Desensitization to methylphenidate--the relevance of continued drug intake for a successful outcome.

Methylphenidate is the treatment of choice in attention-deficit/hyperactivity disorder (ADHD). The authors report the case of a 7 year old boy with ADHD and psoriasis who developed generalised erythema, pruritus and fever 5 hours after the first oral administration of methylphenidate. After 2 days of treatment the drug was discontinued with complete resolution of symptoms. Later on, the drug was re-introduced with recurrence of the same clinical symptoms. Patch tests were performed with negative results. Desensitization was proposed and performed because there is no alternative treatment for ADHD. After the therapeutic dose was achieved, the mother interrupted drug intake because of a misunderstanding of instructions, and a mild rash subsided when another pill was administered. After this event the same desensitization procedure was carefully repeated. Interruption of drug intake during desensitization and consequent recurrence of clinical symptoms highlights the importance of continued exposure to the culprit drug in this kind of procedure. This modified protocol may enable patients with cutaneous reactions to this drug, to maintain therapy without recurrent reactions.