While multiple factors determine the risk for a drug interaction, the number 1 predictor is the number of medications a patient is receiving. Nearly half of patients over 75 take at least five medications. Polypharmacy is a far greater issue in older compared with middle-aged patients, and increases the risk for drug interactions in the elderly. Pravastatin, which is not metabolized by the most common metabolic pathway, cytochrome P450 3A4, does not contribute to the risk for drug interactions. This differs from all of the other statins, which require metabolism through the P450 system to be eliminated.