A 68-year-old patient [sex not stated] developed reversible hallucinations and fatigue following therapy with clemastine. The patient had a history of metastatic osteosarcoma. The patient also had impaired renal function due to prior chemotherapy. The patient was receiving cetuximab. Later, the patient received antihistamine therapy with clemastine 2mg [frequency and route not stated] to avoid an allergic reaction to cetuximab. During first course of cetuximab therapy, the patient developed fatigue and reversible grade 2 hallucinations which were most likely caused by clemastine [duration of treatment to reaction onset and outcome not stated]. …