Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Wellvone (Wellcome Australia)
250 mg film coated tablets
Indication: Pneumocystis carinii pneumonia
Immuno compromised patients, including those with HIV infection, are at risk of developing Pneumocystis carinii pneumonia. The pneumonia is usually treated with trimethoprim/sulfamethoxazole and this combination can be used as prophylaxis against recurrent infections. However, many patients with AIDS cannot tolerate trimethoprim /sulfamethoxazole. Pentamidine is one alternative treatment, but the majority of patients develop adverse reactions. Patients who are intolerant of trimethoprim/sulfamethoxazole can now be treated with atovaquone.
Atovaquone is an antimalarial drug which also has activity against Pneumocystiscarinii and Toxoplasma gondii . It acts by inhibiting electron transport in protozoal mitochondria.
The bioavailability of atovaquone is low, but absorption can be increased by taking the drug with food, especially high fat food. Atovaquone is mainly excreted unchanged in the faeces. The half life is approximately 3 days.
A double blind trial has compared atovaquone with trimethoprim/sulfamethoxazolein patients with AIDS and Pneumocystis carinii pneumonia. After 21 days, significantly more patients taking atovaquone had failed to respond to treatment. One month after therapy, mortality was significantly higher in the atovaquone group. Although atovaquone was less effective, it produced fewer treatment limiting adverse effects.1
Atovaquone has also been compared with intravenous pentamidine. Although more patients taking atovaquone failed to respond, the group had fewer treatment limiting adverse effects and more patients were improved one month after treatment.2
The most common adverse effect is rash. Other adverse reactions include nausea, vomiting, diarrhoea, headache, insomnia and fever. Information about drug interactions is limited, but plasma concentrations of atovaquone are significantly decreased by metoclopramide and rifampicin. Although zidovudine does not appear to affect the pharmacokinetics of atovaquone, zidovudine metabolism may be decreased by atovaquone.
