Commonly used over-the-counter medications can cause interaction problems with certain prescriptions. To avoid dangerous over-the-counter drug interactions, you should consult a pharmacist or doctor before you take prescription drugs and OTC drugs at the same time. People who have chronic disorders should also consult a pharmacist or doctor.
Also, normal aging changes the speed and ways in which the body metabolizes drugs. Older people tend to have more diseases and to take more than one drug at a time. For these reasons, older people may be more likely than younger ones to experience drug interactions. Professionals estimate that one in four hospital admissions of seniors result from medication problems including prescription drugs interactions. Many times, health care practitioners may not think of asking about use of OTC drugs or medicinal herbs when they are prescribing or dispensing a prescription.
http://www.myoptumhealth.com/portal/DrugGuide/Interactions+Calculator is an excellent resource for checking prescription drugs interactions. It includes interactions between prescription drugs, over-the-counter medications, dietary supplements (both herbal and mineral) and various foods. Here is a list of possible OTC and drug interactions:
Aspirin can modify the effectiveness of arthritis medications, strong prescription steroids and diuretics. Combining aspirin with diabetic medications can drop blood sugars to dangerous levels. Aspirin can also cause toxicity when taken with glaucoma and anticonvulsant (anti-seizure) drugs and cause bleeding episodes when combined with a blood thinner, like Coumadin.
Acetaminophen can also cause interaction complications when overused. Heavy drinkers who take acetaminophen for hangover relief risk liver damage. Taking high doses of acetaminophen with Coumadin can cause bleeding episodes.
Antacids taken with antibiotics, heart and blood pressure or thyroid medications can decrease drug absorption by up to 90 percent.
Over-the-counter antihistamines (sold under the names Actifed, Theraflu, Dimetapp, Benadryl and Comtrex) should be avoided if you are taking antianxiety or antidepressant medications.