The total costs of drug therapy for rheumatoid arthritis. A model based on costs of drug, monitoring, and toxicity.

Objective: We created a model to estimate the total medication costs of treating patients with rheumatoid arthritis with 6 second-line agents for the first 6 months of treatment.

Methods: Drug costs were obtained from a survey of pharmacies; monitoring costs were calculated from utilization information obtained in a survey of rheumatologists; toxicity costs were obtained using decision trees to represent the evaluation and treatment of potential toxicities. Monitoring and toxicity costs were estimated using costs from the Boston University Medical Center or, for hospitalizations, using appropriate diagnosis-related group categories. The sum of the 3 components determined the total medication costs.

Results: The least expensive medication was penicillamine, at $10.62/week, and the most expensive was injectable gold, at $30.89/week. In terms of monitoring costs, methotrexate had the highest costs associated with necessary laboratory tests and office visits. Hydroxychloroquine had the lowest monitoring costs for office visits, and oral gold had the lowest for laboratory costs. Hematologic toxicities were the largest component of toxicity costs for all 6 medications, and renal toxicities were costly for patients taking oral gold, penicillamine, and injectable gold. Total medication costs revealed oral gold as the least expensive medication and injectable gold as the most expensive. The combination of monitoring and toxicity costs accounted for more than 60% of the total costs for all medications except injectable gold. In all cases, the cost of treating toxicities was the smallest of the 3 components.

Conclusion: When calculating the costs of drug therapy, it is important to consider not only the price of the drug, but also the costs of monitoring and treating the toxicities that might occur. Failure to do so will result in underestimating the true costs of treatment with these medications.