Patients have been warned be mindful about possible interactions between their prescription medication and over-the-counter (OTC) drugs. Almost seven in ten Americans are on at least one prescription medicine, according to researchers at the Mayo Clinic and Olmsted Medical Center. A leading pharmacist has warned interactions between supplements, over-the-counter meds and prescription drugs are a "big problem" and urged patients to take steps ensure they are not at risk. 

"[There are] several OTC products that may be safe for some patients, but not all," pharmacist Bri Morris, director of strategic initiatives at the National Community Pharmacists Association, told NewsMaxHealth. The US Food & Drug Administration (FDA) urges patients to always read medication labels, adding that warnings and interaction details may change as new information becomes known. FDA interaction guidelines note labels will explain: what the drug is for, how it should be administered, and how to reduce the risk of interactions and side effects. However, it added patients with any concerns about their medication should ask a doctor or pharmacist for more information. 

The problem of drug interactions may be mitigated by patients taking advantage of the medication management programs run by many pharmacies, Morris suggested. "A pharmacist will sit down with a patient and go through records to make sure they have the full picture of the patient's medications and use of OTC products, and then share that information with the patient's health care providers," she explained. 

We've listed five drug classes with some  interactions patients should watch out for below. This is not exhaustive list of interactions and there may be other potential side effects and drug interactions to consider. If you are concerned about your combination of medications, speak to a pharmacist or your physician.

Antibiotics

• Antibiotics may reduce the effectiveness of birth control
• Effectiveness of the antibiotics may be reduced by some nutritional supplements, such as calcium or magnesium.

Antidepressants

• Nonsteroidal anti-inflammatory drugs (NSAIDs) such as Advil (ibuprofen) or naproxen might cause internal bleeding
• Combining these medications may also cause a change  in the body's levels of serotonin, a mood-stabilizing hormone.

Antihistamines

• May interact with sedatives, tranquilizers. 
• Prescription drugs for treating hypertension or depression may interact with antihistamines.

Opioids

• Patients on opioid prescriptions such as Percocet (oxycodone, acetaminophen) should be particularly careful about drug interactions, particularly with: alcohol, muscle relaxants, anti-anxiety medication and sleeping tablets.
• Painkillers with acetaminophen (such as Tylenol) may cause dangerous levels of acetaminophen in body when combined with certain opioids. 

Statins

• Statins such as Lipitor (atorvastatin) are among the most commonly prescribed drugs in the US, but there are many possible interactions to watch out for, including: antibiotics, HIV drugs and antidepressants.
• Some supplements and natural substances may also interfere with statins, such as the B vitamin niacin and potentially grapefruit juice.