Intrapartum Magnesium Sulfate and the Potential for Cardiopulmonary Drug-Drug Interactions

Background: This study sought to determine the frequency of possible cardiopulmonary drug-drug interactions among pregnant women who received intrapartum magnesium sulfate (MgSO4). Methods: Pregnant women admitted to an Intermountain Healthcare facility between January 2009 and October 2011 were studied, if they received 1 or more doses of MgSO4. Concomitant medications were electronically queried from an electronic health records system. Adverse events were identified using administrative discharge codes. The frequency of cardiopulmonary drug-drug interactions was compared among women who did, and did not, receive aminoglycoside antibiotics, antacids/laxatives, calcium channel blockers, corticosteroids, diuretics, neuromuscular blocking agents, and vitamin D analogs, all of which were contraindicated for patients receiving MgSO4. Results: Overall, 683 women received intrapartum MgSO4 during the study period. A total of 219 MgSO4 potentially interacting drugs were identified among 155 (23%) unique patients. The most commonly identified potentially interacting agents included calcium channel blockers (26%), diuretics (25%), and antacids/laxatives (19%). Longer hospital stays were significantly associated with increasing numbers of MgSO4 interacting drugs (P < 0.001). Three of 53 (6%) women who received furosemide experienced a cardiac arrest, compared with 0 of 618 (0%) women who did not receive furosemide (Fisher exact test, P < 0.001). Conclusions: Intrapartum administration of drugs that interact with MgSO4 is common and associated with prolonged hospital stays and potentially cardiopulmonary drug-drug interactions. Caution is warranted when prescribing MgSO4 in combination with known interacting medications.