Drug Monitoring — SCE Dermatology MCQ

Correct answer: B — Peripheral neuropathy

The correct answer is B, peripheral neuropathy, which is the principal non-teratogenic, dose-limiting toxicity of thalidomide and the reason for mandatory pre-treatment and periodic neurological review. Thalidomide causes a length-dependent, predominantly sensory axonal neuropathy that is cumulative-dose related, insidious in onset (numbness and painful paraesthesiae in the feet and hands) and, critically, may become irreversible if the drug is continued once symptoms appear. Because of this, UK prescribing requires baseline clinical neurological assessment (with nerve conduction studies where indicated) before starting therapy and at regular intervals thereafter, with immediate cessation of thalidomide at the first sign of sensory symptoms or electrophysiological change. This distinguishes thalidomide's monitoring needs from other systemic agents used in recalcitrant cutaneous lupus erythematosus, where organ-specific toxicity (renal, hepatic) is more usually the concern. Why the other options are wrong: A. Nephrotoxicity: thalidomide is not renally toxic; nephrotoxicity monitoring is relevant to agents such as ciclosporin, not thalidomide. E. Hepatotoxicity: liver injury is not a characteristic or clinically significant adverse effect of thalidomide, unlike methotrexate or azathioprine. C. Pancreatitis: this is not a recognised thalidomide toxicity; it is associated with drugs such as azathioprine. D. Pulmonary toxicity: interstitial lung disease is a concern with agents like methotrexate, not thalidomide, which instead carries a venous thromboembolism risk rather than a pulmonary toxicity per se. Key point: Thalidomide's dose-cumulative, potentially irreversible sensory peripheral neuropathy mandates baseline and periodic clinical (plus nerve conduction where indicated) neurological monitoring, with immediate withdrawal at first symptoms.

Reference: electronic Medicines Compendium (emc), Thalidomide BMS 50mg Hard Capsules Summary of Product Characteristics, section 4.4/4.8 (peripheral neuropathy warnings and monitoring), medicines.org.uk/emc/product/6317/smpc