Implementation of isoniazid preventive therapy in an HIV clinic in Cambodia: high rates of discontinuation when combined with antiretroviral therapy.

Objective: Data on feasibility and completion rates of isoniazid preventive therapy (IPT) in HIV-infected patient in Asia are limited. Within a hospital-based HIV programme in Phnom Penh, Cambodia, we determined the proportion completing IPT and reasons for non-completion.

Methods: Retrospective cohort study using HIV/IPT programme data, including all adults starting IPT (300 mg/day self-administered for 24 weeks) from February 2011 to March 2013. All patients underwent symptom screening and further investigations as indicated. After ruling out tuberculosis (TB), IPT was started, with monthly follow-up visits. As per national guideline, IPT was only prescribed for ART-naïve patients. IPT completion was defined as taking IPT for at least 22 of the planned 24 weeks. Stavudine/lamivudine/nevirapine was the preferential first-line ART regimen.

Results: Among 445 ART-naïve patients starting IPT (median age: 35 years (IQR: 31-43), median CD4 count 354 cells/μl (IQR 215-545) and 288 (65%) were female), 214 (48%) started ART after a median of 4 weeks (IQR 2-6) on IPT ('concurrent ART'). Overall, 348 (78%) completed IPT. Among individuals with concurrent ART, the completion rate was 73% (157/214). Those without concurrent ART had a higher completion rate (83%; 191/231; P 0.017). The main reason for non-completion with concurrent ART was drug toxicity (mainly hepatotoxicity/rash), occurring in 22% (48/214). Without concurrent ART, the main reason for non-completion was loss to follow-up (16/231; 7%). Fourteen (3%) patients were diagnosed with TB while on IPT, of whom three had a positive TB culture at baseline. An additional 14 TB cases were diagnosed after IPT completion; four were bacteriologically confirmed.

Conclusion: Although overall completion rates were acceptable, IPT discontinuation due to drug toxicity was common in patients subsequently initiating ART. Future studies should evaluate whether this relates to IPT, ARVs or both, and whether the increased toxicity would justify delaying IPT initiation until stabilisation on ART.