What test should be monitored in a patient taking theophylline?

What test should be monitored in a patient taking theophylline?

• A. Serum theophylline level
• B. Serum potassium level
• C. Liver function tests
• D. Complete blood count

Answer: (A)

The key idea is that theophylline has a narrow therapeutic window, so drug level monitoring is essential to stay effective without toxicity. Measuring the serum theophylline level lets you keep the concentration within approximately 10–20 mcg/mL and adjust dosing as needed. Levels can be affected by factors like age, liver function, and drug interactions (for example, certain antibiotics or other medications can raise theophylline levels). If the level climbs too high, toxicity can occur, presenting with symptoms such as nausea, vomiting, tachycardia, insomnia, and in more severe cases seizures. Other tests like potassium, liver enzymes, or complete blood count aren’t specific indicators for guiding theophylline therapy, so they’re not routinely used to monitor its effectiveness or safety.

The key idea is that theophylline has a narrow therapeutic window, so drug level monitoring is essential to stay effective without toxicity. Measuring the serum theophylline level lets you keep the concentration within approximately 10–20 mcg/mL and adjust dosing as needed. Levels can be affected by factors like age, liver function, and drug interactions (for example, certain antibiotics or other medications can raise theophylline levels). If the level climbs too high, toxicity can occur, presenting with symptoms such as nausea, vomiting, tachycardia, insomnia, and in more severe cases seizures. Other tests like potassium, liver enzymes, or complete blood count aren’t specific indicators for guiding theophylline therapy, so they’re not routinely used to monitor its effectiveness or safety.