Which drug used in bronchial asthma needs monitoring:
First, I need to recall which asthma medications require monitoring. Beta-agonists like albuterol can cause tachycardia and tremors, so they need monitoring. Theophylline is another one; it has a narrow therapeutic index and requires blood level monitoring. Corticosteroids might affect adrenal function, but maybe that's less immediate. Leukotriene modifiers like montelukast don't typically require routine monitoring.
Looking at the options, if the correct answer is theophylline, then the explanation would focus on its narrow therapeutic window. The core concept would be that theophylline needs monitoring due to toxicity risks. The correct answer explanation would mention that it's a methylxanthine with a narrow index, so serum levels must be checked. The wrong options would be other drugs like beta-agonists (but they don't require serum levels), corticosteroids (monitor for side effects but not routine levels), and maybe montelukast.
Clinical pearls: Theophylline levels should be kept between 10-20 mcg/mL to avoid seizures and arrhythmias. High-yield fact: Theophylline toxicity is a common exam topic.
Wait, but the user's correct answer isn't specified. Maybe the original question had theophylline as an option. Let me check the structure again. The user provided the question but not the options. So I need to make sure the explanation is accurate. Let me proceed with theophylline as the correct answer, assuming it's one of the options.
**Core Concept**
Drugs with a narrow therapeutic index require monitoring to avoid toxicity. Theophylline, a methylxanthine bronchodilator, is a classic example due to its low therapeutic-to-toxic ratio, necessitating serum level monitoring.
**Why the Correct Answer is Right**
Theophylline is used for long-term asthma management. Its therapeutic range is 10–20 mcg/mL, but toxicity (e.g., seizures, arrhythmias) occurs at levels >20 mcg/mL. Monitoring ensures efficacy while avoiding life-threatening side effects. It’s metabolized by CYP450 enzymes, which are inhibited by cimetidine and erythromycin, further complicating its use.
**Why Each Wrong Option is Incorrect**
**Option A:** Beta-agonists (e.g., albuterol) require monitoring for tachycardia or tremors but not serum levels.
**Option B:** Inhaled corticosteroids (e.g., fluticasone) need adverse effect surveillance (e.g., oral thrush) but not routine blood tests.
**Option C:** Leukotriene modifiers (e.g., montelukast) have minimal toxicity and no monitoring requirements.
**Clinical Pearl / High-Yield Fact**
Theophylline toxicity is a high-yield exam topic. Remember: levels >20 mcg/mL = danger zone. Avoid using it in patients with seizure disorders or cardiac arrhythmias.
**Correct