Plasma vitamin values and antiepileptic therapy: case reports of pregnancy outcomes affected by a neural tube defect

Transporters in drug development: International transporter consortium update on emerging transporters of clinical importance

During its 4^th transporter workshop in 2021, the International Transporter Consortium (ITC) provided updates on emerging clinically relevant transporters for drug development. Previously highlighted and new transporters were considered based on up-to-date clinical evidence of their importance in drug-drug interactions and potential for altered drug efficacy and safety, including drug-nutrient interactions leading to nutrient deficiencies. For the first time, folate transport pathways (PCFT, RFC, and FRα) were examined in-depth as a potential mechanism of drug-induced folate deficiency and related toxicities (e.g., neural tube defects, megaloblastic anemia). However, routine toxicology studies conducted in support of drug development appear sufficient to flag such folate deficiency toxicities, while prospective prediction from in vitro folate metabolism and transport inhibition is not well enough established to inform drug development. Previous suggestion of retrospective study of intestinal OATP2B1 inhibition to explain unexpected decreases in drug exposure were updated. Furthermore, when the absorption of a new molecular entity is more rapid and extensive than can be explained by passive permeability, evaluation of OATP2B1 transport may be considered. Emerging research on hepatic and renal OAT2 is summarized, but current understanding of the importance of OAT2 was deemed insufficient to justify specific consideration for drug development. Hepatic, renal, and intestinal MRPs (MRP2, MRP3, MRP4) were revisited. MRPs may be considered when they are suspected to be the major determinant of drug disposition (e.g., direct glucuronide conjugates); MRP2 inhibition as a mechanistic explanation for drug-induced hyperbilirubinemia remains justified. There were no major changes in recommendations from previous ITC whitepapers.

Clinical Extrapolation of the Effects of Dolutegravir and Other HIV Integrase Inhibitors on Folate Transport Pathways

Preliminary analysis of ongoing birth surveillance study identified evidence of potential increased risk for neural tube defects (NTDs) in newborns associated with exposure to dolutegravir at the time of conception. Folate deficiency is a common cause of NTDs. Dolutegravir and other HIV integrase inhibitor drugs were evaluated in vitro for inhibition of folate transport pathways: proton-coupled folate transporter (PCFT), reduced folate carrier (RFC), and folate receptor α (FRα)-mediated endocytosis. Inhibition of folate transport was extrapolated to the clinic by using established approaches for transporters in intestine, distribution tissues, and basolateral and apical membranes of renal proximal tubules (2017 FDA Guidance). The positive controls, methotrexate and pemetrexed, demonstrated clinically relevant inhibition of PCFT, RFC, and FRα in folate absorption, distribution, and renal sparing. Valproic acid was used as a negative control that elicits folate-independent NTDs; valproic acid did not inhibit PCFT, RFC, or FRα At clinical doses and exposures, the observed in vitro inhibition of FRα by dolutegravir and cabotegravir was not flagged as clinically relevant; PCFT and RFC inhibition was not observed in vitro. Bictegravir inhibited both PCFT and FRα, but the observed inhibition did not reach the criteria for clinical relevance. Elvitegravir and raltegravir inhibited PCFT, but only raltegravir inhibition of intestinal PCFT was flagged as potentially clinically relevant at the highest 1.2-g dose (not the 400-mg dose). These studies showed that dolutegravir is not a clinical inhibitor of folate transport pathways, and it is not predicted to elicit clinical decreases in maternal and fetal folate levels. Clinically relevant HIV integrase inhibitor drug class effect on folate transport pathways was not observed. SIGNIFICANCE STATEMENT: Preliminary analysis of ongoing birth surveillance study identified evidence of potential increased risk for neural tube defects (NTDs) in newborns associated with exposure to the HIV integrase inhibitor dolutegravir at the time of conception; folate deficiency is a common cause of NTDs. Dolutegravir and other HIV integrase inhibitor drugs were evaluated in vitro for inhibition of the major folate transport pathways: proton-coupled folate transporter, reduced folate carrier, and folate receptor α-mediated endocytosis. The present studies showed that dolutegravir is not a clinical inhibitor of folate transport pathways, and it is not predicted to elicit clinical decreases in maternal and fetal folate levels. Furthermore, clinically relevant HIV integrase inhibitor drug class effect on folate transport pathways was not observed.

WITHDRAWN: Preconception counselling for women with epilepsy to reduce adverse pregnancy outcome

This review has been replaced by the protocol 'Preconception counselling for women with epilepsy' (Winterbottom 2014). The full review is expected to be published by 1st July 2014.

The editorial group responsible for this previously published document have withdrawn it from publication.

Homocysteine, folate, vitamin B12 and B6 in mothers of children with neural tube defects in Xinjiang, China

AIM

To investigate the maternal homocysteine (Hcy), folate, vitamin B(12) and B(6) , and their relations to neural tube defects (NTDs).

METHODS

Thirty mothers of NTDs offspring and another 60 mothers of normal children were enrolled as the patient and control groups from Xinjiang, China, from January 2008 to May 2011. The plasma levels of Hcy, folate, vitamin B(12) and B(6) were measured and compared between the two groups.

RESULTS

The morbidity of NTDs was 2.44% in Xinjiang. The Hcy was significantly higher in patient group than in control group (15.1 ± 7.8 vs. 8.5 ± 4.0 μmol/L, p < 0.001). The folate in patient group (9.7 ± 8.1 μg/L) was lower than in control group (15.0 ± 8.1 μg/L, p < 0.001). The vitamin B(12) was 181.3 ± 107.7 and 394.3 ± 386.3 ng/L in patient and control groups, respectively, with a significant difference (p < 0.001). The abnormal frequency of Hcy and vitamin B(12) was statistically different in two groups. The difference of vitamin B(6) between the patients and controls was marginal (48.7 ± 16.5 vs. 42.0 ± 10.5 mg/L, p = 0.051). Moreover, folate and vitamin B(12) levels were negatively correlated with Hcy while vitamin B(6) was positively correlated with Hcy. Positive correlation was observed between folate and vitamin B(12) levels.

CONCLUSION

Our data confirm that higher Hcy, lower folate and vitamin B(12) are risk factors for NTDs. Besides folate, vitamin B(12) should be supplied to decrease NTDs occurrence. Further study is required to investigate the levels and accurate role of vitamin B(6).

Antiepileptic drugs and pregnancy outcomes

The treatment of epilepsy in women of reproductive age remains a clinical challenge. While most women with epilepsy (WWE) require anticonvulsant drugs for adequate control of their seizures, the teratogenicity associated with some antiepileptic drugs (AEDs) is a risk that needs to be carefully addressed. Antiepileptic medications are also used to treat an ever broadening range of medical conditions such as bipolar disorder, migraine prophylaxis, cancer, and neuropathic pain. Despite the fact that the majority of pregnancies of WWE who are receiving pharmacological treatment are normal, studies have demonstrated that the risk of having a pregnancy complicated by a major congenital malformation is doubled when comparing the risk of untreated pregnancies. Furthermore, when AEDs are used in polytherapy regimens, the risk is tripled, especially when valproic acid (VPA) is included. However, it should be noted that the risks are specific for each anticonvulsant drug. Some investigations have suggested that the risk of teratogenicity is increased in a dose-dependent manner. More recent studies have reported that in utero exposure to AEDs can have detrimental effects on the cognitive functions and language skills in later stages of life. In fact, the FDA just issued a safety announcement on the impact of VPA on cognition (Safety Announcement 6-30-2011). The purpose of this document is to review the most commonly used compounds in the treatment of WWE, and to provide information on the latest experimental and human epidemiological studies of the effects of AEDs in the exposed embryos.

Does folic acid use decrease the risk for spina bifida after in utero exposure to valproic acid?

PURPOSE

Women with child wish are advised to take folic acid supplements to reduce the risk for spina bifida. However, there is less evidence for this protective effect in women using valproic acid (VPA). We investigated the effect of folic acid in women exposed to VPA in the first trimester of pregnancy.

METHODS

A case-control study was performed with data from a population-based registry of congenital malformations. Our cases were spina bifida registrations and all other malformed registrations (excluding folic acid sensitive malformations) were used as controls.

RESULTS

The ORs for the effect of correct folic acid use were calculated among antiepileptic drug (AED) unexposed pregnancies 0.5 [95%CI: 0.3-0.7] and among VPA exposed pregnancies 1.0 [95%CI: 0.1-7.6].

DISCUSSION

Due to power-reasons, we cannot conclude that folic acid has no effect on the risk for spina bifida among VPA exposed pregnancies. Although for AED unexposed pregnancies we found a decreased risk. Results from (animal) studies support a biologically plausible association between VPA, folic acid and spina bifida. While folic acid might not be able to reduce the risk for lower spina bifida lesions caused by VPA, the use of folic acid might be important to reduce the risk for higher, folic acid sensitive spina bifida lesions. Further research is needed to get more insight in the most effective form and dose of FA in women that use VPA to reduce the risk for (higher forms of) spina bifida.

Teratogenic effects of antiepileptic drugs

Many antiepileptic drugs (AEDs) have therapeutic applications that extend beyond epilepsy to include neuropathic pain, migraine headaches and psychiatric disorders. The risk of some AEDs has been clearly established, but for newer drugs, small sample sizes and polytherapy exposures preclude a conclusive determination of their teratogenic potential. Most women with epilepsy will require AED therapy throughout their entire pregnancy to control seizures; the vast majority of pregnancies in women with epilepsy have positive outcomes. A conservative estimate suggests that AED monotherapy doubles, and polytherapy triples, the risk for major congenital malformations. Furthermore, while evidence is still accruing, recent investigations suggest that exposure to select AEDs results in altered cognitive function later in development. There is no evidence to suggest that additional folic acid supplementation ameliorates the increased risk of congenital malformations conferred by in utero AED exposure.

The effectiveness of preconception counseling to reduce adverse pregnancy outcome in women with epilepsy: what's the evidence?

OBJECTIVE

The purpose of this Cochrane review was to determine the effectiveness of delivering preconception counseling interventions to women with epilepsy (WWE) as a means of reducing adverse pregnancy outcomes, increasing knowledge, and increasing intentions to plan pregnancy.

METHODS

Two hundred twenty-five citations were retrieved from a systematic search of the Cochrane Library and electronic databases: Medline (OVID), Scopus, CINAHL, PsychINFO, and ASSIA, and hand searches of relevant epilepsy and obstetric journals.

RESULTS

The search strategy identified 11 studies for consideration for inclusion. However, none met the required criteria for inclusion.

CONCLUSIONS

There is no robust evidence to inform the content, methods of delivery, or likely effectiveness of preconception counseling to improve pregnancy outcomes for WWE and their offspring. The value of counseling WWE prior to conception remains uncertain and requires evaluation in well-designed studies, appropriately powered to detect changes likely associated with both maternal and infant outcomes.

Preconception counselling for women with epilepsy to reduce adverse pregnancy outcome

BACKGROUND

The provision of preconception counselling to women with epilepsy (WWE) has become established as recommended practice and includes a review of drug treatment and the provision of information and advice on both seizure and treatment-related risks to both mother and child. In this review we assess the evidence regarding the effectiveness of preconception counselling for WWE.

OBJECTIVES

To determine the effectiveness of preconception counselling for WWE, measured by a reduction in adverse pregnancy outcome in both mother and child; increased knowledge of preconception issues in WWE and increasing intention to plan pregnancy.

SEARCH STRATEGY

We searched the Epilepsy Group's Specialized Register (30/01/2008), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2007, Issue 4), and electronic databases: MEDLINE (OVID) (1950-February 2008); SCOPUS (1966-March 2008); CINAHL (1982-March 2008); PsyclNFO (1806-March 2008); ASSIA (1987-March 2008).

SELECTION CRITERIA

Randomised control trials; including cluster and quasi-randomised trials, prospective cohorts, controlled before and after studies, and interrupted time series that compared the outcomes in mothers with epilepsy and infants of mothers with epilepsy who received preconception counselling, to the outcomes of mothers with epilepsy and their infants who received standard care or no intervention.

DATA COLLECTION AND ANALYSIS

The methodological quality of potentially relevant studies were assessed to determine appropriate inclusion. Where necessary, study authors were contacted for additional information. No studies met the review inclusion criteria.

MAIN RESULTS

The search strategy identified 11 studies for consideration of inclusion. However, none met the required criteria for inclusion.

AUTHORS' CONCLUSIONS

There is no evidence to inform the content, methods of delivery or effectiveness of preconception counselling to improve pregnancy outcomes for WWE and their offspring. The value of counselling delivered to WWE prior to conception, with the intention of reducing the risks of adverse outcome in mother and child, requires evaluation in well-designed studies, appropriately powered to detect changes in both maternal and infant outcome.