Many of us have become so accustomed to seeing the “avoid alcohol” warning on every new prescription we get that we’ve begun to tune out this advice…and few of us even consider that alcohol might react with over-the-counter (OTC) medications.

That’s a huge mistake! Alcohol is a powerful drug that has widespread and sometimes unpredictable effects in the body. It makes some medications less effective…amplifies the effects of others…and can cause a toxic—or even fatal—reaction with some medications.

Below, some medications that are adversely affected by alcohol…*

Acetaminophen

Acetaminophen (Tylenol) by itself can be harmful to the liver—in fact, acetaminophen overdose is the number-one cause of acute liver failure. But the likelihood of liver failure is much greater if you also drink alcohol.

Why acetaminophen and alcohol don’t mix: Alcohol is a toxin, but there’s a reaction in the body that breaks apart alcohol molecules so they are less dangerous. This reaction requires a coenzyme called NAD (nicotinamide adenine dinucleotide) that’s found in all living cells. However, we also need NAD to deal with the toxic effects of acetaminophen. The breakdown of acetaminophen in the liver creates a highly toxic by-product.

Main danger: If stores of NAD are depleted by drinking alcohol and taking acetaminophen, liver problems or even permanent liver damage can result. Acetaminophen is particularly dangerous when taken during or within a couple hours of alcohol consumption.

Ibuprofen

Ibuprofen (Advil, Motrin) blocks the production of prostaglandins. These hormones, which the body releases in response to illness and injury, can cause pain, swelling and fever. But prostaglandins also play a critical role in blood clotting and blood vessel control, which impacts kidney function.

When blood flow to the kidneys is reduced for any reason—for example, during exercise or dehydration—prostaglandins are released to prompt blood vessels in the kidneys to dilate, which helps protect them from oxygen deprivation.

Why ibuprofen and alcohol don’t mix: Drinking alcohol causes excess urination that can lead to dehydration. Alcohol also inhibits prostaglandins. If you take ibuprofen to help relieve a hangover or use it on an ongoing basis while drinking excess alcohol, it could block the prostaglandins that are released to protect the kidneys.

Main danger: Every episode of alcohol plus ibuprofen potentially kills a few more kidney cells, which makes kidney failure more likely over time. But acute renal failure can occur with just one episode of excess alcohol and ibuprofen.

Note: Ibuprofen combined with dehydration from diarrhea, vomiting or exercise, for example, can adversely affect the kidneys as well.

Blood Thinners

Aspirin and other blood thinners, such as warfarin (Coumadin) and clopidogrel (Plavix), are often used by people who have heart disease. They work by inhibiting prostaglandins, which, as mentioned above, are involved in blood clotting.

Why blood thinners and alcohol don’t mix: Because alcohol also inhibits prostaglandins, this combination results in an exaggerated anticlotting effect.

Main dangers: A higher, unpredictable anticoagulant effect in the system, which could cause dangerous bleeding anywhere in the body, such as a stroke or bleeding ulcer. Additionally, both aspirin and alcohol are known stomach irritants. Over time, the combination can increase the risk for stomach problems including gastritis and ulcers.

Anxiety Meds or Narcotics

Benzodiazepines (such as Valium and Xanax) and the narcotic pain relievers oxycodone (OxyContin) or hydrocodone (Vicodin) target specific neurotransmitter receptors in the brain. When triggered, these receptors depress brain activity, which helps ease anxiety and pain.

Why anxiety medications or narcotics and alcohol don’t mix: Alcohol is also a central nervous system depressant. If it’s consumed when either drug is still in a person’s system, the drug effect is amplified.

Main danger: The circuit in the brain that’s responsible for regulating breathing contains gamma-aminobutyric acid (GABA) neurons. When there’s excessive activation of GABA—which can happen when mixing these drugs and alcohol—the breathing circuits can shut down.

If you are unconscious—passed out or sleeping—you could stop breathing if you’ve had anxiety or pain medications and alcohol. These combinations are a major cause of alcohol-related deaths.

Blood Pressure Drugs or Viagra

There are two main types of drugs prescribed for high blood pressure—diuretics, such as chlorothiazide (Diuril), and vasodilators, such as nitroglycerin. Diuretics work by reducing blood volume, namely by ridding the body of excess water via urination. Vasodilators work by widening the blood vessels to lower blood pressure. Viagra, a drug used to treat erectile dysfunction, is a vasodilator as well.

Why blood pressure drugs or Viagra and alcohol don’t mix: Since alcohol is a diuretic and a potential vasodilator, it intensifies the actions of blood pressure medications and Viagra. In other words, combining alcohol and any of these drugs is like taking multiple doses of the medications.   

Main danger: You can have a dangerous drop in blood pressure that may cause dizziness, fainting, seizures or cardiac arrhythmias.

Alcohol and Other Meds

The effects of alcohol aren’t limited to the drugs listed above. The cytochrome P450 system in the liver helps the body to eliminate all foreign substances—alcohol, prescription and OTC drugs and pesticides. The more foreign substances you’re exposed to, the more robust this system becomes. Heavy drinkers have a very hearty cytochrome P450 system—this helps them detoxify large amounts of alcohol but also clears desirable drugs. This means a heavy drinker may not get the full benefit of any medication!

*It’s best to abstain from alcohol when taking any of these medications. However, if you do drink alcohol while taking these meds, be sure to accurately report the amount to your doctor so that you can be appropriately monitored.