Which drug's therapeutic range is listed as 10-20 with toxicity above >20.0?

• A. Dilantin
• B. Theophylline
• C. Digitalis
• D. APAP

Answer: (A)

Dilantin, which is the brand name for phenytoin, is an anticonvulsant medication primarily used to manage seizures. Its therapeutic range is indeed between 10-20 mcg/mL, and levels above 20 mcg/mL indicate potential toxicity.

Monitoring the serum levels of Dilantin is crucial because it has a nonlinear pharmacokinetic profile, meaning that small increases in dose can lead to disproportionately larger increases in serum concentration. Within the therapeutic range, patients are more likely to experience the beneficial effects of the medication with minimal side effects, but once levels exceed 20 mcg/mL, side effects can become pronounced, leading to symptoms of toxicity, such as nystagmus, ataxia, and, in severe cases, respiratory depression or coma.

Understanding this specific therapeutic range is essential for safe pharmacological management in the clinical setting.