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.
100 mg capsules
Indication: specified fungal infections
Itraconazole is a triazole which inhibits the synthesis of fungal cell membranes. It is best absorbed after food, but bioavailability varies. The pharmacokineticsmay be non-linear due to a saturation of metabolism.
The drug is highly protein bound with only 0.2% circulating as free drug. The concentration in the skin is usually higher than the plasma concentration. ltraconazole is extensively metabolised by the liver to inactive metabolites. The elimination half-life may increase with repeated dosing to over 24 hours.
Itraconazole is effective against superficial dermatophytes and Candidaalbicans. It has been approved for use in pityriasis versicolor unresponsive to other therapy and cases of superficial dermatomycoses, vulvovaginal candidiasis and fungal keratitis which have failed to respond to topical treatment. In immuno compromised patients, itraconazole has been approved for the treatment of oral candidiasis. The recommended duration of treatment varies from 3days for vulvovaginal candidiasis to at least 4 weeks in immuno compromised patients with oral candidiasis.
Whether itraconazole is more effective than ketoconazole is uncertain, but it is thought to be less toxic.1 Nevertheless, 15% of patients treated with itraconazole will experience an adverse reaction. These reactions are mostly gastrointestinal, but itraconazole can produce hypertension, hypokalaemia and ankle oedema probably due to an effect on the adrenal glands.
Interacting drugs which require itraconazole to be prescribed with additional caution include digoxin, phenytoin, H2 antagonists, warfarin, isoniazid, rifampicin, norethisterone and oral hypoglycaemic drugs. ltraconazole should not be prescribed with astemizole or terfenadine because of the potential for cardiac arrhythmias.
- Dismukes WE. Azole antifungal drugs: old and new. Ann Intern Med 1988;109:177-9.