Estimating the cost effectiveness of atovaquone versus intravenous pentamidine in the treatment of mild-to-moderate Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia (PCP) is the most common severe opportunistic infection, and one of the most costly, among people with AIDS. Over 50% of patients experience toxic effects of the major anti-PCP medications- cotrimoxazole (trimethoprim-sulfamethoxazole) and pentamidine. Recently, the US Food and Drug Administration approved a new oral drug therapy, atovaquone, as an alternative to pentamidine for the treatment of people with mild-to-moderate PCP who are intolerant of cotrimoxazole. We developed a decision tree model to estimate the costs and cost effectiveness of atovaquone therapy compared with intravenous pentamidine therapy for cotrimoxazole-intolerant patients with mild-to-moderate PCP. Clinical outcomes were based on data from a phase III trial comparing the 2 medications. Our economic outcomes were based on treatment algorithms derived from discharge data, published reports and the clinical judgement of the co-authors. We estimate the total expected cost of treating a patient for an episode of PCP with atovaquone to be $US3990 compared with $US6545 for pentamidine under our baseline scenario (1995 dollars). Our decision model also provides insight into the large cost-savings benefits of treating mild-to-moderate PCP on an outpatient basis.