Browsing by Author "Fillekes, Quirine"

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    Pediatric Underdosing of Efavirenz: A Pharmacokinetic Study in Uganda
    (JAIDS Journal of Acquired Immune Deficiency Syndromes, 2011) Fillekes, Quirine; Natukunda, Eva; Balungi, Jackie; Kendall, Lindsay; Bwakura-Dangarembizi, Mutsa; Keishanyu, Rosette; Ferrier, Alex; Lutakome, Joseph; Gibb, Diana M.; Burger, David M.; Walker, A. Sarah
    Objectives: To evaluate international pediatric efavirenz dosing recommendations using full pharmacokinetic (PK) information. Design: Open-label, multicenter, PK study. Methods: Forty-one HIV-infected Ugandan children (3–12 years) on efavirenz + lamivudine + abacavir were enrolled in a study of twice-daily to once-daily lamivudine + abacavir 36 weeks after antiretroviral therapy initiation in the ARROW trial. Once-daily efavirenz doses were 200, 250, 300, 350 mg for children weighing 10 to ,15, 15 to ,20, 20 to ,25, 25 to ,30 kg, respectively, using 200/50 mg capsules or halved 600 mg tablets in case of 300 and 350 mg doses. Intensive plasma PK sampling (t = 0, 1, 2, 4, 6, 8, 12 hours postobserved ingestion) was performed at steady state (PK1) and repeated 4 weeks later (PK2, including a further 24-hour sample). Results: Forty-one and 39 children had evaluable efavirenz profiles at PK1 and PK2, respectively. Seventeen (41%) were boys. Five, 16, 17, 3 were in the 10 to ,15, 15 to ,20, 20 to ,25, 25 to ,30 kg weight bands. The geometric mean (%CV) the area under the concentration– time curve 0–24 hours postdose was 50.8 (90.8%) and 55.5 (82.7%) h$mg$L-1 at PK1 and PK2, respectively. Six children at PK1 and 7 at PK2 had subtherapeutic C8h and/or C12h (,1.0 mg/L), 7 of 41 (17%) at either visit. At PK2, 15 of 39 (38%) children had C24h ,1.0 mg/L (median (interquartile range) [range] 1.1 (0.7–2.9) [0.3–18.4]). Ten children at PK1 and 11 at PK2 had C8h and/or C12h .4.0 mg/L; 12 of 41 (29%) at either visit. Conclusions: African children aged 3–12 years, on efavirenz dosed according to 2006 WHO/manufacturer’s recommendations, had lower and highly variable efavirenz PK parameters compared with adult data from manufacturer’s leaflet. There were no differences across weight bands, suggesting no major effect of using half tablets. Higher pediatric efavirenz doses, as per WHO 2010 recommendations, should be used and investigated further but may risk increasing the proportion of children with potentially toxic levels.
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    Therapeutic drug monitoring of nevirapine in saliva in Uganda using high performance liquid chromatography and a low cost thin-layer chromatography technique
    (BMC Infectious Diseases, 2014) Lamorde, Mohammed; Fillekes, Quirine; Sigaloff, Kim; Kityo, Cissy; Buzibye, Allan; Kayiwa, Joshua; Merry, Concepta; Nakatudde-Katumba, Lillian; Burger, David; Rinke de Wit, Tobias F.
    In resource limited settings access to laboratory monitoring of HIV treatment is limited and therapeutic drug monitoring is generally unavailable. This study aimed to evaluate nevirapine concentrations in saliva using low-cost thin-layer chromatography (TLC) and nevirapine concentrations in plasma and saliva using high performance liquid chromatography (HPLC) methods; and to correlate nevirapine plasma concentrations to HIV treatment outcomes in Ugandan patients. Methods: Paired plasma and stimulated saliva samples were obtained from Ugandan, HIV-infected adults on nevirapine-based ART. Nevirapine concentrations were measured using a validated HPLC method and a novel TLC method. Plasma nevirapine concentrations <3.0 mg/L using HPLC were considered subtherapeutic. Negative/positive predictive values of different thresholds for subtherapeutic nevirapine concentrations in saliva were determined. Virologic testing and, if applicable, HIV drug resistance testing was performed. Results: Median (interquartile range, IQR) age of 297 patients was 39.1 (32.8-45.2) years. Three hundred saliva and 287 plasma samples were available for analysis. Attempts failed to determine nevirapine saliva concentrations by TLC. Using HPLC, median (IQR) nevirapine concentrations in saliva and plasma were 3.40 (2.59-4.47) mg/L and 6.17 (4.79-7.96) mg/L, respectively. The mean (coefficient of variation,%) nevirapine saliva/plasma ratio was 0.58 (62%). A cut-off value of 1.60 mg/L nevirapine in saliva was associated with a negative/positive predictive value of 0.99/ 0.72 and a sensitivity/specificity of 87%/98% for predicting subtherapeutic nevirapine plasma concentrations, respectively. Only 5% (15/287) of patients had subtherapeutic nevirapine plasma concentrations, of which 3 patients had viral load results > 400 copies/mL. Patients with nevirapine concentrations in plasma <3.0 mg/L had an Odds Ratio of 3.29 (95% CI: 1.00 – 10.74) for virological failure (viral load >400 copies/mL). Conclusions: The low-cost TLC technique for monitoring nevirapine in saliva was unsuccessful but monitoring nevirapine saliva and plasma concentrations using HPLC was shown to be feasible in the research/specialist context in Uganda. Further optimization and validation is required for the low-cost TLC technique.