Pharmacokinetics of Sulfadoxine and Pyrimethamine for Intermittent Preventive Treatment of Malaria During Pregnancy and After Delivery

Determination of sulfadoxine and pyrimethamine in microvolume human plasma using ultra high performance liquid chromatography-tandam mass spectrometry

To support the pharmacokinetic study of sulfadoxine (SD) and pyrimethamine (PM) in pregnant women and children, sensitive methods with small sample volume are desirable. Here we report a method to determine SD and PM with microvolume plasma samples: 5 µL plasma samples were cleaned up by protein precipitation with acetonitrile. The deuterated analytes were used as the internal standards. The samples after cleanup were injected onto an ACE Excel SuperC18 column (50 × 2.1 mm, 1.7 μm, Hichrom Limited) connected to a Waters I class UPLC coupled with a Sciex Triple Quad 6500+ Mass Spectrometer and eluted with water and acetonitrile both containing 0.1% formic acid in a gradient mode at 0.8mL/min. Detection utilized ESI+ as the ion source and MRM as the quantification mode. The precursor-to-product ion transitions m/z 311→245 for SD and 249→233 for PM were selected for quantification. The ion transitions for the corresponding internal standards were 315→249 for SD-d4 and 254→235 for PM-d3. The simplest linear regression weighted by 1/x was used for the calibration curves. The calibration ranges were 1-200 µg/mL SD and 2 - 1000ng/mL PM. The mean (± standard deviation) recoveries were 94.3±3.2% (SD) and 97.0±1.5% (PM). The validated method was applied to analysis of 1719 clinical samples, demonstrating the method is suitable for the pharmacokinetic study with samples collected up to day 28 post-dose.

Optimizing Therapeutic Drug Monitoring in Pregnant Women: A Critical Literature Review

BACKGROUND

More than 90% of pregnant women take at least one drug during pregnancy. Drug dose adjustments during pregnancy are sometimes necessary due to various pregnancy-induced physiological alterations frequently associated with lower plasma concentrations. However, the clinical relevance or benefits of therapeutic drug monitoring (TDM) in pregnant women have not been specifically studied. Clinical pharmacokinetic studies in pregnant women are incredibly challenging for many reasons. Despite this, regulatory agencies have made efforts to encourage the inclusion of this population in clinical trials to achieve more information on the pharmacotherapy of pregnant women. This review aims to provide support for TDM recommendations and dose adjustments in pregnant women.

METHODS

The search was conducted after a predetermined strategy on PubMed and Scopus databases using the MeSH term "pregnancy" alongside other terms such as "Pregnancy and dose adjustment," "Pregnancy and therapeutic drug monitoring," "Pregnancy and PBPK," "Pregnancy and pharmacokinetics," and "Pregnancy and physiological changes."

RESULTS

The main information on TDM in pregnant women is available for antiepileptics, antipsychotics, antidepressants, antibiotics, antimalarials, and oncologic and immunosuppressive drugs.

CONCLUSIONS

More data are needed to support informed benefit-risk decision making for the administration of drugs to pregnant women. TDM and/or pharmacokinetic studies could ensure that pregnant women receive an adequate dosage of an active drug. Mechanistic modeling approaches potentially could increase our knowledge about the pharmacotherapy of this special population, and they could be used to better design dosage regimens.

Evaluation of the usefulness of intermittent preventive treatment of malaria in pregnancy with sulfadoxine-pyrimethamine in a context with increased resistance of Plasmodium falciparum in Kingasani Hospital, Kinshasa in the Democratic Republic of Congo

BACKGROUND

Increasing resistance of Plasmodium falciparum to sulfadoxine-pyrimethamine (SP) threatens its usefulness for intermittent preventive treatment in pregnancy (IPTp-SP). The prophylactic effects of IPTp-SP on maternal malaria and adverse pregnancy outcomes were evaluated in Kingasani Hospital, Kinshasa in the Democratic Republic of Congo (DRC).

METHODS

Laboring women (n = 844) and respective newborns were investigated. Blood samples collected from women were tested for malaria using rapid diagnostic test (RDT), blood smears examination, and real-time PCR. The hemoglobin level was measured by HemoCue© analyzer. A PCR-RFLP method was applied for detecting N51I, C59R, and S108N mutations on dhfr along with A437G and K540E mutations on dhps in P. falciparum positive samples. Logistic regression models assessed relationships between IPTp-SP uptake and pregnancy outcomes.

RESULTS

P. falciparum malaria was detected at delivery in 10.8% of women and was statistically associated with fever during the pregnancy (OR = 2.9 [1.5; 6.3]; p = 0.004) and maternal anemia (OR = 3.9 [2.4; 6.3]; p < 0.001). One out of five parasites was a quintuple mutant encoding dhfr mutations 51I, 59R, and 108 N along with dhps mutations 437G and 540E. The molecular profile of parasites (i.e., 32.6% of parasites carrying dhps K540E) was suitable with continued use of SP for IPTp. IPTp-SP uptake was not associated with reduced maternal malaria, fever reported in pregnancy, or fetal deaths (p > 0.05). Conversely, three or more doses of SP were associated with reduced maternal anemia at delivery (OR = 0.4 [0.2; 0.9]; p = 0.024), shortened gestation (OR = 0.4 [0.2; 0.8]; p = 0.009), and low-birth weights (OR = 0.2 [0.1; 0.5]; p < 0.001).

CONCLUSION

IPTp-SP was not associated with reduced maternal malaria in our study, but evidence was found of a prophylactic effect against adverse pregnancy outcomes. To counteract further loss of clinical effects of IPTp-SP in the study population, alternative strategies able to improve its anti-malarial efficacy such as combination of SP with partner molecules should be implemented.

Fansidar drug induces cytotoxicity in some vital tissues in a rat model: combination defensive effect of selenium and zinc capsules

AIM

Fansidar (FAN) is widely used as an antimalarial drug, but it may cause hepatoxicity, nephrotoxicity, and neurotoxicity. Hence, the study examines the cytoprotection of selenium (Se) and zinc (Zn) tablets against FAN induced toxicity.

METHOD

Group I was given distilled water. Groups II, III, IV, and V received 50 mg/kg FAN by gavage. Group III was co-treated with a 50 mg/kg Se tablet. Group IV was co-treated with a 50 mg/kg Zn tablet. Group V was co-treated with a 50 mg/kg Se tablet + 50 mg/kg Zn tablet. The exposure lasted for 7 days (sub-acute exposure).

RESULT

FAN causes cytotoxicity through significant (p < 0.05) alteration of antioxidant molecules and hepatic enzymes. It also significantly (p < 0.05) induces renal, hepatocyte, and purkinje cell damage, but no visible lesion on testicular cells. The FAN induced cytotoxicity was significantly (p < 0.05) reversed on treatment with both single and combined antioxidant tablets.

CONCLUSION

Our study supports the view that antioxidant micronutrient (Se and Zn) tablets may be a useful modulator in alleviating FAN induced oxidative stress and cytotoxicity in male rats.

PLAIN LANGUAGE SUMMARY

Combined selenium and zinc capsules: better therapy against cytotoxicity Fansidar was approved by United States' Food and Drug Administration as an anti-malarial drug to treat acute and complicated malaria fever among patients in West Africa; however, its usage elicits toxicity to several organs of the body. It was elucidated that the combination of selenium and zinc capsules promotes organ wellness on co-treatment with Fansidar.

Sulfadiazine plasma concentrations in women with pregnancy-acquired compared to ocular toxoplasmosis under pyrimethamine and sulfadiazine therapy: a case-control study

Background

Dosing recommendations for the treatment of pregnancy-acquired toxoplasmosis are empirical and widely based on experimental data. There are no pharmacological data on pregnant women with acute Toxoplasma gondii infection under treatment with pyrimethamine (PY) and sulfadiazine (SA) and our study intends to tighten this gap.

Methods

In this retrospective case–control study, we included 89 pregnant women with primary Toxoplasma infection (PT) treated with PY (50 mg first dose, then 25 mg/day), SA (50 mg/kg of body weight/day), and folinic acid (10–15 mg per week). These were compared to a group of 17 women with acute ocular toxoplasmosis (OT) treated with an initial PY dose of 75 mg, thereafter 25 mg twice a day but on the same SA and folinic acid regimen. The exact interval between drug intake and blood sampling and co-medication had not been recorded. Plasma levels of PY and SA were determined 14 ± 4 days after treatment initiation using liquid chromatography–mass spectrometry and compared using the Mann–Whitney U test at a p < 0.05 level.

Results

In 23 PT patients (26%), SA levels were below 20 mg/l. Fifteen of these 23 patients (17% of all patients) in parallel presented with PY levels below 700 µg/l. Both drug concentrations differed remarkably between individuals and groups (PY: PT median 810 µg/l, 95% CI for the median [745; 917] vs. OT 1230 µg/l [780; 1890], p = 0.006; SA: PT 46.2 mg/l [39.9; 54.4] vs. OT 70.4 mg/l [52.4; 89], p = 0.015) despite an identical SA dosing scheme.

Conclusions

SA plasma concentrations were found in the median 34% lower in pregnant women with PT compared to OT patients and fell below a lower reference value of 50 mg/l in a substantial portion of PT patients. The interindividual variability of plasma concentrations in combination with systematically lower drug levels and possibly a lower compliance in pregnant women may thus account for a still not yet supportable transmission risk. Systematic drug-level testing in PT under PY/SA treatment deserves to be considered.

Deleterious effects of malaria in pregnancy on the developing fetus: a review on prevention and treatment with antimalarial drugs

All malaria infections are harmful to both the pregnant mother and the developing fetus. One in ten maternal deaths in malaria endemic countries are estimated to result from Plasmodium falciparum infection. Malaria is associated with a 3-4 times increased risk of miscarriage and a substantially increased risk of stillbirth. Current treatment and prevention strategies reduce, but do not eliminate, malaria's damaging effects on pregnancy outcomes. Reviewing evidence generated from meta-analyses, systematic reviews, and observational data, the first paper in this Series aims to summarise the adverse effects of malaria in pregnancy on the fetus and how the current drug treatment and prevention strategies can alleviate these effects. Although evidence supports the safety and treatment efficacy of artemisinin-based combination therapies in the first trimester, these therapies have not been recommended by WHO for the treatment of malaria at this stage of pregnancy. Intermittent preventive treatment of malaria in pregnancy with sulfadoxine-pyrimethamine is contraindicated in the first trimester and provides imperfect chemoprevention because of inadequate dosing, poor (few and late) antenatal clinic attendance, increasing antimalarial drug resistance, and decreasing naturally acquired maternal immunity due to the decreased incidence of malaria. Alternative strategies to prevent malaria in pregnancy are needed. The prevention of all malaria infections by providing sustained exposure to effective concentrations of antimalarial drugs is key to reducing the adverse effects of malaria in pregnancy.

Prioritization of Anti-SARS-Cov-2 Drug Repurposing Opportunities Based on Plasma and Target Site Concentrations Derived from their Established Human Pharmacokinetics

There is a rapidly expanding literature on the in vitro antiviral activity of drugs that may be repurposed for therapy or chemoprophylaxis against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2). However, this has not been accompanied by a comprehensive evaluation of the target plasma and lung concentrations of these drugs following approved dosing in humans. Accordingly, concentration 90% (EC90 ) values recalculated from in vitro anti-SARS-CoV-2 activity data was expressed as a ratio to the achievable maximum plasma concentration (Cmax ) at an approved dose in humans (Cmax /EC90 ratio). Only 14 of the 56 analyzed drugs achieved a Cmax /EC90 ratio above 1. A more in-depth assessment demonstrated that only nitazoxanide, nelfinavir, tipranavir (ritonavir-boosted), and sulfadoxine achieved plasma concentrations above their reported anti-SARS-CoV-2 activity across their entire approved dosing interval. An unbound lung to plasma tissue partition coefficient (Kp Ulung ) was also simulated to derive a lung Cmax /half-maximal effective concentration (EC50 ) as a better indicator of potential human efficacy. Hydroxychloroquine, chloroquine, mefloquine, atazanavir (ritonavir-boosted), tipranavir (ritonavir-boosted), ivermectin, azithromycin, and lopinavir (ritonavir-boosted) were all predicted to achieve lung concentrations over 10-fold higher than their reported EC50 . Nitazoxanide and sulfadoxine also exceeded their reported EC50 by 7.8-fold and 1.5-fold in lung, respectively. This analysis may be used to select potential candidates for further clinical testing, while deprioritizing compounds unlikely to attain target concentrations for antiviral activity. Future studies should focus on EC90 values and discuss findings in the context of achievable exposures in humans, especially within target compartments, such as the lungs, in order to maximize the potential for success of proposed human clinical trials.

Updated pharmacokinetic considerations for the use of antimalarial drugs in pregnant women

INTRODUCTION

The association between pregnancy and altered drug pharmacokinetic (PK) properties is acknowledged, as is its impact on drug plasma concentrations and thus therapeutic efficacy. However, there have been few robust PK studies of antimalarial use in pregnancy. Given that inadequate dosing for prevention or treatment of malaria in pregnancy can result in negative maternal/infant outcomes, along with the potential to select for parasite drug resistance, it is imperative that reliable pregnancy-specific dosing recommendations are established.

AREAS COVERED

PK studies of antimalarial drugs in pregnancy. The present review summarizes the efficacy and PK properties of WHO-recommended therapies used in pregnancy, with a focus on PK studies published since 2014.

EXPERT OPINION

Changes in antimalarial drug disposition in pregnancy are well described, yet pregnant women continue to receive treatment regimens optimized for non-pregnant adults. Contemporary in silico modeling has recently identified a series of alternative dosing regimens that are predicted to provide optimal therapeutic efficacy for pregnant women.

Effect of sulfadoxine-pyrimethamine doses for prevention of malaria during pregnancy in hypoendemic area in Tanzania

BACKGROUND

Malaria in pregnancy increases the risk of deleterious maternal and birth outcomes. The use of ≥ 3 doses of sulfadoxine-pyrimethamine (SP) for intermittent preventive treatment of malaria (IPTp-SP) is recommended for preventing the consequences of malaria during pregnancy. This study assessed the effect of IPTp-SP for prevention of malaria during pregnancy in low transmission settings.

METHODS

A cross-sectional study that involved consecutively selected 1161 pregnant women was conducted at Mwananyamala regional referral hospital in Dar es Salaam. Assessment of the uptake of IPTp-SP was done by extracting information from antenatal clinic cards. Maternal venous blood, cord blood, placental blood and placental biopsy were collected for assessment of anaemia and malaria. High performance liquid chromatography with ultraviolet detection (HPLC-UV) was used to detect and quantify sulfadoxine (SDX). Dried blood spots (DBS) of placental blood were collected for determination of sub-microscopic malaria using polymerase chain reaction (PCR).

RESULTS

In total, 397 (34.2%) pregnant women reported to have used sub-optimal doses (≤ 2) while 764 (65.8%) used optimal doses (≥ 3) of IPTp-SP at the time of delivery. The prevalence of placental malaria as determined by histology was 3.6%. Submicroscopic placental malaria was detected in 1.4% of the study participants. Women with peripheral malaria had six times risk of maternal anaemia than those who were malaria negative (aOR, 5.83; 95% CI 1.10-30.92; p = 0.04). The geometric mean plasma SDX concentration was 10.76 ± 2.51 μg/mL. Sub-optimal IPTp-SP dose was not associated with placental malaria, premature delivery and fetal anaemia. The use of ≤ 2 doses of IPTp-SP increased the risk of maternal anaemia by 1.36-fold compared to ≥ 3 doses (aOR, 1.36; 95% CI 1.04-1.79; p = 0.02).

CONCLUSION

The use of < 2 doses of IPTp-SP increased the risk of maternal anaemia. However, sub-optimal doses (≤ 2 doses) were not associated with increased the risk of malaria parasitaemia, fetal anaemia and preterm delivery among pregnant women in low malaria transmission setting. The use of optimal doses (≥ 3 doses) of IPTp-SP and complementary interventions should continue even in areas with low malaria transmission.

Evaluation of the Pharmacokinetics, Safety, and Tolerability of a Single Oral Dose of Pyrimethamine in Healthy Male Subjects of Japanese and European Ancestry

The pharmacokinetics of pyrimethamine have been evaluated in various populations but have not been reported in subjects of Japanese ancestry following administration as a single-agent tablet. Furthermore, although pyrimethamine pharmacokinetics after a single dose of the single-agent tablet studied in Western countries have been reported, these studies are old, and the ancestry of the subjects was not specified. Consequently, this study investigated the pharmacokinetics and safety of a single oral 50-mg dose of pyrimethamine in healthy male subjects of Japanese and European ancestry. Seven subjects of each ancestry group were administered pyrimethamine, along with calcium folinate. After absorption, pyrimethamine was eliminated, with a mean half-life of 122.8 hours in Japanese subjects and 99.5 hours in European subjects. The mean C_max and AUC_0-t were 433.8 ng/mL and 59.63 µg·h/mL in Japanese subjects and 372.7 ng/mL and 42.83 µg·h/mL in European subjects. No safety concerns were reported during the study. Although pyrimethamine exposure was slightly higher in subjects of Japanese than of European ancestry, a considerable overlap in the range of parameter values was observed. Considering the range of pyrimethamine exposure reported previously, difference in exposure observed in this study would not be considered of note.

Modeling Prevention of Malaria and Selection of Drug Resistance with Different Dosing Schedules of Dihydroartemisinin-Piperaquine Preventive Therapy during Pregnancy in Uganda

Dihydroartemisinin-piperaquine (DHA-PQ) is under study for intermittent preventive treatment during pregnancy (IPTp), but it may accelerate selection for drug resistance. Understanding the relationships between piperaquine concentration, prevention of parasitemia, and selection for decreased drug sensitivity can inform control policies and optimization of DHA-PQ dosing. Piperaquine concentrations, measures of parasitemia, and Plasmodium falciparum genotypes associated with decreased aminoquinoline sensitivity in Africa (pfmdr1 86Y, pfcrt 76T) were obtained from pregnant Ugandan women randomized to IPTp with sulfadoxine-pyrimethamine (SP) or DHA-PQ. Joint pharmacokinetic/pharmacodynamic models described relationships between piperaquine concentration and the probability of genotypes of interest using nonlinear mixed effects modeling. An increase in the piperaquine plasma concentration was associated with a log-linear decrease in risk of parasitemia. Our models predicted that higher median piperaquine concentrations would be required to provide 99% protection against mutant infections than against wild-type infections (pfmdr1: N86, 9.6 ng/ml; 86Y, 19.6 ng/ml; pfcrt: K76, 6.5 ng/ml; 76T, 19.6 ng/ml). Comparing monthly, weekly, and daily dosing, daily low-dose DHA-PQ was predicted to result in the fewest infections and the fewest mutant infections per 1,000 pregnancies (predicted mutant infections for pfmdr1 86Y: SP monthly, 607; DHA-PQ monthly, 198; DHA-PQ daily, 1; for pfcrt 76T: SP monthly, 1,564; DHA-PQ monthly, 283; DHA-PQ daily, 1). Our models predict that higher piperaquine concentrations are needed to prevent infections with the pfmdr1/pfcrt mutant compared to those with wild-type parasites and that, despite selection for mutants by DHA-PQ, the overall burden of mutant infections is lower for IPTp with DHA-PQ than for IPTp with SP. (This study has been registered at ClinicalTrials.gov under identifier NCT02282293.).

Antimalarial drugs for treating and preventing malaria in pregnant and lactating women

INTRODUCTION

Malaria in pregnancy and postpartum cause maternal mortality and adverse fetal outcomes. Efficacious and safe antimalarials are needed to treat and prevent such serious consequences. However, because of the lack of evidence on fetal safety, quinine, an old and less efficacious drug has long been recommended for pregnant women. Uncertainty about safety in relation to breastfeeding leads to withholding of efficacious treatments postpartum or cessation of breastfeeding. Areas covered: A search identified literature on humans in three databases (MEDLINE, Embase and Global health) using pregnancy or lactation, and the names of antimalarial drugs as search terms. Adverse reactions to the mother, fetus or breastfed infant were summarized together with efficacies. Expert opinion: Artemisinins are more efficacious and well-tolerated than quinine in pregnancy. Furthermore, the risks of miscarriage, stillbirth or congenital abnormality were not higher in pregnancies exposed to artemisinin derivatives for treatment of malaria than in pregnancies exposed to quinine or in the comparable background population unexposed to any antimalarials, and this was true for treatment in any trimester. Assessment of safety and efficacy of antimalarials including dose optimization for pregnant women is incomplete. Resistance to sulfadoxine-pyrimethamine in Plasmodium falciparum and long unprotected intervals between intermittent treatment doses begs reconsideration of current preventative recommendations in pregnancy. Data remain limited on antimalarials during breastfeeding; while most first-line drugs appear safe, further research is needed.

Pharmacotherapy for the prevention of malaria in pregnant women: currently available drugs and challenges

INTRODUCTION

Malaria in pregnancy continues to be a significant public health burden globally, with over 100 million women at risk each year. Sulfadoxine-pyrimethamine (SP) is the only antimalarial recommended for intermittent preventive therapy in pregnancy (IPTp) but increasing parasite resistance threatens its viability. There are few other available antimalarial therapies that currently have sufficient evidence of tolerability, safety, and efficacy to replace SP.

AREAS COVERED

Novel antimalarial combinations are under investigation for potential use as chemoprophylaxis and in IPTp regimens. The present review summarizes currently available therapies, emerging candidate combination therapies, and the potential challenges to integrating these into mainstream policy.

EXPERT OPINION

Alternative drugs or combination therapies to SP for IPTp are desperately required. Dihydroartemisinin-piperaquine and azithromycin-based combinations are showing great promise as potential candidates for IPTp but pharmacokinetic data suggest that dose modification may be required to ensure adequate prophylactic efficacy. If a suitable candidate regimen is not identified in the near future, the success of chemopreventive strategies such as IPTp may be in jeopardy.

Utilization of data below the analytical limit of quantitation in pharmacokinetic analysis and modeling: promoting interdisciplinary debate

Traditionally, bioanalytical laboratories do not report actual concentrations for samples with results below the LOQ (BLQ) in pharmacokinetic studies. BLQ values are outside the method calibration range established during validation and no data are available to support the reliability of these values. However, ignoring BLQ data can contribute to bias and imprecision in model-based pharmacokinetic analyses. From this perspective, routine use of BLQ data would be advantageous. We would like to initiate an interdisciplinary debate on this important topic by summarizing the current concepts and use of BLQ data by regulators, pharmacometricians and bioanalysts. Through introducing the limit of detection and evaluating its variability, BLQ data could be released and utilized appropriately for pharmacokinetic research.