Drug monitoring of lamotrigine and oxcarbazepine combination during pregnancy

Association of oxcarbazepine concentration with seizure frequency in pregnant women with epilepsy

The management of epilepsy during pregnancy presents particular challenges for neurologists worldwide. Currently, there are no clear recommendations for oxcarbazepine (OXC) specific target concentration during pregnancy. We conducted this retrospective observational cohort study on pregnant women with epilepsy (WWE) who received OXC monotherapy or polytherapy, at the epilepsy outpatient clinic of a tertiary hospital in eastern China. Sixteen pregnancies of 16 WWE were split into the seizure-free group or the non-seizure-free group, according to whether they had been seizure free for more than one year prior to conception or not. There was a significantly decrease in OXC concentration throughout pregnancy, as indicated by the concentration/dose ratio and the ratio of target concentration (RTC). The second trimester of pregnancy was the period when seizure deterioration occurred the most, particularly in the non-seizure-free group. Lower RTC_OXC was identified to be a risk factor for increasing seizure frequency in both the total group and the non-seizure-free group in both univariate and multivariate analysis, with a threshold of 0.575 for differentiating patients at high-risk and low-risk for seizure deterioration. In conclusion, this study suggested an OXC concentration threshold of 0.575 during pregnancy for assisting neurologists in OXC drug monitoring and dose adaptation.

Changes in seizure frequency and anti-seizure medication therapy during pregnancy and one year postpregnancy

Seizure control in women with epilepsy (WWE) during pregnancy is a vital concern. The aim of this study was to compare changes in seizure frequency and anti-seizure medication (ASM ) therapy in WWE in a real-world setting over three epochs (prepregnancy, pregnancy, and postpregnancy). We screened WWE who were pregnant between 1 January 2010 and 31 December 2020 from the epilepsy follow-up registry database of a tertiary hospital in China. We reviewed and collected follow-up data for the following time periods: 12 months before pregnancy (epoch 1), throughout pregnancy and the first 6 weeks postpartum (epoch 2), and from 6 weeks to 12 months postpartum (epoch 3). Seizures were classified into two categories: tonic‒clonic/focal to bilateral tonic‒clonic seizures and non-tonic‒clonic seizures. The main indicator was the seizure-free rate over the three epochs. Using epoch 1 as a reference, we also compared the percentage of women with an increased seizure frequency, as well as changes in ASM treatment, in epochs 2 and 3. Ultimately, 271 eligible pregnancies in 249 women were included. The seizure-free rates in epoch 1, epoch 2, and epoch 3 were 38.4%, 34.7%, and 43.9%, respectively (P = 0.09). The top three ASMs used in the three epochs were lamotrigine, levetiracetam, and oxcarbazepine. Using epoch 1 as a reference, the percentages of women with increased frequencies of tonic‒clonic/focal to bilateral tonic‒clonic seizures in epoch 2 and epoch 3 were 17.0% and 14.8%, respectively, while the percentages of women with an increased frequency of non-tonic‒clonic seizures in epoch 2 and epoch 3 were 31.0% and 21.8% (P = 0.02). The percentage of women whose ASM dosages were increased in epoch 2 was higher than that in epoch 3 (35.8% vs. 27.3%, P = 0.03). The seizure frequency during pregnancy may not differ significantly from that during prepregnancy and postpregnancy if WWE are treated according to the guidelines.

Management of Anti-Seizure Medications during Pregnancy: Advancements in The Past Decade

Management of seizures often involves continuous medication use throughout a patient's life, including when a patient is pregnant. The physiological changes during pregnancy can lead to altered drug exposure to anti-seizure medications, increasing patient response variability. In addition, subtherapeutic anti-seizure medication concentrations in the mother may increase seizure frequency, raising the risk of miscarriage and preterm labor. On the other hand, drug exposure increases can lead to differences in neurodevelopmental outcomes in the developing fetus. Established pregnancy registries provide insight into the teratogenicity potential of anti-seizure medication use. In addition, some anti-seizure medications are associated with an increased risk of major congenital malformations, and their use has declined over the last decade. Although newer anti-seizure medications are thought to have more favorable pharmacokinetics in general, they are not without risk, as they may undergo significant pharmacokinetic changes when an individual becomes pregnant. With known changes in metabolism and kidney function during pregnancy, therapeutic monitoring of drug concentrations helps to determine if and when doses should be changed to maintain similar seizure control as observed pre-pregnancy. This review concentrates on the results from research in the past decade (2010-2022) regarding risks of major congenital malformations, changes in prescribing patterns, and pharmacokinetics of the anti-seizure medications that are prescribed to pregnant patients with epilepsy.

Breastfeeding recommendations for women taking anti-seizure medications

The literature regarding breastfeeding and effects of anti-seizure medication (ASM) exposure on the breastfed infant has been evolving rapidly over the last decade as new studies advance our understanding of the extent of medication exposure via breastfeeding and the long-term developmental outcomes of breastfed infants. Currently, strong evidence supports the safety of breastfeeding for women with epilepsy (WWE) taking most prescribed ASMs. In this review, we present a comprehensive overview of the data regarding ASM exposure in breastfed infants and neurodevelopmental outcomes in breastfed infants of mothers taking various ASMs. In addition, we present current breastfeeding recommendations and the reported adverse effects of various ASMs to facilitate decision making in the clinical care of WWE.

Treatment and care of women with epilepsy before, during, and after pregnancy: a practical guide

Women with epilepsy (WWE) wishing for a child represent a highly relevant subgroup of epilepsy patients. The treating epileptologist needs to delineate the epilepsy syndrome and choose the appropriate anti-seizure medication (ASM) considering the main goal of seizure freedom, teratogenic risks, changes in drug metabolism during pregnancy and postpartum, demanding for up-titration during and down-titration after pregnancy. Folic acid or vitamin K supplements and breastfeeding are also discussed in this review. Lamotrigine and levetiracetam have the lowest teratogenic potential. Data on teratogenic risks are also favorable for oxcarbazepine, whereas topiramate tends to have an unfavorable profile. Valproate needs special emphasis. It is most effective in generalized seizures but should be avoided whenever possible due to its teratogenic effects and the negative impact on neuropsychological development of in utero-exposed children. Valproate still has its justification in patients not achieving seizure freedom with other ASMs or if a woman decides to or cannot become pregnant for any reason. When valproate is the most appropriate treatment option, the patient and caregiver must be fully informed of the risks associated with its use during pregnancies. Folate supplementation is recommended to reduce the risk of major congenital malformations. However, there is insufficient information to address the optimal dose and it is unclear whether higher doses offer greater protection. There is currently no general recommendation for a peripartum vitamin K prophylaxis. During pregnancy most ASMs (e.g. lamotrigine, oxcarbazepine, and levetiracetam) need to be increased to compensate for the decline in serum levels; exceptions are valproate and carbamazepine. Postpartum, baseline levels are reached relatively fast, and down-titration is performed empirically. Many ASMs in monotherapy are (moderately) safe for breastfeeding and women should be encouraged to do so. This review provides a practically oriented overview of the complex management of WWE before, during, and after pregnancy.

Antiseizure Medication Concentrations During Pregnancy: Results From the Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD) Study

IMPORTANCE

During pregnancy in women with epilepsy, lower blood concentrations of antiseizure medications can have adverse clinical consequences.

OBJECTIVE

To characterize pregnancy-associated concentration changes for several antiseizure medications among women with epilepsy.

DESIGN, SETTING, AND PARTICIPANTS

Enrollment in this prospective, observational cohort study, Maternal Outcomes and Neurodevelopmental Effects of Antiepileptic Drugs (MONEAD), occurred from December 19, 2012, to February 11, 2016, at 20 US sites. Enrolled cohorts included pregnant women with epilepsy and nonpregnant control participants with epilepsy. Inclusion criteria were women aged 14 to 45 years, an intelligence quotient greater than 70 points, and, for the cohort of pregnant women, a fetal gestational age younger than 20 weeks. A total of 1087 women were assessed for eligibility; 397 were excluded and 230 declined. Data were analyzed from May 1, 2014, to June 30, 2021.

EXPOSURE

Medication plasma concentrations in women taking monotherapy or in combination with noninteracting medications. The cohort of pregnant women was monitored through 9 months post partum, with similar time points for control participants.

MAIN OUTCOMES AND MEASURES

Dose-normalized concentrations were calculated as total or unbound plasma medication concentrations divided by total daily dose. Phlebotomy was performed during 4 pregnancy study visits and 3 postpartum visits for the pregnant women and 7 visits over 18 months for control participants. The primary hypothesis was to test pregnancy changes of dose-normalized concentrations from nonpregnant postpartum samples compared with those of control participants.

RESULTS

Of the 351 pregnant women and 109 control participants enrolled in MONEAD, 326 pregnant women (median [range] age, 29 [19-43] years) and 104 control participants (median [range] age, 29 [16-43] years) met eligibility criteria for this analysis. Compared with postpartum values, dose-normalized concentrations during pregnancy were decreased by up to 56.1% for lamotrigine (15.60 μg/L/mg to 6.85 μg/L/mg; P < .001), 36.8% for levetiracetam (11.33 μg/L/mg to 7.16 μg/L/mg; P < .001), 17.3% for carbamazepine (11.56 μg/L/mg to 7.97 μg/L/mg; P = .03), 32.6% for oxcarbazepine (11.55 μg/L/mg to 7.79 μg/L/mg; P < .001), 30.6% for unbound oxcarbazepine (6.15 μg/L/mg to 4.27 μg/L/mg; P < .001), 39.9% for lacosamide (26.14 μg/L/mg to 15.71 μg/L/mg; P < .001), and 29.8% for zonisamide (40.12 μg/L/mg to 28.15 μg/L/mg; P < .001). No significant changes occurred for unbound carbamazepine, carbamazepine-10,11-epoxide, and topiramate, although a decrease was observed for topiramate (29.83 μg/L/mg to 13.77 μg/L/mg; P = .18). Additionally, compared with dose-normalized concentrations from control participants, pregnancy dose-normalized median (SE) concentrations decreased significantly by week of gestational age: carbamazepine, -0.14 (0.06) μg/L/mg (P = .02); carbamazepine unbound, -0.04 (0.01) μg/L/mg (P = .01); lacosamide, -0.23 (0.07) μg/L/mg (P < .001); lamotrigine, -0.20 (0.02) μg/L/mg (P < .001); levetiracetam, -0.06 (0.03) μg/L/mg (P = .01); oxcarbazepine, -0.14 (0.04) μg/L/mg (P < .001); oxcarbazepine unbound, -0.11 (0.03) μg/L/mg (P < .001); and zonisamide, -0.53 (0.14) μg/L/mg (P < .001) except for topiramate (-0.35 [0.20] μg/L/mg per week) and carbamazepine-10,11-epoxide (0.02 [0.01] μg/L/mg).

CONCLUSIONS AND RELEVANCE

Study results suggest that therapeutic drug monitoring should begin early in pregnancy and that increasing doses of these anticonvulsants may be needed throughout the course of pregnancy.

Pharmacokinetic changes for newer antiepileptic drugs and seizure control during pregnancy

Objective

To investigate pharmacokinetic changes in newer antiepileptic drugs (AEDs) and assess seizure frequencies and risk factors of increased seizures during pregnancy in women with epilepsy (WWE).

Methods

A total of 56 pregnancies in 53 WWE who received newer antiepileptic drugs (AEDs) were enrolled. Data on seizure activity and types, daily dose, and AEDs blood levels were derived from routine clinical follow‐up. Changes in AEDs clearance were compared between each trimester and nonpregnant baseline. The ratio of AED levels of each trimester to their targets (nonpregnant baseline) concentrations (RTC) was compared between patients with and without an increased seizure. A binary logistic regression was used to investigate the risk factors contributing to seizure worsening during pregnancy.

Results

Increased clearances of LTG, LEV, and OXC were observed in all trimesters versus nonpregnant baseline. The peak changes in the clearance of LTG (3.42‐fold baseline clearance) (p < 0.001) and LEV (2.78‐fold) (p < 0.001) occurred in the second trimester during pregnancy, followed by oxcarbazepine (2.11‐fold) in the third trimester (p < 0.03). Plasma concentrations of LTG and LEV during pregnancy were significantly decreased compared to baseline levels, except for OXC. However, no significant differences in RTC values were observed between patients with and without seizure worsening. Some risk factors as seizures for the prior nine months could significantly affect seizure frequency during pregnancy.

Conclusion

We found substantial changes in the pharmacokinetics of multiple newer AEDs in WWE, reinforcing the need for therapeutic drug monitoring (TDM) during pregnancy. We would encourage at least one monitoring every trimester and probably more frequently for women with poorly seizure control before pregnancy, and AEDs dose adjustment should keep up with clearance changes. In addition, a well‐controlled seizure nine months before pregnancy could lower the risks of seizure during pregnancy, highlighting the importance of pre‐pregnancy counseling and seizure management before pregnancy.

Chronic limbic epilepsy models for therapy discovery: Protocols to improve efficiency

OBJECTIVE

There have been recommendations to improve therapy discovery for epilepsy by incorporating chronic epilepsy models into the preclinical process, but unpredictable seizures and difficulties in maintaining drug levels over prolonged periods have been obstacles to using these animals. We report new protocols in which drugs are administered through a new chronic gastric tube to rats with higher seizure frequencies to minimize these obstacles.

METHODS

Adult rats with spontaneous limbic seizures following an episode of limbic status epilepticus induced by electrical hippocampal stimulation were monitored with long-term video- electroencephalography (EEG). Animals with a predetermined baseline seizure frequency received an intragastric tube for drug administration. Carbamazepine, levetiracetam, phenobarbital, and phenytoin were tested with either an acute protocol (an increasing single dose every other day for a maximum of three doses) or with a chronic protocol (multiple administrations of one dose for a week). Drug levels were obtained to correlate the effect with the level.

RESULTS

With the acute protocol, all four drugs induced a clear dose-related response. Similar dose-related responses were seen following the week-long dosing protocol for carbamazepine, phenobarbital, and phenytoin, and these responses were associated with drug levels that were in the human therapeutic range. The response to chronic levetiracetam was much less robust. The gastric tube route of administration was well tolerated over a number of months.

SIGNIFICANCE

Using rats with stable, higher seizure frequencies made it possible to identify the potential of a drug to suppress seizures in a realistic model of epilepsy with drug levels that are similar to those of human therapeutic levels. The acute protocol provided a full dose response in 1 week. The chronic administration protocol further differentiated drugs that may be effective long term. The gastric tube facilitates a less stressful, humane, and consistent administration of multiple doses.

Population pharmacokinetics of oxcarbazepine: a systematic review

INTRODUCTION

Oxcarbazepine is commonly used as first-line treatment for partial and generalized tonic-clonic seizures. Owing to the high pharmacokinetic variability, several population pharmacokinetic models have been developed for oxcarbazepine to explore potential covariates that affect its pharmacokinetic variation.

AREAS COVERED

This review summarizes the published population pharmacokinetic studies of oxcarbazepine in children and adults available in PubMed and Embase databases. The quality of the retrieved studies was evaluated, and significant covariates that may have an impact on the dosage regimen of oxcarbazepine were explored.

EXPERT OPINION

The pharmacokinetics of oxcarbazepine was founded to be affected by body weight and co-administration with enzyme inducers. Pediatric patients require a higher dose per kilogram than adults because children generally have a higher clearance than adults. Moreover, to maintain the target concentration, patients co-administrate with enzyme inducers need a higher dose than monotherapy due to higher clearance in those patients. Because limited information is available for exposure-response relationship, additional pharmacokinetic/pharmacodynamics investigations of oxcarbazepine need to be conducted to optimize the dosage regimen in clinical practice.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Women with Epilepsy Before, During, and After Pregnancy

During pregnancy, the pharmacokinetics of an antiepileptic drug is altered because of changes in the clearance capacity and volume of distribution. These changes may have consequences for the frequency of seizures during pregnancy and fetal exposure to antiepileptic drugs. In 2009, a review was published providing guidance for the dosing and therapeutic drug monitoring of antiepileptic drugs during pregnancy. Since that review, new drugs have been licensed and new information about existing drugs has been published. With this review, we aim to provide an updated narrative overview of changes in the pharmacokinetics of antiepileptic drugs in women during pregnancy. In addition, we aim to formulate advice for dose modification and therapeutic drug monitoring of antiepileptic drugs. We searched PubMed and the available literature on the pharmacokinetic changes of antiepileptic drugs and seizure frequency during pregnancy published between January 2007 and September 2018. During pregnancy, an increase in clearance and a decrease in the concentrations of lamotrigine, levetiracetam, oxcarbazepine's active metabolite licarbazepine, topiramate, and zonisamide were observed. Carbamazepine clearance remains unchanged during pregnancy. There is inadequate or no evidence for changes in the clearance or concentrations of clobazam and its active metabolite N-desmethylclobazam, gabapentin, lacosamide, perampanel, and valproate. Postpartum elimination rates of lamotrigine, levetiracetam, and licarbazepine resumed to pre-pregnancy values within the first few weeks after pregnancy. We advise monitoring of antiepileptic drug trough concentrations twice before pregnancy. This is the reference concentration. We also advise to consider dose adjustments guided by therapeutic drug monitoring during pregnancy if the antiepileptic drug concentration decreases 15-25% from the pre-pregnancy reference concentration, in the presence of risk factors for convulsions. If the antiepileptic drug concentration changes more than 25% compared with the reference concentration, dose adjustment is advised. Monitoring of levetiracetam, licarbazepine, lamotrigine, and topiramate is recommended during and after pregnancy. Monitoring of clobazam, N-desmethylclobazam, gabapentin, lacosamide, perampanel, and zonisamide during and after pregnancy should be considered. Because of the risk of teratogenic effects, valproate should be avoided during pregnancy. If that is impossible, monitoring of both total and unbound valproate is recommended. More research is needed on the large number of unclear pregnancy-related effects on the pharmacokinetics of antiepileptic drugs.

Closed-loop Neuropharmacology for Epilepsy: Distant Dream or Future Reality?

Epilepsy is considered the most frequent severe neurological condition but most patients treated with medication become seizure free. The management of treatment, however, is highly empirical, mainly relying on observation. A closed-loop therapy for epilepsy would be very valuable for more efficient treatment regimens. Here we discuss monitoring treatment (therapeutic drug monitoring) and the potential developments in this field, as well as providing a review of potential biomarkers that could be used to monitor the disease activity. Finally, we consider the pharmacogenetic input in epilepsy treatment.

Sex, Gender, and Orofacial Pain

This review examines gender prevalence in orofacial pain to elucidate underlying factors that can explain such differences. This review highlights how gender affects (1) the association of hormonal factors and pain modulation; (2) the genetic aspects influencing pain sensitivity and pain perception; (3) the role of resting blood pressure and pain threshold; and (4) the impact of sociocultural, environmental, and psychological factors on pain.

Determination of serum carbamazepine concentration using dried blood spot specimens for resource-limited settings

OBJECTIVES

Carbamazepine (CBZ) is a commonly used anti-epileptic in rural hospitals in India. These hospitals lack the facilities to measure CBZ concentration; however, in larger hospitals this is performed using high performance liquid chromatography (HPLC). Dried blood spot (DBS) represents a feasible matrix for safe transportation by post/courier. This study was to determine whether the concentration of CBZ in serum can be predicted from that measured in DBS using an inexpensive HPLC method and inexpensive standard filter paper.

METHODS

CBZ in serum and DBS from 80 epileptic patients were measured using a validated HPLC assay. The data was then randomly divided into two groups; simple Deming regression was performed with the first group and validation was performed using the second.

RESULTS

There was a good correlation between the serum and DBS concentrations (r = 0.932) in the first group. The regression equation obtained was: predicted serum concentration = DBS concentration x 0.83 + 1.09. In the validation group, the correlation between the predicted and actual serum concentrations was also good (r = 0.958), and the mean difference between them was only 0.28 μg/ml (p = 0.8062). The imprecision and bias in both the groups were acceptable.

CONCLUSION

Using inexpensive materials, serum CBZ concentrations can be accurately predicted from DBS specimens. This method can be recommended for the therapeutic drug monitoring of CBZ in resource-limited settings.

[Pharmacological treatment of women with epilepsy before and during pregnancy]

In the vast majority of women with epilepsy, no complications occur during pregnancy. Important for that is early, preconceptional counseling and close surveillance during pregnancy. The aim should be to maintain the best possible seizure control without occurrence of generalized tonic-clonic seizures while using antiepileptic drugs and with the lowest possible risk of malformations. The warnings for the prescription of valproic acid in women of reproductive age were tightened because of the dose-dependent increase in the malformation rate and other risks, especially regarding adverse effects on childhood cognitive development. The pharmacokinetics of antiepileptic drugs in pregnancy require monitoring of serum drug levels and an early dose adjustment. Breastfeeding should be encouraged in women with epilepsy taking antiepileptic drugs as long as infants are closely monitored with respect to possible sedation and poor drinking.

[Psychopharmacotherapy during pregnancy : Which antipsychotics, tranquilizers and hypnotics are suitable?]

BACKGROUND

When administering psychotropic drugs during pregnancy not only the potential teratogenic effects on the child must be addressed but also the fetotoxic implications for pregnancy and/or the peripartum phase as well as possible neurocognitive developmental disorders must be considered.

OBJECTIVE

Evaluation of the risks and benefits of administering psychotropic drugs during pregnancy or for women who wish to become pregnant.

METHODS

The literature has been reviewed with the purpose of providing information on psychotropic drugs which can safely be administered during pregnancy. The review considers antipsychotics as well as tranquilizers and hypnotics.

RESULTS

Data are available for a multitude of psychotropic drugs that allow a safe estimation on their suitability for use during pregnancy.

CONCLUSION

When treating mental illnesses during pregnancy the option of administering drugs must not principally be ruled out. What is required is an individual assessment of benefits and risks. The risk of an untreated mental illness versus the benefit of a suitable treatment, which may include the use of medication and the potential harm to the infant must be evaluated. If certain rules are observed and a suitable drug is selected the risk to the newborn child and/or mother during pregnancy can be minimized. During pregnancy, therapeutic drug monitoring is indicated and increases the safety for use of drugs and preventing harm to both mother and infant.

Basic obstetric pharmacology

Pregnancy is associated with a variety of physiological changes that can alter the pharmacokinetics and pharmacodynamics of several drugs. However, limited data exists on the pharmacokinetics and pharmacodynamics of the majority of the medications used in pregnancy. In this article, we first describe basic concepts (drug absorption, bioavailability, distribution, metabolism, elimination, and transport) in pharmacokinetics. Then, we discuss several physiological changes that occur during pregnancy that theoretically affect absorption, distribution, metabolism, and elimination. Further, we provide a brief review of the literature on the clinical pharmacokinetic studies performed in pregnant women in recent years. In general, pregnancy increases the clearance of several drugs and correspondingly decreases drug exposure during pregnancy. Based on current drug exposure measurements during pregnancy, alterations in the dose or dosing regimen of certain drugs are essential during pregnancy. More pharmacological studies in pregnant women are needed to optimize drug therapy in pregnancy.

Dried blood spot analysis to assess medication adherence and to inform personalization of treatment

Little research using dried blood spot samples to assess adherence to medication has been reported. The World Health Organisation estimates that only half of the patients in the developed world take their medication as prescribed. Additional costs to the healthcare provider include wasted medicines, avoidable additional hospital visits and non-optimum patient care. There is little evidence of information concerning medication adherence being made available to inform clinical decision making. In this article we explore the potential of the dried blood spot sample collection methodology as a means of identifying medication adherence to facilitate medicines optimization for a range of disparate diseases. Furthermore, the opportunity to personalize healthcare for different patients by assessing the clinically necessary therapeutic level of the relevant drugs is highlighted.

Population pharmacokinetics modeling of oxcarbazepine to characterize drug interactions in Chinese children with epilepsy

AIM

To develop a population pharmacokinetics model of oxcarbazepine in Chinese pediatric patients with epilepsy, and to study the interactions between oxcarbazepine and other antiepileptic drugs (AEDs).

METHODS

A total of 688 patients with epilepsy aged 2 months to 18 years were divided into model (n=573) and valid (n=115) groups. Serum concentrations of the main active metabolite of oxcarbazepine, 10-hydroxycarbazepine (MHD), were determined 0.5-48 h after the last dosage. A population pharmacokinetics (PPK) model was constructed using NLME software. This model was internally evaluated using Bootstrapping and goodness-of-fit plots inspection. The data of the valid group were used to calculate the mean prediction error (MPE), mean absolute prediction error (MAE), mean squared prediction error (MSE) and the 95% confidence intervals (95% CI) to externally evaluate the model.

RESULTS

The population values of pharmacokinetic parameters estimated in the final model were as follows: Ka=0.83 h-1, Vd=0.67 L/kg, and CL=0.035 L·kg(-1)·h(-1). The enzyme-inducing AEDs (carbamazepine, phenytoin, phenobarbital) and newer generation AEDs (levetiracetam, lamotrigine, topiramate) increased the weight-normalized CL value of MHD by 17.4% and 10.5%, respectively, whereas the enzyme-inhibiting AED valproic acid decreased it by 3%. No significant association was found between the CL value of MHD and the other covariates. For the final model, the evaluation results (95% CI) were MPE=0.01 (-0.07-0.10) mg/L, MAE=0.46 (0.40-0.51) mg/L, MSE=0.39 (0.27-0.51) (mg/L)(2).

CONCLUSION

A PPK model of OXC in Chinese pediatric patients with epilepsy is established. The enzyme-inducing AEDs and some newer generation AEDs (lamotrigine, topiramate) could slightly increase the metabolism of MHD.

Effect of oral contraceptives on lamotrigine levels depends on comedication

OBJECTIVES

To evaluate prospectively the influence of cyclic oral contraceptive (OC) use on lamotrigine (LTG) serum levels when used in combination therapy.

METHODS

Women with epilepsy using LTG in combination with valproate (VPA; n=7), carbamazepine (CBZ; n=3) or oxcarbazepine (OXC; n=1) were evaluated during two periods of 28 days cyclic OC use, monitoring antiepileptic drug (AED) levels every other day with the dried blood spot sampling method. Results were compared with women on LTG monotherapy and OCs (n=12). Pharmacokinetic analysis was performed using NONMEM software.

RESULTS

Mean study population value of LTG clearance estimated by the final model was 3.17 l/h. Introduction of covariates for comedication (VPA, CBZ, OXC and OC) significantly reduced the between-subject variability. A significant influence of OC comedication on LTG clearance was seen in both LTG monotherapy (clearance with OC 4.02±0.38 l/h, OC-free week 3.03±0.39 l/h) and in LTG-CBZ combination (clearance with OC 4.95±0.15 l/h, OC-free week 4.15±0.26 l/h). No influence of OC was found in LTG-VPA combination (clearance with OC 0.99±0.16 l/h, OC-free week 0.90±0.15 l/h).

CONCLUSIONS

Adding OCs to LTG monotherapy or the combination LTG-CBZ significantly increased the LTG clearance and thus reduced LTG serum levels. In the combination LTG-CBZ, OCs had a non-significant effect on CBZ clearance. No significant influence of cyclic OC use on LTG or VPA clearance was found when these AEDs were used in combination.

Pain and temporomandibular disorders: a pharmaco-gender dilemma

Gender is the biggest risk factor in the development of temporomandibular disorders (TMD) and orofacial pain. Gender differences in pain thresholds, temporal summation, pain expectations, and somatic awareness exist in patients with chronic TMD or orofacial pain. There are gender differences in pharmacokenetics and pharmacodynamics of medications used to treat pain. A better understanding of the mechanisms that contribute to the increased incidence and persistence of chronic pain in females is needed. Future research will elucidate the sex effects on factors that protect against developing pain or prevent debilitating pain. Gender-based treatments for TMD and orofacial pain treatment will evolve from the translational research stimulated by this knowledge.

Therapeutic drug monitoring of antiepileptic drugs by use of saliva

Blood (serum/plasma) antiepileptic drug (AED) therapeutic drug monitoring (TDM) has proven to be an invaluable surrogate marker for individualizing and optimizing the drug management of patients with epilepsy. Since 1989, there has been an exponential increase in AEDs with 23 currently licensed for clinical use, and recently, there has been renewed and extensive interest in the use of saliva as an alternative matrix for AED TDM. The advantages of saliva include the fact that for many AEDs it reflects the free (pharmacologically active) concentration in serum; it is readily sampled, can be sampled repetitively, and sampling is noninvasive; does not require the expertise of a phlebotomist; and is preferred by many patients, particularly children and the elderly. For each AED, this review summarizes the key pharmacokinetic characteristics relevant to the practice of TDM, discusses the use of other biological matrices with particular emphasis on saliva and the evidence that saliva concentration reflects those in serum. Also discussed are the indications for salivary AED TDM, the key factors to consider when saliva sampling is to be undertaken, and finally, a practical protocol is described so as to enable AED TDM to be applied optimally and effectively in the clinical setting. Overall, there is compelling evidence that salivary TDM can be usefully applied so as to optimize the treatment of epilepsy with carbamazepine, clobazam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, primidone, topiramate, and zonisamide. Salivary TDM of valproic acid is probably not helpful, whereas for clonazepam, eslicarbazepine acetate, felbamate, pregabalin, retigabine, rufinamide, stiripentol, tiagabine, and vigabatrin, the data are sparse or nonexistent.

Therapeutic drug monitoring in pregnancy

Therapeutic drug monitoring (TDM) is commonly recommended to optimize drug dosing regimens of various medications. It has been proposed to guide therapy in pregnant women, in whom physiological changes may lead to altered pharmacokinetics resulting in difficulty in predicting the appropriate drug dosage. Ideally, TDM may play a role in enhancing the effectiveness of treatment while minimizing toxicity of both the mother and fetus. Monitoring of drug levels may also be helpful in assessing adherence to prescribed therapy in selected cases. Limitations exist as therapeutic ranges have only been defined for a limited number of drugs and are based on data obtained in nonpregnant patients. TDM has been suggested for anticonvulsants, antidepressants, and antiretroviral drugs, based on pharmacokinetic studies that have shown reduced drug concentrations. However, there is only relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Further studies are required to determine whether implementation of TDM during pregnancy improves outcome and is associated with any benefit beyond that achieved by clinical judgment alone. The cost effectiveness of TDM programs during pregnancy also remains to be examined.

Second-generation antiepileptic drugs and pregnancy: a guide for clinicians

When treating pregnant women with antiepileptic drugs (AEDs), clinicians have to balance potential fetal adverse effects against the risks of uncontrolled maternal disease. Only recently have emerging scientic data provided a rational basis for treatment decisions considering both aspects. The focus of research is currently moving from the first to the second AED generation. Lamotrigine is relatively well studied, and data on other novel AEDs, such as levetiracetam, oxcarbazepine, topiramate, zonisamide, gabapentin and pregabalin, are in progress. Safety issues appear to be favorable for lamotrigine, and preliminary results are also promising for levetiracetam and oxcarbazepine. Drugs metabolized by uridine-diphospate glucuronosyl transferase or excreted unchanged by the kidneys are particularly susceptible to increased body clearance during pregnancy. Lamotrigine is subject to both mechanisms, and therapeutic serum levels may sometimes be difficult to maintain. The authors review the recommendations and clinical research on modern AED treatment during pregnancy, highlighting current experience with second-generation drugs.

What is next for dried blood spots?

In the last several years, dried blood spot (DBS) sampling has re-emerged and attracted a great interest in the pharmaceutical industry as a microsampling technology for drug discovery and development studies. Although significant progress has been made to understand strengths and weaknesses of the technique, many organizations are still at the evaluation stage and experimental observations have resulted in more questions being raised as to whether there is a real future for this technology in pharmaceutical research, especially in support of pharmacokinetic studies. This article summarizes recently gained knowledge against the originally projected advantages of this technique, discusses some practical challenges that need to be overcome before DBS can be widely applied in drug development studies, and highlights some specific study types where DBS can be applied with a good benefit:risk ratio. The authors hope this article can stimulate further discussions about what are the next steps for DBS.