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Stopping cotrimoxazole during antiretroviral therapy raises risk of bacterial illness, malaria, Ugandan trial shows
Keith Alcorn, 2015-02-26 01:10:00
Stopping cotrimoxazole prophylaxis increases the risk of
serious bacterial infections and malaria, even at high CD4 cell counts, in
people taking antiretroviral therapy in Uganda, results of a randomised trial
show. The results were presented on Wednesday at the Conference on Retroviruses and Opportunistic Infections (CROI 2015) in Seattle, USA, by Professor Jonathan Levin of the UK’s Medical Research Council.
Cotrimoxazole is a sulfa-based antibiotic that is used to
treat bacterial infections. Taken regularly, it provides protection, or
prophylaxis, against bacterial infections and also against malaria.
Cotrimoxazole prophylaxis is recommended for all adults with
HIV with CD4 cell counts below 350 and for all with symptomatic HIV disease
(WHO stages 3 or 4) regardless of CD4 cell count. Updated WHO guidance issued
in December 2014 recommended that cotrimoxazole prophylaxis could be stopped in
adults taking antiretroviral therapy if virally suppressed and showing evidence
of immune recovery. However, the guidelines noted that the quality of the
evidence to support this conditional recommendation was low.
But in settings where bacterial infections and malaria are
prevalent, cotrimoxazole prophylaxis can be continued regardless of CD4 cell
count, the guidelines state.
Long-term cotrimoxazole treatment increases the pill burden
for people taking antiretroviral therapy, which may compromise adherence, and
may also cause toxicity such as neutropenia (low levels of white blood cells
called neutrophils which fight off bacterial and fungal infections). It is also
an additional burden for pharmacies to manage cotrimoxazole stocks, and the
additional benefit for disease prevention in people on stable antiretroviral therapy in settings
with a high burden of bacterial infections is unclear.
In order to answer these questions, the Medical Research
Council designed a study to test whether it is safe to stop cotrimoxazole
prophylaxis in a setting with a high frequency of infections that are prevented
The COSTOP study randomised adults on antiretroviral therapy
with CD4 cell counts above 250 cells/mm3 to continue cotrimoxazole
prophylaxis or receive a placebo. The study was blinded to investigators and
participants. Ninety-three per cent of participants were followed for at least one year.
The study enrolled 2180 participants at two sites in rural
Uganda. Participants had a median CD4 count of 518 cells/mm3 and had
completed a median of four years of antiretroviral treatment.
The primary endpoints of the study were the time to death
or the first clinical event that was preventable by cotrimoxazole, and grade 3
and 4 haematological adverse events.
The study assessed efficacy by intent-to-treat analysis and
by a per-protocol analysis in which participants were evaluable if they had
taken at least 80% of their pills for each period between study visits.
After two years of follow up, the per-protocol analysis
showed significantly more primary endpoints in the placebo arm (2.94 per 100
person years vs 1.84 per 100 person years) (aHR 1.57, 90% confidence interval
The most frequently occurring events were bacterial
pneumonia (33 in the placebo arm vs 20 in the cotrimoxazole arm) and recurrent
urinary tract infections (4 vs 5). Six deaths were considered to be preventable
by cotrimoxazole, four in the placebo arm and two in the cotrimoxazole arm (one
of these was a case of malaria).
Haematological adverse events were significantly less
frequent in the placebo arm (10.6 vs 15.3 per 100 person-years, aHR 0.70, 90%CI
0.59-0.82). Severe neutropenia (grade 4) occurred in a substantial minority of participants in both arms of the study, but it was more frequent in the cotrimoxazole arm (8.2%
Malaria was significantly less frequent in those who
received cotrimoxazole (4.1 vs 13.9 cases per 100 person years, aHR 3.43, 95%
CI 2.69-4.38). Hospitalisation was also more frequent in the placebo group,
especially for malaria.
Cotrimoxazole recipients had significantly lower CD4 cell
counts (469 vs 495 cells/mm3) and were
more likely to experience no increase in CD4 cell count during the first 48
weeks of the study.