The cost-effectiveness of isotretinoin in the treatment of acne. Part 3. A cost-minimisation pharmaco-economic model.

OBJECTIVES The cost-effectiveness of systemic isotretinoin therapy in the treatment of moderate to severe acne was assessed in a comparative cost-minimisation analysis. Systemic isotretinoin at the recommended daily dose of 1 mg/kg (cumulative dose of 120 mg/kg) was compared with: (i) oral antibiotics taken as chronic medication; (ii) a combination of chronic oral antibiotics and anti-androgen therapy; and (iii) isotretinoin prescribed only after two failed courses of oral antibiotics, as per South African guidelines. The perspective taken was that of the funder of health care, and the resources used were funder charges as a proxy for costs. METHODOLOGY Statistical and epidemiological data as well as relevant costs from the previously reported meta-analysis and profiling study for acne therapy were used as the clinical basis for the construction of a cost-minimisation model. Additional costs were sourced from published pharmaceutical retail prices and professional rates. The South African treatment guidelines were used to define the frequencies associated with physician visits and pathology testing. Standard statistical methods were applied, as appropriate. From the above, a modified Markov process was used to model the costs associated with the four comparator treatment regimens over a period of 120 months. Suitable clinical and economic endpoints were defined so that comparison could be made between regimens. RESULTS Assuming a relapse rate of 21.45%, it was found that isotretinoin therapy compares favourably with the other regimens. After 50 and 35 months, systemic isotretinoin cumulative costs were less than those incurred in oral antibiotic and oral antibiotic/anti-androgen therapy, respectively. For the stepped therapy of oral antibiotics followed by systemic isotretinoin, these break-even periods were 56 and 39 months, respectively. The cost per successfully treated patient receiving isotretinoin was R8941. This compares well with the cost for those patients receiving chronic oral antibiotics, which after 5 years amounted to R10 428 per patient. Sensitivity analyses proved these findings to be robust to variations in the isotretinoin relapse rate, and the cost of oral antibiotic therapy and the concomitant use of topical therapies. CONCLUSION From the cost-minimisation model it is clear that where systemic isotretinoin is clinically indicated, the sooner such therapy is initiated the more cost-effective the outcome will be. If isotretinoin is prescribed on diagnosis of moderate to severe acne, then the cost of treatment is significantly reduced in the long term when compared with standard chronic oral antibiotic therapy.