Which medication is NOT known to interact with theophylline?

Montelukast (Singulair) is a leukotriene receptor antagonist that is primarily used in the management of asthma and allergic rhinitis. It functions by blocking substances in the body called leukotrienes, which are involved in the inflammatory response in asthma. Theophylline is a methylxanthine that has a bronchodilator effect and is used for respiratory conditions such as asthma and COPD.

Montelukast does not have a significant pharmacokinetic interaction with theophylline, meaning it does not affect the metabolism or efficacy of theophylline in the same way that other medications do. This makes montelukast a suitable choice for patients being treated with theophylline, as it can be safely prescribed without the concerns that accompany other medications that interact with theophylline, affecting its clearance and increasing the risk of toxicity.

In contrast, erythromycin, phenytoin sodium, and cimetidine are known to interact with theophylline. Erythromycin can inhibit the hepatic enzymes that metabolize theophylline, leading to increased plasma concentrations. Phenytoin can alter the metabolism of theophylline, and cimetidine can also inhibit its metabolism, leading to similar increases in theophylline levels.