The safety of using prescription drugs in combination with other substances depends on a number of factors including the types of medications, dosages, other substance use (e.g., alcohol), and individual patient health factors. Patients should talk with their health care provider about whether they can safely use their prescription drugs with other substances, including prescription and over-the-counter (OTC) medications, as well as alcohol, tobacco, and illicit drugs. Specifically, drugs that slow down breathing rate, such as opioids, alcohol, antihistamines, CNS depressants, or general anesthetics, should not be taken together because these combinations increase the risk of life-threatening respiratory depression.4,26 Stimulants should also not be used with other medications unless recommended by a physician. Patients should be aware of the dangers associated with mixing stimulants and OTC cold medicines that contain decongestants, as combining these substances may cause blood pressure to become dangerously high or lead to irregular heart rhythms.27
