotrigine is particularly teratogenic. Most pregnancies in women with epilepsy are without complications, and the majority of infants are delivered healthy with no increased risk of obstetric complications in women. There is no medical reason why a woman with epilepsy cannot breastfeed her child. The AED concentration profiled in breast milk follows the plasma concentration curve. The total amount of drug transferred to infants via breast milk is usually much smaller than the amount transferred via the placenta during pregnancy. However, as drug elimination mechanisms are not fully developed in early infancy, repeated administration of a drug such as lamotrigine via breast milk may lead to accumulation in the infant. Studies have suggested that women with epilepsy are at increased risk of fractures, osteoporosis and osteomalacia. No studies have been undertaken looking at preventative therapies for these co-morbidities.

Antiepileptic drug interactions

INTRODUCTION

Antiepileptics are drugs used in the long-term treatment of epilepsy and other conditions such as pain or psychiatric diseases. They are often administered as polytherapy or in combination with other treatments. It is therefore important to know their potential interactions (with each other and with other substances) in order to avoid altering their efficacy or potentiating their side effects.

OBJECTIVE

The purpose of this article is to review these aspects and stress the most important interactions in day-to-day clinical practice.

RESULTS

Older antiepileptic drugs (AEDs) such as phenytoin, carbamazepine, phenobarbital and valproic acid can significantly interfere not only with each other and other AEDs, but also with other treatments. Although newer AEDs have a more favourable pharmacokinetic profile, they are not entirely exempt from interactions and they are also commonly administered in combination with older AEDs. Another aspect that should be considered is the existence of any clinically important pharmacokinetic and pharmacodynamic interactions in patients requiring the continuous administration of other treatments.

CONCLUSION

We must be aware of the pharmacokinetic and pharmacodynamic interactions of AEDs. Because of a lack of significant interactions, drugs such as levetiracetam, gabapentin or pregabalin can be recommended in particular groups such as patients with cancer, transplants, anticoagulant treatments or HIV infection. In all cases, it is important to ensure AED efficacy and prevent serious complications.

Medications in pregnancy and lactation: part 1. Teratology

One of the least-developed areas of clinical pharmacology and drug research is the use of medication during pregnancy and lactation. This article is the first in a two-part series designed to familiarize physicians with many aspects of the drugs they commonly prescribe for pregnant and breast-feeding women. Almost every pregnant woman is exposed to some type of medication during pregnancy. Although the majority of pregnant and breast-feeding women consume clinically indicated or over-the-counter drug preparation regularly, only few medications have specifically been tested for safety and efficacy during pregnancy. There is scant information on the effect of common pregnancy complications on drug clearance and efficacy. Often, the safety of a drug for mothers, their fetuses, and nursing infants cannot be determined until it has been widely used. Absent this crucial information, many women are either refused medically important agents or experience potentially harmful delays in receiving drug treatment. Conversely, many drugs deemed "safe" are prescribed despite evidence of possible teratogenicity. Novel research and diagnostic applications evolving from the opportunities presented by the advances in genomics and proteomics are now beginning to affect clinical diagnosis, vaccine development, drug discovery, and unique therapies in a modern diagnostic-therapeutic framework-part of the new scientific field of theranostics. This review critically explores a number of recently raised issues in regard to the use of several classes of medications during gestation and seeks to provide a general and concise resource on drugs commonly used during pregnancy and lactation. It also seeks to make clinicians more aware of the controversies surrounding some drugs in an effort to encourage safer prescribing practices through consultation with a maternal-fetal medicine specialist and through references and Web sites that list up-to-date information.

Hormonal contraception and HIV-positive women: metabolic concerns and management strategies

As HIV-positive women live longer lives, and as testing for HIV becomes more routine, clinicians can expect to see more HIV-positive women in their practices. The need to be aware of management issues particular to this population becomes increasingly important. Metabolic dysregulation is a common, long-term complication associated with HIV and is one of the most difficult to manage. Hormonal contraception also is associated with metabolic dysregulation. As more HIV-positive women choose long-term, reversible contraception, the potential for concomitant and additive side effects, and the need for careful, proactive management strategies to avoid these complications, will become more important. This article reviews research detailing the metabolic dysfunction associated with hormonal contraception and with HIV-seropositivity. It highlights reasons for concern regarding the potential, although as yet theoretical, increased risk for metabolic dysfunction when hormonal contraception is used in the presence of HIV. Suggestions for management strategies for women living with HIV who choose to use hormonal contraception are presented. These strategies should be viewed as suggestions for management until substantitive research becomes available.

Pregnancy, epilepsy, and anticonvulsants

The majority of epileptic disorders are not self-limiting over time, and therefore require a long-lasting and often even lifelong antiepileptic drug (AED) treatment, in Wi/omen with epilepsy, the influence of their disease on the possibility and course of pregnancies, as well as the potential impact of the AED treatment on mother and child, are crucial questions.

This review addresses the clinically relevant knovledge concerning the impact of the disease itself and the AED treatment on fertility, pregnancy, delivery, the postpartum period, and teratogenicity. Some of the new AEDs appear to have a favorable profile due to a lack of clinically relevant interactions and promising teratogenic profiles. However, the finding of decreases in lamotrigine serum concentrations during hormonal contraception and pregnancy is an instructive example, shovt/ing that ongoing studies are urgently needed to further investigate stillunanswered questions. Several prospective multinational surveys are currently being performed, and should add essential information in this context.

Epilepsy in women: special considerations for adolescents

Adolescence is a time of many changes. It is a time of growing independence, physical and emotional change, accompanied by social insecurity. Girls tend to enter puberty ahead of their male peers, growing and changing physically. Our culture tells adolescents that they are still immature, but their bodies are saying otherwise. The adolescents are also becoming aware of themselves as individuals, separate from their parents, and are presented with the challenges of independent thinking and action. If, in the midst of all of these changes, an adolescent is given the diagnosis of a chronic disease such as epilepsy, there is an additional burden. Often the adolescent must go through a variety of emotions, including shame, denial, anger, and sadness. Our role as medical providers is to provide some perspective to the illness and help guide our adolescent patient through the tumultuous emotions of grieving and acceptance. We must provide a foundation of assistance and emotional support, as well as medical knowledge. With a firm but compassionate hand, we can help them cope with their disorder. In this chapter, Drs. Haut and Zupanc explore some of the unique considerations in adolescent women with epilepsy. The first part of the chapter deals with the epidemiologic diagnosis of epilepsy in adolescence, the effect of epilepsy on reproductive health, hormonal influences on epilepsy (including catamenial seizures), and the effects of antiepileptic drugs (AEDs) on hormones, contraception, and bone health. In the second part of the chapter, we deal with the very real psychosocial issues and comorbidities of epilepsy, including quality of life, school performance, depression, migraine headaches, social stigma, and lifestyle changes. In the final section, the authors suggest strategies for clinical patient management.

Oxcarbazepine in neuropathic pain

Neuropathic pain is a frequent condition that can result from a variety of underlying conditions and is frequently chronic and difficult to treat. A number of drugs are used to treat neuropathic pain, including anticonvulsants and antidepressants. Oxcarbazepine, a recently introduced antiepileptic drug, was found to possess antineuralgic properties in animal models of neuropathic pain. Several double-blind, placebo-controlled trials have evaluated oxcarbazepine in painful diabetic neuropathy and trigeminal neuralgia. There is good evidence that oxcarbazepine is effective in relieving the pain associated with trigeminal neuralgia. Its efficacy in treating painful diabetic neuropathy is less clear; however, it seems to be useful when tolerated at doses of 1800 mg/day.

Women with epilepsy: hormonal issues from menarche through menopause

Epilepsy is a multilayered disorder complicated by numerous comorbid conditions and hormonal changes. More than 1.5 million girls and women with epilepsy face side effects that are compounded at different ages by menstruation, fertility, pregnancy, fetal health, bone health, and other health issues. Changes in hormonal balance during maturation, from menarche through menopause, affect seizure thresholds and antiepileptic drugs, and vice versa. This overview provides physicians with a background on the multiple issues relevant to women of all ages in the reproductive years, including those planning to conceive and those who are pregnant, and beyond the childbearing years.

Current approaches to the use of generic antiepileptic drugs

Generic substitution is encouraged as a cost containment strategy for the management of health care resources. However, in epilepsy, the consequences of loss of symptom control are important, and antiepileptic drugs have narrow therapeutic indices. For this reason, generic substitution may be problematic, and certain health authorities have excluded antiepileptic drugs from overall policy recommendations on generic prescribing. The absence of bioequivalence data among generic forms and the relatively broad criteria for bioequivalence with the branded drug allow differences in drug exposure to arise that may be clinically relevant and necessitate monitoring of plasma levels when switching formulations to avoid loss of seizure control or emergence of side effects. Management of these issues carries a significant cost, which should be weighed carefully against the cost savings acquired when purchasing the drug. Both physicians and patients have a right to be informed and approve before pharmacists make a generic substitution or switch between generics.

A new look at the second-generation antiepileptic drugs: a decade of experience

OBJECTIVE

To review data from the literature regarding the efficacy and tolerability of the second-generation antiepileptic drugs which were approved by the Food and Drug Administration (FDA) since 1994.

METHODS

A MEDLINE search of the literature, as well as review of bibliographies, was performed to identify randomized controlled trials and other reports evaluating efficacy, pharmacokinetic profile, adverse effects, and drug interactions of the second-generation antiepileptic drugs. Key search terms included felbamate, gabapentin, lamotrigine, topiramate, tiagabine, levetiracetam, oxcarbazepine, zonisamide, and pregabalin.

RESULTS

Each of the second-generation antiepileptic drugs has demonstrated statistically significant reductions in seizure frequency over baseline compared with placebo or active control. Limited studies of efficacy of the new agents compared with the traditional antiepileptic drugs found no significant differences. Each of the second-generation antiepileptic drugs has a unique pharmacokinetic and side-effect profile. Compared with the traditional agents, the second-generation antiepileptic drugs have fewer serious adverse effects, as well as drug interactions.

CONCLUSION

Knowledge of the second-generation antiepileptic drugs has greatly expanded over the past decade. The newer agents offer many options in the treatment of epilepsy that are safe, efficacious, and well tolerated.

Thirty years of clinical experience with carbamazepine in the treatment of bipolar illness: principles and practice

Carbamazepine began to be studied in a systematic fashion in the 1970s and became more widely used in the treatment of bipolar disorder in the 1980s. Interest in carbamazepine has been renewed by (i) the recent US FDA approval of a long-acting preparation for the treatment of acute mania; (ii) studies suggesting some efficacy in bipolar depression; and (iii) evidence of prophylactic efficacy in some difficult-to-treat subtypes of bipolar illness. A series of double-blind controlled studies of the drug were conducted at the US National Institute of Mental Health from the mid-1970s to the mid-1990s. This review summarises our experience in the context of the current literature on the clinical efficacy, adverse effects and pharmacokinetic interactions of carbamazepine. Carbamazepine has an important and still evolving place in the treatment of acute mania and long-term prophylaxis. It may be useful in individuals with symptoms that are not responsive to other treatments and in some subtypes of bipolar disorder that are not typically responsive to a more traditional agent such as lithium. These subtypes might include those patients with bipolar II disorder, dysphoric mania, substance abuse co-morbidity, mood incongruent delusions, and a negative family history of bipolar illness in first-degree relatives. In addition, carbamazepine may be useful in patients who do not adequately tolerate other interventions as a result of adverse effects, such as weight gain, tremor, diabetes insipidus or polycystic ovarian syndrome. We review our clinical and research experience with carbamazepine alone and in combination with lithium, valproic acid and other agents in complex combination treatment of bipolar illness. More precise clinical and biological predictors and correlates of individual clinical responsiveness to carbamazepine and other mood stabilisers are eagerly awaited.

Oral Contraceptives Induce Lamotrigine Metabolism: Evidence from a Double-blind, Placebo-controlled Trial

PURPOSE

This study evaluates the effect of oral contraceptives on lamotrigine (LTG) plasma concentrations and urine excretion of LTG metabolites in a double-blind, placebo-controlled, crossover study in patients with epilepsy.

METHODS

Women with epilepsy, treated with LTG in monotherapy and taking combination-type oral contraceptives, were randomized to treatment with placebo or a standard combination-type contraceptive pill. The dose-corrected trough plasma concentration of LTG and the ratio of N-2-glucuronide/unchanged LTG on urine after 21 days of concomitant placebo treatment was analyzed versus those after 21 days of concomitant treatment with the oral contraceptive pill.

RESULTS

The mean dose-corrected LTG concentration after placebo treatment was 84%[95% confidence interval (CI), 45-134%] higher than after oral contraceptives, signifying an almost doubling of the concentration after cessation of oral contraceptives. Most of this increase took place within the first week after oral contraceptives were stopped. The N-2-glucuronide/LTG ratio in the urine was decreased by 31% (95% CI, -20-61%) when shifting from oral contraceptives to placebo.

CONCLUSIONS

Cessation of oral contraceptives leads to an 84% increase in the concentration of LTG. In parallel, the excretion of the N-2-glucuronide was decreased, indicating that the changes are caused by altered LTG glucuronidation. The change in LTG concentrations was observed within 1 week of the shift of treatment, suggesting that induction and deinduction of LTG glucuronidation is faster than that seen for other metabolic pathways (e.g., cytochrome P450).

Pharmacokinetics and interactions of headache medications, part II: prophylactic treatments

The present part II review highlights pharmacokinetic drug-drug interactions (excluding those of minor severity) of medications used in prophylactic treatment of the main primary headaches (migraine, tension-type and cluster headache). The principles of pharmacokinetics and metabolism, and the interactions of medications for acute treatment are examined in part I. The overall goal of this series of two reviews is to increase the awareness of physicians, primary care providers and specialists regarding pharmacokinetic drug-drug interactions (DDIs) of headache medications. The aim of prophylactic treatment is to reduce the frequency of headache attacks using beta-blockers, calcium-channel blockers, antidepressants, antiepileptics, lithium, serotonin antagonists, corticosteroids and muscle relaxants, which must be taken daily for long periods. During treatment the patient often continues to take symptomatic drugs for the attack, and may need other medications for associated or new-onset illnesses. DDIs can, therefore, occur. As a whole, DDIs of clinical relevance concerning prophylactic drugs are a limited number. Their effects can be prevented by starting the treatment with low dosages, which should be gradually increased depending on response and side effects, while frequently monitoring the patient and plasma levels of other possible coadministered drugs with a narrow therapeutic range. Most headache medications are substrates of CYP2D6 (e.g., beta-blockers, antidepressants) or CYP3A4 (e.g., calcium-channel blockers, selective serotonin re-uptake inhibitors, corticosteroids). The inducers and, especially, the inhibitors of these isoenzymes should be carefully coadministered.

Prioritizing children's medicines for research: a pharmaco-epidemiological study of antiepileptic drugs

AIMS

To investigate the prescribing epidemiology, in UK primary care, of newer antiepileptic drugs (AEDs) compared with conventional AEDs and to identify AEDs for further research in response to the European Medicines Agency report on epilepsy.

METHODS

Subjects aged 0-18 years, from the UK General Practice Research Database, who were prescribed an AED between 1993 and 2005. Prescribing prevalence and incidence, stratified by age and AED, were calculated.

RESULTS

A total of 7721 subjects were included and 70% were prescribed one drug. Overall prescribing prevalence for all AEDs had increased by 19%. The prevalence (95% confidence interval) of newer AED prescribing had increased fivefold from 0.67 (0.58, 0.76) to 3.20 (3.03, 3.37) per 1000 person-years. Conversely, the prevalence of conventional AEDs had declined by 17% from 6.63 (6.34, 6.92) per 1000 person-years to 5.51 (5.28, 5.73). Lamotrigine had 65% of newer AED prescriptions and was the most prescribed newer drug for both the 2-11 years and 12-18 years age groups with prevalences of 1.47 and 2.55 per 1000 person-years, respectively.

CONCLUSIONS

There is a rapid increase in newer AED prescribing to children and adolescents in UK primary care, while prescribing of conventional AEDs is declining. Since 1997, the prevalence of vigabatrin has fallen, coinciding with the UK safety warnings on visual field defects. The uptake of lamotrigine, topiramate and levetiracetam is rapid and as the safety of these drugs has not been established, they should be prioritized for further research. Following concerns with vigabatrin, long-term safety surveillance of all newer AEDs is strongly recommended.

Currently available antiepileptic drugs

Many new antiepileptic drugs (AEDs) have become available over the past 15 years. At the same time, the emphasis on treating patients with epilepsy has grown from stopping seizures to avoiding side effects and maximizing quality of life. This review summarizes currently available AEDs, and presents general treatment principles and guidelines for AED selection. Unfortunately, despite the increased treatment options of today, seizure freedom without side effects remains unattainable for too many patients with epilepsy. Consequently, there remains a significant need for further development of new therapies.

Progress report on new antiepileptic drugs: a summary of the Eigth Eilat Conference (EILAT VIII)

The Eigth Eilat Conference on New Antiepileptic Drugs (AEDs)-EILAT VII, took place in Sitges, Barcelona from the 10th to 14th September, 2006. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference, whose main themes included a focus on status epilepticus (epidemiology, current and future treatments), evidence-based treatment guidelines and the potential of neurostimulation in refractory epilepsy. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on marketed AEDs introduced since 1989. This article summarizes the information presented on drugs in development, including brivaracetam, eslicarbazepine acetate (BIA-2-093), fluorofelbamate, ganaxolone, huperzine, lacosamide, retigabine, rufinamide, seletracetam, stiripentol, talampanel, valrocemide, JZP-4, NS1209, PID and RWJ-333369. Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine and new extended release oxcarbazepine formulations, pregabalin, tiagabine, topiramate, vigabatrin, zonisamide and new extended release valproic acid formulations, and the antiepileptic vagal stimulator device are also presented.

The pharmacokinetic and pharmacodynamic consequences of the co-administration of lamotrigine and a combined oral contraceptive in healthy female subjects

AIMS

To assess the pharmacokinetic and pharmacodynamic effects of co-administration of a combined oral contraceptive (ethinyloestradiol plus levonorgestrel) and lamotrigine.

METHODS

Over a period of 130 days, healthy female subjects took lamotrigine (titrated up to 300 mg day(-1)) and the combined oral contraceptive, either individually or as co-therapy. Plasma ethinyloestradiol and levonorgestrel concentrations were measured in the presence and absence of lamotrigine, and serum lamotrigine concentrations were measured in the presence and absence of the combined oral contraceptive. Serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, oestradiol and sex hormone binding globulin were also determined.

RESULTS

Of the 22 enrolled subjects, 16 had evaluable pharmacokinetic data. The mean (90% CI) ratios of lamotrigine area under the concentration-time curve from 0 to 24 h (AUC(0,24 h)) and maximum observed concentration (C(max)) of lamotrigine when it was given with the combined oral contraceptive and during monotherapy were 0.48 (0.44, 0.53) and 0.61 (0.57, 0.66), respectively. Ethinyloestradiol pharmacokinetics were unchanged by lamotrigine, the mean combined oral contraceptive + lamotrigine : combined oral contraceptive alone ratios (90% CI) of the AUC(0,24 h) and C(max) of levonorgestrel were 0.81 (0.76, 0.86) and 0.88 (0.82, 0.93), respectively. FSH and LH concentrations were increased (by 4.7-fold and 3.4-fold, respectively) in the presence of lamotrigine, but the low serum progesterone concentrations suggested that suppression of ovulation was maintained. Intermenstrual bleeding was reported by 7/22 (32%) of subjects during co-administration of lamotrigine and combined oral contraceptive.

CONCLUSIONS

A clinically relevant pharmacokinetic interaction was observed during co-administration of a combined oral contraceptive and lamotrigine. A dosage adjustment for lamotrigine may need to be considered when these agents are co-administered. A modest decrease in the plasma concentration of levonorgestrel was also observed but there was no corresponding hormonal evidence of ovulation.

Increased Apparent Oral Clearance of Valproic Acid during Intake of Combined Contraceptive Steroids in Women with Epilepsy

PURPOSE

To determine potential changes in total and unbound serum valproic acid (VPA) concentrations at steady-state during a cycle of intake of combined hormonal contraceptive (HC) steroids.

METHODS

Blood samples were collected from nine women stabilized on VPA monotherapy on two separate randomized occasions: (i) at the end of the 4- to 7-day HC-free interval, and (ii) on the last day of the HC intake period. Trough concentrations of VPA in serum and serum ultrafiltrates were determined by fluorescence polarization immunoassay.

RESULTS

In all women, total and unbound VPA concentrations were higher during the HC-free interval than during HC intake (means +/- SD: 425 +/- 184 vs. 350 +/- 145 micromol/L, respectively, for total VPA, p = 0.002, and 55 +/- 37 vs. 39 +/- 25 micromol/L, respectively, for unbound VPA, p = 0.005). Compared with the HC-free interval, HC intake was associated with a mean 21.5% increase in VPA total apparent oral clearance (from 8.0 +/- 5.2 to 9.7 +/- 6.4 ml/h/kg, p = 0.01) and a 45.2 % increase in VPA unbound apparent oral clearance (from 79 +/- 81 to 115 +/- 121 ml/h/kg, p = 0.029).

CONCLUSIONS

The apparent oral clearance of total and unbound VPA increases during the HC intake period compared with the HC-free interval, probably due to induction of glucuronosyltransferase by ethinylestradiol. The magnitude of the change varies across individuals, being potentially clinically relevant in some cases. Serum VPA concentrations should be monitored when adding or discontinuing HC steroids, and possibly during the on-off intervals of a HC cycle.

Clinically relevant drug interactions with antiepileptic drugs

Some patients with difficult-to-treat epilepsy benefit from combination therapy with two or more antiepileptic drugs (AEDs). Additionally, virtually all epilepsy patients will receive, at some time in their lives, other medications for the management of associated conditions. In these situations, clinically important drug interactions may occur. Carbamazepine, phenytoin, phenobarbital and primidone induce many cytochrome P450 (CYP) and glucuronyl transferase (GT) enzymes, and can reduce drastically the serum concentration of associated drugs which are substrates of the same enzymes. Examples of agents whose serum levels are decreased markedly by enzyme-inducing AEDs, include lamotrigine, tiagabine, several steroidal drugs, cyclosporin A, oral anticoagulants and many cardiovascular, antineoplastic and psychotropic drugs. Valproic acid is not enzyme inducer, but it may cause clinically relevant drug interactions by inhibiting the metabolism of selected substrates, most notably phenobarbital and lamotrigine. Compared with older generation agents, most of the recently developed AEDs are less likely to induce or inhibit the activity of CYP or GT enzymes. However, they may be a target for metabolically mediated drug interactions, and oxcarbazepine, lamotrigine, felbamate and, at high dosages, topiramate may stimulate the metabolism of oral contraceptive steroids. Levetiracetam, gabapentin and pregabalin have not been reported to cause or be a target for clinically relevant pharmacokinetic drug interactions. Pharmacodynamic interactions involving AEDs have not been well characterized, but their understanding is important for a more rational approach to combination therapy. In particular, neurotoxic effects appear to be more likely with coprescription of AEDs sharing the same primary mechanism of action.

Management of epilepsy in women of childbearing age: practical recommendations

Women with epilepsy should not be discouraged from becoming pregnant as the likelihood of having a healthy baby is very high. However, in such women, early and individualised counselling about pregnancy and contraception is essential. Ideally, pregnancies should be planned, folic acid (5 mg/day) given and antiepileptic drug (AED) treatment optimised well before conception to ensure that the lowest dosage that controls seizures is administered. When initiating AEDs in a woman of childbearing age, the most appropriate drug for the seizure type and syndrome should be chosen, although it is preferable to avoid valproate, because of a possible elevated risk of fetal malformations, when equi-effective agents are available for a given syndrome. In women who become pregnant while taking AEDs, fetal monitoring should include high-resolution ultrasonography before week 20 and measurement of serum alpha-fetoprotein levels. Amniocentesis is not routinely indicated. The measurement of blood concentrations of AEDs can be useful to ensure that the lowest possible maintenance dosage is being used, especially for those drugs whose pharmacokinetics are likely to change during pregnancy. Breastfeeding should be encouraged whatever the treatment administered.

Sexual dysfunction in patients with epilepsy: communication strategies and assessment tools

Sexual dysfunction is common among patients with epilepsy, but many clinicians do not include inquiries about this aspect of the patient's health in their routine evaluations. This article presents approaches for taking a sexual history and for discussing sexual problems. The utility of standardized sexual dysfunction questionnaires is reviewed and the important elements of appropriate and effective counseling are highlighted.

The impact of antiepileptic drug therapy on steroidal contraceptive efficacy

Women with epilepsy face unique challenges in maintaining steroidal contraceptive efficacy because some antiepileptic drugs (AEDs) increase the rate of hepatic metabolism of contraceptive steroids, leading to higher potential for contraceptive failure in this population. Planned pregnancy is of great clinical and social importance for women with epilepsy because of the increased risk of birth defects from fetal exposure to AEDs. Current clinical guidelines for contraceptive management in women with epilepsy provide misleading information by focusing on the estrogen content of the formulation, which regulates the menstrual cycle, rather than on the progestin content of the formulation, which provides contraceptive efficacy. This article reviews studies of AED-contraceptive interaction and misconceptions about maintaining contraceptive efficacy and makes recommendations for contraceptive management in women with epilepsy who receive concomitant AED therapy.

Synthetic drugs and natural products as modulators of constitutive androstane receptor (CAR) and pregnane X receptor (PXR)

Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are members of the nuclear receptor superfamily. These transcription factors are predominantly expressed in the liver, where they are activated by structurally diverse compounds, including many drugs and endogenous substances. CAR and PXR regulate the expression of a broad range of genes, which contribute to transcellular transport, bioactivation, and detoxification of numerous xenochemicals and endogenous substances. This article discusses the importance of these receptors for pharmacology and toxicology, emphasizing the role of individual drugs and natural products as agonists, indirect activators, inverse agonists, and antagonists of CAR and PXR.

Clinical experience with topiramate dosing and serum levels in patients with epilepsy

OBJECTIVE

To investigate the relevance of serum topiramate (TPM) levels (SL) monitoring in the clinical management of epileptic patients.

METHODS

Twenty-seven patients with different epileptic syndromes on TPM therapy were studied. TPM was used as add-on in 26 patients, only in one as monotherapy de novo; one case changed from TPM as add-on to TPM monotherapy. The mean follow-up time was 11 months. TPM SL were measured by fluorescence polarization immunoassay.

RESULTS

We analyzed the TPM SL in 43 samples from 27 patients. Mean TPM dose was 3.9mg/kg, mean TPM SL 13.43mumol/l. The mean level to dose ratio (LDR) was 3.63mumol/l/mg/kg. Four patients became seizure-free, all with TPM dosages lower than the mean. Eleven patients had at least 50% seizure reduction. The comedication with enzyme-inducing AED significantly reduced TPM SL and LDR. On the other hand, the influence of valproic acid (VPA) on TPM LDR was not univocal. Indeed, patients younger than 15 years showed SL values lower than the adults did, although not significant.

CONCLUSION

We could not detect a direct relationship between high TPM SL and efficacy neither between high TPM SL and tolerability. However, the data we collected seem to favour the hypothesis that high TPM dosage and SL might be associated to a greater probability to reduce seizure severity.

Women are not the same as men: specific clinical issues for female patients with bipolar disorder

Women are not the same as men. While this observation can be considered to subjectively manifest in many different ways, objectively a greater tendency for bipolar II disorder, depressive symptoms, a rapid cycling course, and the consequences of being of child-rearing age can all represent additional challenges for female patients. Despite much recent interest in improving the management of patients with bipolar disorder, relatively little guidance exists relating to female-biased gender-specific issues. This review article will explore how female gender can influence bipolar disorder and its treatment and will focus on epidemiologic differences, the relevance to clinical presentation of events unique to women (particularly contraception, pregnancy, and lactation), and the importance of considering gender when making decisions about the pharmacological management of mood. All female patients should receive counseling regarding family planning and sexually transmitted diseases, as well as the risks of and treatment options during pregnancy and postpartum. Wherever possible, treatment choices should be made in a partnership between patient and clinician.

Valproic Acid in Epilepsy

Valproic acid (sodium valproate) is widely used as a first-line antiepileptic agent. As with many antiepileptic drugs, there are a number of consequences associated with the use of valproic acid in women of child-bearing potential. Most pregnancies have a favourable outcome in women with epilepsy, and these women should not be discouraged from becoming pregnant. Unlike many other antiepileptic drugs, valproic acid has no significant pharmacokinetic interactions with the steroid hormones used in oral contraceptives. During pregnancy, the major risks to mother and child result from loss of seizure control on the one hand, and an elevated risk of major congenital malformations due to antiepileptic drug treatment on the other. In particular, an elevated risk of major congenital malformations associated with valproic acid use has been a consistent finding in studies of patient registries and several large case series. In addition, developmental delay, characterised by low verbal IQ, has also been reported in children exposed to valproic acid in utero, although the relative risk is not precisely known. For these reasons, pregnancies in women being treated with valproic acid need to be planned, and the benefit-risk ratios associated with continuing valproic acid or changing treatment need to be discussed with the patient. When treatment with valproic acid is the most appropriate treatment to achieve optimal seizure control, a number of measures can be implemented to minimise risk to the fetus. These include the use of the lowest possible effective dose of valproic acid in monotherapy (ideally <1000 mg/day), appropriate folic acid supplementation and close antenatal monitoring. Regular counselling is a prerequisite for informed planning of pregnancies and optimisation of the probability of a healthy outcome. Future research on valproic acid and pregnancy should involve risk assessment in large, population-based prospective studies.

Canadian Network for Mood and Anxiety Treatments (CANMAT) guidelines for the management of patients with bipolar disorder: consensus and controversies

Since the previous publication of Canadian Network for Mood and Anxiety Treatments (CANMAT) guidelines in 1997, there has been a substantial increase in evidence-based treatment options for bipolar disorder. The present guidelines review the new evidence and use criteria to rate strength of evidence and incorporate effectiveness, safety, and tolerability data to determine global clinical recommendations for treatment of various phases of bipolar disorder. The guidelines suggest that although pharmacotherapy forms the cornerstone of management, utilization of adjunctive psychosocial treatments and incorporation of chronic disease management model involving a healthcare team are required in providing optimal management for patients with bipolar disorder. Lithium, valproate and several atypical antipsychotics are first-line treatments for acute mania. Bipolar depression and mixed states are frequently associated with suicidal acts; therefore assessment for suicide should always be an integral part of managing any bipolar patient. Lithium, lamotrigine or various combinations of antidepressant and mood-stabilizing agents are first-line treatments for bipolar depression. First-line options in the maintenance treatment of bipolar disorder are lithium, lamotrigine, valproate and olanzapine. Historical and symptom profiles help with treatment selection. With the growing recognition of bipolar II disorders, it is anticipated that a larger body of evidence will become available to guide treatment of this common and disabling condition. These guidelines also discuss issues related to bipolar disorder in women and those with comorbidity and include a section on safety and monitoring.

An overview of psychotropic drug-drug interactions

The psychotropic drug-drug interactions most likely to be relevant to psychiatrists' practices are examined. The metabolism and the enzymatic and P-glycoprotein inhibition/induction profiles of all antidepressants, antipsychotics, and mood stabilizers are described; all clinically meaningful drug-drug interactions between agents in these psychotropic classes, as well as with frequently encountered nonpsychotropic agents, are detailed; and information on the pharmacokinetic/pharmacodynamic results, mechanisms, and clinical consequences of these interactions is presented. Although the range of drug-drug interactions involving psychotropic agents is large, it is a finite and manageable subset of the much larger domain of all possible drug-drug interactions. Sophisticated computer programs will ultimately provide the best means of avoiding drug-drug interactions. Until these programs are developed, the best defense against drug-drug interactions is awareness and focused attention to this issue.

Best Practice Guidelines for the Management of Women with Epilepsy

Being a woman with epilepsy is not the same as being a man with epilepsy. Epilepsy affects sexual development, menstrual cycle, aspects of contraception, fertility, and reproduction. MENSTRUAL CYCLE, EPILEPSY, AND FERTILITY: The diagnosis of epilepsy and the use of antiepileptic drugs (AEDs) present women of childbearing age with many problems; both the disease and its treatment can alter the menstrual cycle and fertility. CONTRACEPTION IN EPILEPSY: There are no contraindications to the use of nonhormonal methods of contraception in women with epilepsy (see Table 3). Nonenzyme-inducing AEDs (valproate sodium, benzodiazepines, ethosuximide, and levetiracetam) do not show any interactions with the combined oral contraceptive pill. There are interactions between the COCP and hepatic microsomal-inducing AEDs (phenytoin, barbiturates, carbamazepine, topiramate [doses above 200 mg/day], and oxcarbazepine) and also lamotrigine. SEXUALITY: The majority of women with epilepsy appear to have normal sex lives, although in some women with epilepsy, both the desire and arousal phases may be inhibited. PRECONCEPTION COUNSELING: Preconception counseling should be available to all women with epilepsy who are considering pregnancy. Women with epilepsy should be aware of a number of issues relating to future pregnancy, including methods and consequences of prenatal screening, genetics of their seizure disorder, teratogenicity of AEDs, folic acid and vitamin K supplements, labor, breast feeding, and childcare. PREGNANCY: The lowest effective dose of the most appropriate AED should be used, aiming for monotherapy where possible. Recent pregnancy databases have suggested that valproate is significantly more teratogenic than carbamazepine, and the combination of valproate sodium and lamotrigine is particularly teratogenic. Most pregnancies are uneventful in women with epilepsy, and most babies are delivered healthy with no increased risk of obstetric complications in women. BREAST FEEDING: All women with epilepsy should be encouraged to breastfeed their babies. The AED concentration profiled in breast milk follows the plasma concentration curve. The total amount of drug transferred to infants via breast milk is usually much smaller than the amount transferred via the placenta during pregnancy. However, as drug elimination mechanisms are not fully developed in early infancy, repeated administration of a drug such as lamotrigine via breast milk may lead to accumulation in the infant. THE CARE OF CHILDREN OF MOTHERS WITH EPILEPSY: Although there is much anxiety about the possible risks to a child from the mother's epilepsy, there is little published evidence. The risk of the child being harmed depends on the type of seizure and its severity and frequency, and this risk is probably small if time is taken to train mothers and caregivers in safety precautions. MENOPAUSE: During menopause, about 40% of women report worsening of their seizure disorder, 27% improve, and a third had no change. Hormone replacement therapy is significantly associated with an increase in seizure frequency during menopause, and this is more likely in women with a history of catamenial epilepsy. BONE HEALTH: Women with epilepsy are at increased risk of fractures, osteoporosis, and osteomalacia.

Clinical characteristics and management of bipolar disorder in women across the life span

Though prevalent in both genders, specific consideration needs to be given when treating a woman suffering from bipolar disorder over her lifetime. Bipolar disorder is a serious and incapacitating illness affecting an estimated 5% of women. The first episode of illness in women is usually a depressive episode. Female gender has been associated with greater axis-one comorbidity, more depressive episodes, rapid cycling and mixed affective states. Special consideration is required for the treatment of bipolar disorder during reproductive events. More studies are required to better understand the course, outcome and gender-specific treatment strategies of this disorder.

Safety and tolerability of emerging pharmacological treatments for bipolar disorder

OBJECTIVES

Over the past few years numerous new agents have been examined for their efficacy in bipolar disorder (BPD). New antiepileptic agents and atypical antipsychotics currently form the bulk of these emerging agents. As the armamentarium for treating BPD increases, it allows for the possibility of choosing drugs on the basis of their tolerability as well as their efficacy, rather than on efficacy alone.

METHODS

Efficacy data for newer antiepileptic drugs (lamotrigine, topiramate, gabapentin, oxcarbazepine) and atypical antipsychotics (olanzapine, clozapine, risperidone, quetiapine, ziprasidone, aripiprazole) are briefly reviewed. The article focuses on relative safety and tolerability of these agents.

RESULTS

In general, most of these newer agents have better side effect and tolerability profiles than older agents commonly used to treat BPD (lithium, valproate, carbamazepine); however, these must be weighed against efficacy demonstrated to date in randomized, controlled trials. Cognitive impairment is a concern with topiramate, weight gain and risk of diabetes with some of the atypical antipsychotic agents, and rash with lamotrigine.

CONCLUSIONS

Side effects of newer emerging agents for the treatment of BPD can be effectively managed and the risks reduced by instituting practical strategies early in management.

FFPRHC Guidance (July 2005): The use of contraception outside the terms of the product licence

This Guidance provides information for clinicians and women considering the use of contraception outside the terms of the product licence. A key to the grades of recommendations, based on levels of evidence, is given at the end of this document. Details of the methods used by the Clinical Effectiveness Unit (CEU) in developing this Guidance and evidence tables summarising the research basis of the recommendations are available on the Faculty website (www.ffprhc.org.uk). Abbreviations (in alphabetical order) used include: CEU, Clinical Effectiveness Unit; COC, combined oral contraception/contraceptive; DMPA, depot medroxyprogesterone acetate; ENG, etonogestrel; IUD, copper-bearing intrauterine contraceptive device; LNG-IUS, levonorgestrel-releasing intrauterine system; NET-EN, norethisterone enantate; PGD, Patient Group Direction; PIL, Patient Information Leaflet; POC, progestogen-only contraception/contraceptive; POEC, progestogen-only emergency contraception; POP, progestogen-only pill; RCT, randomised controlled trial; SPC, Summary of Product Characteristics; UPSI, unprotected sexual intercourse; WHO, World Health Organization; WHOMEC, WHO Medical Eligibility Criteria for Contraceptive Use; WHOSPR, WHO Selected Practice Recommendations for Contraceptive Use.

Effect of zonisamide on the pharmacokinetics and pharmacodynamics of a combination ethinyl estradiol-norethindrone oral contraceptive in healthy women

BACKGROUND

Several antiepileptic drugs have clinically significant pharmacokinetic interactions with oral contraceptives (OCs) that may result in contraceptive failure.

OBJECTIVE

The aim of this study was to assess the effect of zonisamide on the pharmacokinetics of the individual components of a combination OC (ethinyl estradiol [EE] 0.035 mg and norethindrone [NOR] 1 mg) and on pharmacodynamic variables that may be increased in the event of reduced contraceptive efficacy (concentrations of serum luteinizing hormone [LH], follicle-stimulating hormone [FSH], and progesterone).

METHODS

This was a single-center, open-label, 1-sequence, crossover study. Healthy, premenopausal women received the combination OC for three 28-day cycles (combination OC for 21 days, followed by placebo for 7 days). Following stabilization on the OC during the first cycle, blood was collected during cycle 2 for the determination of serum EE and NOR profiles (day 14) and serum LH, FSH, and progesterone concentrations (days 13-15). Starting on day 15 of cycle 2, zonisamide was administered orally at 100 mg/d and titrated to a target dose of 400 mg/d. EE and NOR profiles and serum LH, FSH, and progesterone concentrations were obtained again in cycle 3 (in the presence of zonisamide) and compared with those from cycle 2 (in the absence of zonisamide).

RESULTS

Thirty-seven healthy premenopausal women (mean age, 26.1 years [range, 18-51 years]; mean body weight, 65.5 kg [range, 50.4-93.1 kg]; mean height, 165.8 cm [range, 152.4-182.9 cm]) received > or =1 dose of zonisamide. Of the 33 subjects (89.2%) who completed the study, 26 (78.8%) underwent titration to a stable zonisamide dose of 400 mg/d. For EE, the mean (SD) AUC over a 24-hour dosing interval (AUC(tau)) was 1139 (317) pg.h/mL in cycle 2 and 1143 (312) pg.h/mL in cycle 3; the mean C(max) in the respective cycles was 133 (39) and 141 (46) pg/mL. For NOR, the corresponding values were 140 (48) and 159 (46) ng.h/mL for AUC(tau) and 21 (5.4) and 23 (6.7) ng/mL for C(max). The 90% Cls for the geometric mean ratios (cycle 3:cycle 2) for AUC(tau) and C(max) fell within the accepted range for lack of interaction (0.80-1.25). There were no increases in LH, FSH, or progesterone concentrations between cycle 2 and cycle 3.

CONCLUSIONS

In these healthy volunteers, steady-state zonisamide dosing had no clinically significant effect on the pharmacokinetics of EE or NOR. There was no pharmacodynamic evidence that zonisamide is likely to reduce the contraceptive effectiveness of OCs containing EE and NOR.