This interaction can result in the accumulation of terfenadine and result in heart beat abnormalities. Also, interactions involving drugs with cumulative therapeutic effects, such as anti-anxiety medications taken at the same time with sleep medications, can cause excessive drowsiness and sleepiness. Other interactions involving drugs with cumulative side effects, such as antihistamines taken with a muscle relaxant, may cause excessive sedation. Drug-food interactions are also very important. Of course, alcohol and smoking can have a real effect on medications.
Smoking can speed up the rate at which some drugs are eliminated.
Alcohol can increase the potential harmful side effects of sleep and anxiety medications by causing excessive sedation and drowsiness. Alcohol, when taken with certain anti-diabetic medications, can cause facial flushing, nausea, vomiting, and tachycardia. It is both the patient's and the prescriber's responsibility to learn about the risks, as well as the benefits, of medications before they are prescribed and consumed.