The prevention of mother-to-child HIV transmission (MTCT) is a priority in Sub-Saharan Africa. A recent study has demonstrated that MTCT was reduced by 47% by providing a 200-mg dose of nevirapine to the mother at the onset of labor, followed by a 2-mg/kg dose of nevirapine suspension to the infant within 72 hours of birth.1 Due to simplicity and low cost, this nevirapine regimen has been widely promoted in developing countries for the prevention of MTCT. In the developing world, a high proportion of mothers do not deliver their babies in supervised health facilities. Women can obtain nevirapine tablets via antenatal services. However, many infants may not receive the pediatric dose because their mothers fail to return to health facilities for the postpartum medication. This service delivery problem was encountered in the rural Rakai District of southwestern Uganda, where only 30% of women have supervised deliveries, and most health facilities do not yet have access to nevirapine.2 In such a setting, it would be ideal to provide the nevirapine doses to the mother during pregnancy and teach her to self-medicate at onset of labor and administer the oral suspension to the infant after delivery. Such an implementation plan was evaluated by the Rakai Project in Uganda.3 During pregnancy, mothers were given a dosing kit containing a 200-mg tablet and an oral syringe containing 6 mg/0.6 mL of nevirapine suspension (dose of 2 mg/kg based on median birth weight) with dosing instructions. Dosing instructions are that the mother should take the tablet at the onset of labor and give the oral suspension to the infant within 72 hours after delivery. These kits are dispensed to mothers up to 3 months before expected date of delivery.
Nevirapine is marketed as Viramune by Boehringer Ingelheim Pharmaceuticals, Inc. Viramune Oral Suspension is supplied in 240 mL white high density polyethylene (HDPE) bottles with a recommended storage range of 15°C to 30°C. Nevirapine suspension presents special challenges not usually encountered with other oral liquid preparations. Nevirapine suspension is very viscous and clings tenaciously to a medicine cup or spoon. This property makes it difficult to accurately measure and administer small doses required for infants. The manufacturer recommends the suspension be administered with an oral dosing syringe, particularly for small volumes as are being used in MTCT programs.4 Stability data were not available for repackaged nevirapine in unit dose syringes at the time the study was performed. We undertook the following study to determine whether a single dose of nevirapine in an oral syringe was stable over time under varying storage conditions.
One hundred oral syringes were prepared from a 240-mL bottle of Viramune (50 mg/5 mL, lot number 157568A, Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, CT) using an Adapta-Cap Bottle Adapter (Baxa Corporation, Englewood, CO). The oral syringes were filled to contain 0.6 mL nevirapine. The oral syringes used were 3 mL amber Baxa Exacta-Med Oral Dispensers (lot number B85176, Baxa Corporation, Englewood, CO). The syringes were capped with Baxa Exacta-Med Dispenser Tip Cap (Baxa Corporation, Englewood, CO). A baseline median concentration of nevirapine was determined on 12 aliquots of the original lot of Viramune suspension. Eighteen syringes were then placed in 5 storage conditions: room temperature (26°C) with high relative humidity (RH) maintained by a water bath, high temperature with high RH (40°C, incubator with water tray), high temperature with low RH (40°C oven with Drierite [W.A. Hammond Drierite Company Ltd., Xenia, OH], average 14% RH), refrigerated (0-8°C), and frozen (−30°C). These conditions were chosen to reflect the diversity of storage environments in developing countries.
Nevirapine concentrations were measured on 3 samples from each storage condition monthly for 6 months. Nevirapine concentration was measured with high performance liquid chromatography (HPLC) using a modified validated nevirapine assay.5 The nevirapine assay is linear over the range of 25 ng/mL to 10,000 ng/mL. The intraday precision was ≥96% and accuracy was ≥93%. The interday precision was ≥93% and accuracy was ≥97%.
At each time point (0, 1, 2, 3, 4, 5, and 6 months) the concentration of nevirapine was determined in the following manner. At time zero, 2 aliquots from 6 syringes of the original lot of Viramune suspension were analyzed for nevirapine concentration. In addition, nevirapine concentrations were determined at each month (1-6 months) on triplicate syringes from each test condition. The syringes were allowed to equilibrate to room temperature before analysis.
A positive displacement pipette was used to obtain 100 μL aliquots from each sample syringe; these were placed in labeled 13 × 100 mm disposable culture tubes and diluted to 1 mL with methanol to produce solutions A. Next, 50 μL of each solution A was transferred to a clean 13 × 100 mm tube and diluted to 1 mL with methanol to create solutions B. Then 200 μL of each solution B was pipetted into a 15-mL polypropylene conical tube and diluted to 5 mL with mobile phase to create solution C, calculated to contain 2000 ng/mL nevirapine. A portion (50 μL) of each solution C was transferred into an Alliance vial containing 50 μL internal standard (described previously) and 50 μL HPLC-grade water; 125 μL was injected onto the HPLC system.
Each month the mean nevirapine concentration was determined from the 3 syringes obtained at each storage condition. To account for interassay variation, monthly calibrators were standardized against the baseline calibrator concentrations. Using these baseline-standardized calibrator concentrations, the estimated standardized nevirapine concentrations at monthly intervals were determined for the 5 storage conditions. The mean and standard deviations (SDs) were estimated, and the absolute change at 6 months relative to baseline was calculated. To assess trends in concentration over time, we fitted a linear regression of standardized nevirapine concentrations over 6 months.
Nevirapine samples from the oral syringes were cultured for anaerobic microorganisms in thioglycolate broth for 7 days and for aerobic microorganisms on chocolate blood agar for 3 days at the 3-month time point after samples were assayed for nevirapine. At 4 and 6 months, the oral syringes were tested for aerobic microorganisms on chocolate blood agar before nevirapine analysis.
Figure 1 graphically displays the nevirapine concentration trends over the 6-month period. The data clearly shows that at 40°C with low RH, after 3 months, there is a statistically significant increase in the concentration of nevirapine. The remaining storage conditions show statistically insignificant declines (≤8.7%) in nevirapine concentration from time zero. Room temperature with high RH, refrigeration and freezer storage were nearly identical to one another and to baseline, with declines of <3%.
Nevirapine samples, taken from the syringes after the drug assay was done, were tested at 3 months for microbiological growth on chocolate blood agar plate for aerobes and in thioglycolate broth for anaerobes. The cultures were negative for anaerobes and positive for normal aerobic skin flora. The 4-month and 6-month samples were plated on chocolate blood agar before manipulation for drug assay and results were negative for all pathogens.
The temperature and humidity ranges chosen for the study are representative of the diverse storage and environmental conditions possible in developing countries. Baxa 3-mL syringes were used instead of 1-mL syringes because when the dose is dispensed and capped, the 3-mL syringes are more compact, durable, and discreet. This is essential to withstand possible adverse transport and storage conditions. Small doses can be accurately measured because 3 mL Baxa Exacta-Med Oral Dispensers (Baxa Corporation, Englewood, CO) are calibrated in increments of 0.1 mL.
This study demonstrates that Viramune suspension can be packaged in 3-mL amber Baxa Exacta-Med Oral Dispensers (Baxa Corporation) and remains stable and free from bacterial contamination for at least 6 months, when stored at room temperature/high RH, high temperature/high RH, refrigerated or frozen. At high temperature and 14% relative humidity, the samples became more concentrated presumably due to evaporation from the Baxa Exacta-Med Oral Dispensers (Baxa Corporation). These syringes lost aqueous content rendering the suspension even more viscous, and were difficult to assay. The drug assayed for this condition showed that the suspension was more concentrated. However, due to the nature of the drug, sampling, and not anticipating this problem, we cannot affirm with any certainty that the nevirapine is stable under this condition. Therefore, given the volume loss and viscosity problem we do not recommend storing the syringes in environments with high temperature and extremely low relative humidity for more than 3 months. The Rakai Health Sciences Program has found that maternal self-medication at the onset of labor with a nevirapine tablet plus maternal provision of single-dose nevirapine suspension to the infant can reduce mother-to-child HIV transmission.3 This suggests that a MTCT dosing kit containing single doses of nevirapine tablet and nevirapine suspension is a feasible means of delivering this drug in circumstances in which women do not give birth in medical facilities, or find it difficult to visit such facilities postpartum.
This research was supported by the Elizabeth Glaser Pediatric AIDS Foundation. Baxa Corporation, Englewood, CO) donated the Baxa Exacta-Med Oral Dispensers used for the study.
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