3 Drug Combinations You Should Avoid, Discovered While Working at a Pharmaceutical Company

Have you ever picked up an over-the-counter medicine at a pharmacy and wondered, "Is it okay to take this with the medicine I just took?"

In fact, depending on the combination, some "drug interactions" can make the medicine's effects too strong or, conversely, render it ineffective. As an active drug discovery researcher working at a pharmaceutical company, I will introduce three combinations that you should be particularly careful about.

1. Cold medicine + antipyretic analgesic (double intake of acetaminophen)

Over-the-counter cold medicines contain acetaminophen, which I also introduced in my previous article. Some people take additional Loxonin or Bufferin because they have a fever and a headache, but this is dangerous.

Excessive intake of acetaminophen puts a heavy burden on the liver. While over-the-counter drug dosages are designed to be within a safe range, taking multiple medicines can cause you to exceed the upper limit without realizing it.

When you are taking cold medicine, be sure to check the ingredient list before adding another analgesic.

2. Hay fever medicine + alcohol (antihistamine x alcohol)

The antihistamines introduced in the previous article will have their drowsiness-inducing effects significantly enhanced when taken with alcohol.

Alcohol itself has a central nervous system depressant effect, which creates a synergistic effect with the drowsiness caused by antihistamines. Even if you only have "one drink because you've taken your medicine," the drowsiness may persist until the next morning, or your reflexes may become dulled. Driving a car is particularly dangerous.

As a general rule, avoid drinking alcohol on days when you take antihistamines.

3. Grapefruit + certain blood pressure/cholesterol medications (CYP3A4 inhibition)

This is a slightly more technical topic, but as a drug discovery researcher, it is a combination I want you to be especially aware of.

A component in grapefruit called furanocoumarin inhibits the function of the drug-metabolizing enzyme "CYP3A4" in the liver. This enzyme plays a role in breaking down many drugs in the body, and when its function is inhibited, the blood concentration of the drug rises higher than expected.

This is particularly true for blood pressure medications (calcium channel blockers) and cholesterol medications (statins). There is a risk that the medication will be too effective, causing blood pressure to drop too low, or increasing the risk of rhabdomyolysis, a condition where muscles break down.

Grapefruit juice has the same effect, so those taking these medications need to be careful.

Summary: Things to remember about drug interactions

• Be careful of acetaminophen overdose when combining cold medicine with other analgesics

• Antihistamines and alcohol have a synergistic effect that increases drowsiness

• Grapefruit can potentially raise the blood concentration of certain drugs too high

• When in doubt, it is best to check with a pharmacist or doctor

When used correctly, medicine is a powerful ally. However, if you get the combination wrong, it can lead to unexpected risks. People often assume that over-the-counter drugs are safe enough to use at their own discretion, but dangerous drug interactions can occur even with these medications.

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