Principal Findings
In the intensive care unit of the US hospital, 58% of patients had at least one drug-drug interaction, while 16% had a clinically relevant drug-drug interaction. Significantly fewer patients had drug-drug interactions at the US hospital than the Pakistani hospital (58% vs. 95%, p < 0.01). Polypharmacy and length of stay increased drug-drug interaction occurrence in the US hospital (p<0.01).