9 Drug Interactions That Can Be Dangerous for Older Adults - GoodRx (2024)

As you get older — especially after the age of 65 — you may notice that you’re taking more medications. And with more medications comes more risk. Combining certain medications can raise your chances of side effects and drug interactions. While some of these effects may be mild, others can have serious consequences.

1. Multiple medications that can increase potassium levels

Potassium is an electrolyte that helps cells throughout your body function properly. Your kidneys help regulate your potassium levels, getting rid of any extra that your body doesn’t use. But as you age, your kidney function naturally declines. This can raise your risk for increased potassium levels (hyperkalemia).

Some of the most commonly used medications can increase potassium levels. Examples include many blood pressure and heart failure medications, immunosuppressants, and even antibiotics. Potassium supplements, which can be available over the counter (OTC), are another culprit. Taking more than one of these medications can be risky, especially for older adults.

If your potassium levels are higher than normal, you may initially have mild symptoms of fatigue, muscle weakness, or numbness. Nausea and vomiting are also possible. But if you notice any of these symptoms, you should notify your prescriber right away. At worst, hyperkalemia can lead to life-threatening cardiac arrest.

2. Opioids and benzodiazepines

Opioids, such as oxycodone, are prescribed for acute and chronic pain conditions. But opioids can cause serious side effects, such as excessive drowsiness and slowed breathing. These effects may be amplified in older adults. Benzodiazepines (BZDs), which are used for seizure and anxiety disorders, have similar side effects and risks in this age group.

Combining opioids and BZDs together can cause additive side effects, which can be harmful — even at seemingly appropriate doses. This combination can also make you feel weak or dizzy, increasing the risk of falls. Combining opioids and BZDs can even cause a life-threatening overdose.

Still, there may be times when your prescriber can’t avoid this combination. In these cases, it’s best to follow their directions. If you’re taking these medications as needed, they may have you take the lowest effective dose for the shortest time possible. Monitor yourself for symptoms such as symptoms of weakness, drowsiness, and slowed breathing. It’s also a good idea to have naloxone (Narcan) on hand, and to train caregivers or family members how to use it in case of an opioid overdose.

3. Opioids and gabapentin

Similarly to BZDs, gabapentin can also raise the chances of negative side effects with opioid medications. Gabapentin and similar medications, such as pregabalin (Lyrica), are often used for nerve pain and seizures. But one of their side effects is drowsiness, or sedation.

Combining opioids and gabapentin can increase the risk of sedation, slowed breathing, and falls. So this combination is generally avoided. But there may be situations where you’re prescribed both medications, such as if you’re transitioning from an opioid to gabapentin. In this case, your prescriber will provide guidance for how to take these medications safely.

4. Multiple anticholinergic medications

Anticholinergic medications treat a wide variety of ailments — from Parkinson’s disease to overactive bladder. There are hundreds of medications that have anticholinergic properties, meaning that they block a chemical called acetylcholine. Many common sleeping aids and allergy pills, such as Benadryl (diphenhydramine), also have anticholinergic effects.

There are a few reasons why anticholinergic medications can be risky for older adults. First, they can cause side effects such as confusion, dry mouth, and constipation, which can be more severe with age. These medications have also been linked to an increased risk of dementia and falls. Taking multiple anticholinergic medications can worsen these effects.

Overall, it’s best to avoid anticholinergic drugs — especially more than one — in older adults. Since many OTC medications fall into this category, it’s best to consult your healthcare team before taking one. They may be able to find an alternative medication without these effects. If needed, they may have you take an anticholinergic medication for only a limited amount of time.

5. Multiple CNS-active medications

Central nervous system (CNS)-active medications affect your brain and spinal cord. They’re used to treat several health conditions, such as depression, pain, and neurological disorders. Examples of CNS-active medications include:

• Antiepileptics

• Antidepressants

• Typical and atypical antipsychotics

• BZDs

• Hypnotics (“z-drugs”)

• Opioids

CNS-active medications can be risky in older adults, especially when they’re taken in combination with each other. In fact, there’s strong evidence showing a higher risk of falls and fractures if you take three or more of them.

Notify your prescriber if you’re concerned about the number of CNS-active medications you’re taking as some of these medications need gradual dose reduction over time. They can help you stop taking unneeded medications or provide alternatives.

6. Lithium and loop diuretics

Lithium is a mood stabilizer commonly used for bipolar disorder. It’s possible to have too much lithium in the body, resulting in lithium toxicity. This is one of the reasons why lithium requires careful drug level monitoring. However, older adults are at higher risk of lithium toxicity, even with normal blood levels.

What’s more, some medications can interact with lithium. Loop diuretics, such as furosemide, are one example. Taking lithium with furosemide can increase lithium levels in your body, raising the risk of lithium toxicity even more.

If you’re not able to avoid this combination, your prescriber may have you take a lower lithium dose. They’ll also keep a close eye on your lithium levels during treatment. Tell them right away if you experience symptoms such as nausea and vomiting, diarrhea, and tremors (shaking).

7. Warfarin interactions

Warfarin (Coumadin) is a medication used in people who have had a history of clots, atrial fibrillation, or valve replacements. It works by thinning your blood to prevent blood clots, but this can also increase the risk of bleeding.

Older adults tend to have a higher risk of severe bleeding with warfarin. And this risk goes up when it’s taken with other medications, including certain OTC products, that also cause bleeding or raise warfarin levels. Some medications that can increase the risk of bleeding with warfarin include:

• Aspirin

• NSAIDs

• Steroids, such as prednisone

• Fluconazole

• Ciprofloxacin, levofloxacin

• Sulfamethoxazole / trimethoprim (Bactrim)

• Selective serotonin reuptake inhibitors (SSRIs)

Other warfarin interactions may have the opposite effect and make warfarin less effective. This can increase the risk of blood clots. Examples of these medications include carbamazepine (Tegretol) and phenytoin.

Warfarin therapy requires regular blood tests to ensure your dosage is safe and effective. Even so, you’ll want to keep an eye out for any signs of bleeding or blood clots. Tell your prescriber if you notice bleeding gums with brushing or flossing, easy bruising, or bleeding from your nose or stools. Call 911 if you think you’re having a heart attack or stroke.

8. Phenytoin and bactrim

Phenytoin (Dilantin) is a medication that is used for seizure disorders. One downside is that it has a lot of drug interactions that increase phenytoin levels in the body. What’s more, older adults may not clear phenytoin from their system as well. This can result in too much phenytoin in the body, leading to adverse effects and potential toxicity.

Bactrim, which is commonly used to treat urinary tract infections (UTIs) and other bacterial infections, can interact with phenytoin. This combination can increase phenytoin levels in the body. If an alternative medication isn’t an option, your prescriber may watch your phenytoin levels closely. Tell them right away if you notice symptoms such as coordination problems, slurred speech, or sudden confusion.

9. Digoxin and antibiotics

While it’s not a first-choice medication, some people may be prescribed digoxin (Lanoxin). It’s sometimes used for heart rhythm problems and heart failure. Too much digoxin in the body can lead to toxicity, which may be more likely to happen in older adults. Interactions can raise this risk even more.

Several common antibiotics, including tetracyclines, erythromycin, and Bactrim, can interact with digoxin. When taken with digoxin, your digoxin levels may get too high — even with lower doses. This can cause symptoms such as nausea and vomiting, diarrhea, and vision color changes. Because of this, your prescriber may select a different antibiotic that doesn’t interact.

When should you contact your prescriber about a drug interaction?

It’s best to contact your prescriber about potential drug interactions up front. Many people turn to older adult specialists, or geriatricians, to manage their care. But since you may visit multiple providers, you’ll need to notify each of them of all the medications you’re taking. That way, they can avoid adding new medications that can interact with the old ones.

An easy way to do this is to carry a medication list with you to every appointment. You might also want to be informed of the potential interactions to avoid, in case something gets missed.