Theophylline toxicity presents with which of the following symptom clusters?

• A. Skin rash
• B. Central nervous system symptoms such as headache, insomnia and seizures
• C. Nausea only
• D. Muscle weakness

Answer: (B)

The key idea is that theophylline toxicity causes central nervous system stimulation, often with seizures. Theophylline is a methylxanthine with a very narrow therapeutic window, so when levels rise it acts as a CNS stimulant by antagonizing adenosine receptors and inhibiting phosphodiesterase. This leads to symptoms like headaches, insomnia, agitation or tremors, and can progress to seizures. Those CNS symptoms—headache, insomnia, and seizures—best describe the classic toxic syndrome. Nausea and GI upset can occur, and tachycardia or other cardiac effects may accompany toxicity, but skin rash is not typical, and nausea-only or muscle weakness do not reflect the main toxic pattern.