Objective
Given the lack of data regarding the use of oseltamivir (Tamiflu) during pregnancy, we aimed to evaluate the placental transfer of oseltamivir phosphate and its active metabolite oseltamivir carboxylate, using the perfused placental cotyledon model.
Study Design
Cotyledons were coperfused with oseltamivir phosphate and oseltamivir carboxylate using the maximal concentrations described with a 75 mg, twice-daily oral dose. Main transfer parameters such as fetal transfer rate (FTR) and clearance index (CI) were assessed.
Results
Five placentas were coperfused with oseltamivir phosphate and oseltamivir carboxylate. The median FTR of oseltamivir phosphate was 8.5% (range, 5.0–11.6%) and the median CI was 0.3 (range, 0.2–0.6). Regarding oseltamivir carboxylate transplacental transfer, the median FTR was 6.6% (range, 3.9–9.7%), whereas the median CI was 0.2 (range, 0.2–0.5).
Conclusion
A transplacental transfer of oseltamivir phosphate and its metabolite oseltamivir carboxylate was detected and might have clinical relevance. Clinicians should be encouraged to report oseltamivir treatment outcomes during pregnancy.
Approximately 20% of the world’s population is annually affected by influenza, leading to 40,000 deaths in United States every year. In 2009, a novel strain of avian influenza virus (A/H1N1v) rapidly spread over to many countries in the world. Thus, in April 2009, the World Health Organization decided to raise the level of influenza pandemic alert from phase 4 to phase 5.
According to recent data from the Centers for Disease Control and Prevention, A/H1N1v seemed to be also sensitive to neuraminidase inhibitors antiviral agents such as oseltamivir or zanamivir during the active phase of disease. These drugs are recommended for all infected persons who are at increased risk for complications because they potentially reduce duration of symptoms, number of hospitalizations, and complications such as pneumonia and otitis. Moreover, antiviral therapies should be associated with annual influenza vaccination to be highly effective. Indeed, vaccination significantly reduces the occurrence of hospitalization and death in high-risk patients.
Oseltamivir phosphate (Tamiflu; F. Hoffmann-La Roche Ltd, Basel, Switzerland) is a prodrug, which is biotransformed into an active metabolite (oseltamivir carboxylate) by carboxylesterases. This active metabolite inhibits the activity of influenza type A and B neuraminidases (glycoproteins localized on the virions surface) and therefore interferes with the release of novel viral particles.
Among the high-risk group of patients, 2 categories of healthy persons also present an increased risk of complications: neonates (0-6 months) and pregnant women. Indeed, pregnancy is associated with a high risk of severe complications such as pneumoniae or acute respiratory distress syndrome. Given the risk of severe outcomes in pregnant patients, influenza vaccination is recommended in this population. Moreover, pregnant patients should also be treated with curative and prophylactic antiviral therapies. Recent data (mainly retrospective data and case series) recommended preferential use of oseltamivir rather than zanamivir because zanamivir-induced fetal toxicity has been less studied or described in pregnant patients.
However, given the paucity of data regarding the use of oseltamivir in pregnant patients, these recommendations leave questionable the fetal risk of the use of oseltamivir during pregnancy. Although most published data seem to be reassuring, emerging controversial publications of neuropsychiatric events in infants and adolescents treated with oseltamivir are scarcely reported. To date, little is known on the potential side effects of oseltamivir on the mother and the fetus. In particular, data are scarce on the transplacental transfer of oseltamivir in pregnant women. Thus, oseltamivir safety profile needs to be further evaluated with pharmacokinetic and transplacental transfer studies to derive firm conclusions and recommendations.
To date, only 1 study investigated the transplacental transfer of oseltamivir and showed a low transplacental transfer of oseltamivir, even at supratherapeutic concentrations of oseltamivir phosphate. However, no data were available regarding the transplacental transfer of oseltamivir carboxylate, the active metabolite of oseltamivir phosphate.
In view of the limited data currently available, we aimed to determine the transplacental transfer of oseltamivir and its metabolite, using the ex vivo gold standard method of the perfused cotyledon.
Materials and Methods
Materials
Term placentas (37-41 weeks of gestational age) collected from uneventful pregnancies were immediately collected (n = 5) after vaginal delivery. The enrolled patients did not receive any medication except for epidural analgesia or ocytocin during labor and did not present any vascular comorbidity such as diabetes mellitus, preeclampsia, or intra uterine growth restriction. Each patient gave a written informed consent prior to study inclusion. The study was approved by the local ethics committee.
The maternal and fetal solutions were prepared with Earle medium containing 2 g/L bovine serum albumin (Euromedex, Souffel Weyersheim, France). Oseltamivir phosphate (Op) and oseltamivir carboxylate (Oc) powder was provided by F. Hoffmann-La Roche Ltd (Basel, Switzerland).
The targeted maternal compartment concentrations of Op and Oc were around the maximal plasmatic concentration described in the literature for nonpregnant patients treated with a twice-daily oral dose of 75 mg (ie, 20 and 125 ng/mL, respectively).
Methods
Collected placentas were subsequently perfused in an open (nonrecirculating) double circuit according to the method initially described by Schneider et al subsequently modified as recently described. Perfusion experiments were started within 30 minutes after delivery. After a visual examination to confirm vascular integrity of both maternal and fetal sides, a distal branch of a fetal artery and its associated vein that were supplying a peripheral cotyledon were cannulated.
The fetal circulation was established at a flow rate of 6 mL/min. After confirmation of absence of vascular leakage, the perfused area progressively whitened, which allowed visualization of the selected cotyledon. The perfusion was subsequently initiated by insertion of 2 catheters into the intervillous space on the maternal side. The maternal circulation was established at a flow rate of 12 mL/min. The values of pH in maternal and fetal reservoirs were adjusted to 7.4 and 7.2, respectively.
Parameters such as perfusion pressure in the fetal vasculature and fluid leakage from the fetal to the maternal circulation are usually monitored to check the validity of the technique. This is determined during the experiment by controlling, in the fetal circuit, the balance of flows in the portions corresponding to the arterial and venous circulation. Similarly, perfusion pressure and its stability are measured during controlled experiment. Usually the values are between 40 and 60 mm Hg for the fetal circulation and between 10 and 20 mm Hg for the maternal circulation.
Combination of Op, Oc, and the freely diffusing marker antipyrine (Ap) were added into the maternal compartment for 90 minutes. Samples from the maternal reservoir were collected at 0, 30, 60, and 90 minutes, whereas samples from venous fetal circulation were collected every 5 minutes up to 90 minutes to assess Op and Oc concentrations.
Concentrations of Op and Oc were measured by liquid chromatography–mass spectrometry. Stable labeled isotopes ( H 5 -oseltamivir and CD 3 -oseltamivir acid) were used as an internal standard. Ten microliters of extract samples were injected onto a Chromolith performance RP18e, 100 × 3 mm analytical column using a Shimadzu LC system operating in a gradient mode.
The chromatographic method involved acetonitrile 0.1% formic acid and H 2 O 0.1% formic acid as mobile phases. The gradient ran from 10% to 90% organic phase in 2.5 minutes, and then the 90% organic phase was maintained for 1 minute, returning to initial condition in 0.1 min and up to 6 minutes run time. One milliliter per minute flow rate was used. An API 4000 mass spectrometer (Applied Biosystems, Courtaboeuf, France) with a turboion spray interface operating in positive ionisation mode was used for the multiple reaction monitoring analyses.
The analytes were detected by tandem mass spectrometry using the traditional multiple reaction monitoring of precursor-product ion transitions with 100 milliseconds dwell time, at a mass to charge ratio of 313.3/208.1 and 285.2/197.1 for oseltamivir and its corresponding acid and 318.2/203.2 and 289.4/201.2 for H 5 -oseltamivir and CD 3 -oseltamivir acid.
Data acquisition was performed using Analyst 1.4.2. (Applied Biosystems) and the quantification by Watson 7.2.0.03 (Thermo Electro Corp., San Jose, CA). The coefficient of variation for the measurement of Op and Oc at 0.1 ng/mL and 1 (lower limit of quantification) were 6% and 4 %, respectively.
Antipyrine concentrations were also measured by high-performance liquid chromatography, with ultraviolet detection at 290 nm. The mobile phase was a mixture of 0.05 mol/L phosphate buffer (pH 3)/methanol/tetrahydrofuran (75/25/0.9 [volume/volume per volume]). Standard curves were prepared with antipyrine concentrations ranging from 50 to 20,000 μg/L. Both within-day and between-days variabilities were 10% or less, and the lower quantification limit of antipyrine was 50 μg/L.
Two transport parameters were assessed during the study and calculated as follows: the fetal transfer rate (FTR) = (Cf/Cm) × 100, where Cf is the venous fetal concentration of drug and Cm is the maternal concentration of the same drug. The result was given as a percentage.
The clearance index (CI) = FTR (drug)/FTR (Ap), where FTR (drug) is the FTR of the studied drug and FTR (Ap) is the FTR of antipyrine.
Descriptive statistics were used and data were expressed as median (range) and mean (±SD).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
