Cambodians taking standard-dose (600-mg) efavirenz with rifampin for tuberculosis and weighing 50 kg or more attained lower efavirenz concentrations than those weighing less. But weighing 50 kg or more did not predict efavirenz concentrations below 1000 ng/mL or virologic failure.
Proper dosing of efavirenz in people taking rifampin-based anti-TB therapy remains a topic of intense study and debate. Researchers who conducted the Cambodian CAMELIA trial of early versus delayed antiretroviral therapy for people taking anti-TB regimens analyzed efavirenz concentrations in trial participants weighing more or less than 50 kg.
Six weeks after antiretroviral therapy began, plasma efavirenz concentrations were significantly higher in the 332 patients who weighed less than 50 kg than in the 150 patients who weighed 50 kg or more (median 2859 ng/mL, interquartile range [IQR] 1787 to 4749, in the lower-weight group, and 2060 ng/mL, IQR 1425 to 3575, in the higher-weight group, P = 0.02).
But the proportion of people with an efavirenz concentration below 1000 ng/mL did not differ significantly between the lower- and higher-weight groups (6% and 10%, P = 0.13).
Logistic regression analysis found no association between weighing more than 50 kg and efavirenz concentration below 1000 ng/mL. And efavirenz concentrations under 1000 ng/mL were not associated with virologic failure.
The CAMELIA team concludes that “current WHO guidelines recommending 600 mg efavirenz daily irrespective of patient’s body weight remains a safe and effective approach to treating coinfected adults needing simultaneous tuberculosis and HIV therapy.”
Source: Laurence Borand, Didier Laureillard, Yoann Madec, Monidarin Chou, Phearavin Pheng, Olivier Marcy, Thim Sok, Anne E. Goldfeld, Anne-Marie Taburet, François-Xavier Blanc, the CAMELIA (ANRS 1295-CIPRA KH001) study team. Plasma concentrations of efavirenz with a 600 mg standard dose in Cambodian HIV-infected adults treated for tuberculosis with a body weight above 50 kg. Antiviral Therapy. 2013; 18: 419-423.
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Source: IAS