Pharmacokinetics of Increased Nelfinavir Plasma Concentrations in Women During Pregnancy and Postpartum

This study aims to evaluate the safety, acceptability, and pharmacokinetics (PK) of an increased dose of nelfinavir (NFV) during the third trimester of pregnancy. The study was registered as part of the International Maternal Pediatric Adolescent AIDS Clinical Trials network (IMPAACT-P1026s), an ongoing multicenter prospective cohort study of antiretroviral PK during pregnancy (NCT00042289). NFV intensive PK evaluations were performed at steady state during the third trimester of pregnancy and 2-3 weeks postpartum. Plasma concentrations of NFV and its active metabolite, hydroxyl-tert-butylamide (M8) were measured using high-performance liquid chromatography with ultraviolet detection. A total of 18 women are included in the analysis. NFV area under the concentration-time curve (AUC) with the increased dose during the third trimester was nearly identical to the standard dose postpartum, with a geometric mean ratio for third trimester to postpartum AUC of 0.98 (90%CI 0.71-1.35). Despite the increased dose, M8 AUC was lower during the third trimester compared to postpartum (0.53, IQR [0.38-0.75]), as was the M8/NFV AUC ratio (0.51, IQR [0.42-0.63]). NFV AUC_0-12 was above target in 15 of 18 (83%) of participants during the third trimester compared to 14 of 16 (88%) postpartum. No major safety concerns were noted. Increasing the NFV dose to 1875 mg twice daily during the third trimester achieved similar concentrations postpartum compared to standard dosing (1250 mg twice daily). Increased NFV dose regimens may still have some benefit to human immunodeficiency virus (HIV)-positive pregnant women living in countries where novel protease inhibitors are currently unavailable or in individuals who are intolerant to ritonavir-boosted HIV medications.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

Pharmacokinetics of Rilpivirine in HIV-Infected Pregnant Women

BACKGROUND

Rilpivirine pharmacokinetics is defined by its absorption, distribution, metabolism, and excretion. Pregnancy can affect these factors by changes in cardiac output, protein binding, volume of distribution, and cytochrome P450 (CYP) 3A4 activity. Rilpivirine is metabolized by CYP3A4. The impact of pregnancy on rilpivirine pharmacokinetics is largely unknown.

METHODS

International Maternal Pediatric Adolescent AIDS Clinical Trials P1026s is a multicenter, nonblinded, prospective study evaluating antiretroviral pharmacokinetics in HIV-infected pregnant women that included a cohort receiving rilpivirine 25 mg once daily as part of their combination antiretrovirals for clinical care. Thirty-two women were enrolled in this study. Intensive pharmacokinetic sampling was performed at steady state during the second trimester, the third trimester, and postpartum. Maternal and umbilical cord blood samples were obtained at delivery. Plasma rilpivirine concentration was measured using liquid chromatography-mass spectrometry; lower limit of quantitation was 10 ng/mL.

RESULTS

Median (range) AUC0-24 were 1969 (867-4987, n = 15), 1669 (556-4312, n = 28), and 2387 (188-6736, n = 28) ng·h/mL in the second trimester, the third trimester, and postpartum, respectively (P < 0.05 for either trimester vs postpartum). Median (range) C24 were 63 (37-225, n = 17), 56 (<10-181, n = 30), and 81 (<10-299, n = 28) ng/mL (P < 0.05 for either trimester vs postpartum). High variability in pharmacokinetic parameters was observed between subjects. Median (range) cord blood/maternal concentration ratio was 0.55 (0.3-0.8, n = 21). Delivery HIV-1 RNA was ≤50 copies per milliliter in 70% and ≤400 copies per milliliter in 90% of women. Cmin were significantly lower at 15 visits with detectable HIV-1 RNA compared with 61 visits with undetectable HIV-1 RNA, 29 (<10-93) vs 63 (15-200) ng/mL (P = 0.0001). Cmin was below the protein binding-adjusted EC90 concentration (12.2 ng/mL) at 4 visits in 3 of 31 women (10%).

CONCLUSIONS

Rilpivirine exposure is lower during pregnancy compared with postpartum and highly variable. Ninety percent of women had minimum concentrations above the protein binding-adjusted EC90 for rilpivirine.

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.

Pharmacological considerations on the use of antiretrovirals in pregnancy

PURPOSE OF REVIEW

Treatment with combination antiretroviral therapy during pregnancy reduces the chance of mother to child transmission of HIV. Physiological changes during pregnancy can lead to lower exposure to antiretrovirals, possibly resulting in virological failure. For most antiretrovirals, data on exposure during pregnancy and transplacental passage are limited. This review summarizes the most recent information on pharmacokinetics (including transplacental passage), efficacy, as well as the safety of antiretrovirals during pregnancy.

RECENT FINDINGS

Intensive-sampling pharmacokinetic studies as well as observational studies using sparse sampling were performed to explore the exposure to antiretrovirals during pregnancy. Transplacental passage, efficacy (viral load at delivery and infection status of the newborn) and safety information were evaluated for several antiretrovirals.

SUMMARY

For most nucleoside/nucleotide reverse transcriptase inhibitors and protease inhibitors, recent research shows a decreased exposure during pregnancy. However, the advantage of a general dose increase during pregnancy still remains unclear. For newer compounds and efavirenz, limited or no data on pharmacokinetics during pregnancy or transplacentally are available, while the mechanisms of transplacental passage also remain unknown. For safety reasons, it will be important to monitor pregnancy outcomes in resource-limited settings during the implementation of the WHO guidelines (including the use of efavirenz during pregnancy).

How does HIV affect the reproductive choices of women of childbearing age?

The majority of women living with HIV are of childbearing age and many of these women wish to have a family. As a result of advances in the treatment and management of HIV, more reproductive opportunities are now available to this group. However, women living with HIV may still require education and guidance in a range of reproductive situations, including avoiding pregnancy, seeking fertility treatment or having a child. HIV physicians should be aware of recent data and guidance on these situations--including areas where more data are required--and consider them when deciding on appropriate management for their patients.