erythromycin + theophylline

Erythromycin + theophylline is a combination of two small molecule drugs, each with distinct mechanisms of action. Erythromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, thereby preventing bacterial growth. Theophylline is a methylxanthine bronchodilator that works primarily by inhibiting phosphodiesterase enzymes, leading to increased intracellular cyclic AMP and resulting in relaxation of bronchial smooth muscle. This combination may be encountered in clinical practice when both drugs are prescribed concurrently for conditions such as respiratory tract infections (erythromycin) and asthma or chronic obstructive pulmonary disease (theophylline). However, co-administration can result in significant pharmacokinetic interactions; erythromycin can increase serum concentrations of theophylline by reducing its clearance, potentially leading to toxicity, while theophylline may decrease erythromycin levels through increased renal clearance[1][2][3][5].