Verapamil interactions to avoid

Drug interactions | Food interactions | Other interactions | Avoiding interactions | When to see a doctor

Verapamil is well-known in the field of cardiology. However, it can come with undesirable side effects in the form of medication interactions. As a calcium channel blocker, this medication has been used for many years to manage heart rate in individuals with atrial fibrillation, atrial flutter, or supraventricular tachycardia (SVT). These conditions involve heart arrhythmias that can lead to a dangerously fast heartbeat and other abnormal heart rhythms. By blocking calcium channels in the muscular walls of blood vessels, verapamil is also an effective treatment for high blood pressure (hypertension) and angina forms of chest pain. Besides these indications approved by the U.S. Food and Drug Administration (FDA), it is used off-label for migraine and cluster headaches. This means that people in many different health situations can take verapamil, so knowing how this drug alters the metabolism of other drugs and foods can be critically important. You can avoid a negative outcome from verapamil therapy if you are aware of, recognize, and notify your healthcare provider of these interactions as soon as possible.

RELATED: Verapamil side effects and how to avoid them

Verapamil drug interactions

Most of verapamil’s significant interactions with other drugs stem from its inhibition of the CYP3A4 enzymes or its reliance on metabolism by this liver enzyme. The entire list of interactions is extensive and beyond our goals here, but highlighting the most important ones is our intent.

CYP3A4 enzyme substrates

Drugs that depend on the CYP3A4 enzyme can have their levels raised by being taken with verapamil. This interaction poses a danger of adverse or altered effects. Examples of these medications include:

• Relpax (eletriptan)
• Xanax (alprazolam)
• Valium (diazepam)
• Latuda (lurasidone)
• Abilify (aripiprazole)
• Cymbalta (duloxetine)
• Trazodone
• Buspirone
• Xarelto (rivaroxaban)
• Eliquis (apixaban)
• Plavix (clopidogrel)
• Erythromycin
• Roxicodone (oxycodone)

If you are taking one of these drugs or another drug metabolized by the CYP3A4 enzyme, you should double-check with your healthcare provider about the safety of starting verapamil. If you find yourself already taking such a drug along with verapamil, asking for medical advice is still advisable to make sure that nothing is being overlooked. The drugs on the list include ones with sedating effects, like opioids and antipsychotics, and blood thinning effects, like anticoagulants and antiplatelet agents, so the fallout from excess drug action could be disastrous. 

Statins

Statins are the most commonly used cholesterol-lowering drug class, and as such, you often see them used in the setting of heart problems, when verapamil may also be used. The two meds both inhibit CYP3A4 enzyme actions and amplify the adverse effect likelihood of one another. In other words, if you are taking a statin and verapamil is suggested, you should question your healthcare provider on whether an alternative or a dosage adjustment is necessary. This issue mainly pertains to Lipitor (atorvastatin), Zocor (simvastatin), and lovastatin. Ask the prescribing healthcare professional for medical advice to see if a different statin might be better.

CYP3A4 enzyme inducers

Drugs that induce the CYP3A4 enzyme accelerate the metabolism of verapamil, making it less effective. As a therapy for serious heart problems, a drop off in verapamil action can be quite detrimental. The anticonvulsants Mysoline (primidone), Tegretol (carbamazepine), and Dilantin (phenytoin), as well as the antibiotic Rifadin (rifampin), fall into this category. Your medical provider may want to change to a verapamil alternative, tweak the dose of verapamil, or closely monitor for an irregular heartbeat.

Heart rate and rhythm drugs

Verapamil is a negative chronotrope, meaning it reduces heart rate, and combining it with other negative chronotropes can set you up for bradycardia, a dangerously slow heart rate. Beta blockers, antiarrhythmics, and other calcium channel blockers are some of the more common drugs that can do so. Examples of these medications include:

• Inderal LA (propranolol extended-release)
• Toprol XL (metoprolol)
• Pacerone (amiodarone)
• Flecainide
• Quinidine
• Norvasc (amlodipine)
• Procardia XL (nifedipine extended-release)
• Lanoxin (digoxin)

Lithium

Keeping the mood stabilizer lithium at a safe and effective level is of utmost importance in the treatment of bipolar disorder. Verapamil can disrupt this tenuous balance. Accordingly, your psychiatrist may need to monitor lithium levels more closely, or your cardiologist may need to look for an alternative to verapamil. 

If drug cost keeps you from switching, there are regular and extended-release generic alternatives to verapamil’s higher-priced brand names, Verelan and Verelan PM. SingleCare’s prescription discount card and coupons could also assist you in lowering your pharmacy expenses.

Verapamil food interactions

Verapamil can be taken with or without food. If you are taking it for blood pressure control, you should limit sodium intake to help with managing your hypertension. Grapefruit is one food that warrants specific attention when consumed with verapamil.

Verapamil and grapefruit

Grapefruit juice affects the CYP3A4 enzyme, reducing its ability to metabolize verapamil and other drugs. As a result, drinking grapefruit juice can lead to toxicity and more adverse effects of verapamil, such as edema (lower leg swelling), constipation, bradycardia, and hypotension (abnormally low blood pressure). Your medical provider may suggest that you eliminate grapefruit juice from your diet.

Other verapamil interactions

The potential interactions with verapamil do not stop with prescriptions and foods. Aspects of your lifestyle and health conditions could also negatively impact therapy with verapamil.

Verapamil and alcohol

Verapamil can reduce the metabolism of alcohol, leading to higher levels and more profound and prolonged intoxication. You should check with your healthcare team to see if you should avoid alcohol altogether.

Verapamil and caffeine

Caffeine does not directly impact verapamil levels or vice versa. However, caffeine can speed up our heart rate, which directly opposes verapamil’s intent to control heart rate for some patients. Work with your doctor to determine how strictly to limit caffeine.

Verapamil and cannabis

Because cannabinoids like tetrahydrocannabinol (THC) are metabolized by the enzyme CYP3A4, drugs like verapamil that inhibit the enzyme can lead to heightened effects from cannabis. The interaction can magnify the adverse effects of cannabis, such as sedation, dizziness, and cognitive impairment.

Verapamil and congestive heart failure

In forms of congestive heart failure (CHF) associated with weakness of the heart’s main pumping chamber, so-called left ventricular dysfunction, verapamil can worsen outcomes, according to the American Heart Association. Careful consideration by your cardiologist is needed before using any medication in this situation.

Verapamil and Wolff-Parkinson-White (WPW) syndrome

A syndrome typified by dangerous rhythm problems of the heart, Wollf-Parkinson-White (WPW) syndrome can be negatively impacted by verapamil. Life-threatening ventricular fibrillation could be triggered by the drug in patients with WPW syndrome, so avoid the use of this calcium channel blocker.

Verapamil and neuromuscular disease

How our nervous system signals our muscles could be affected by verapamil. This effect is most important for those with neuromuscular diseases, like muscular dystrophy or myasthenia gravis. If you have a neuromuscular disease, discuss this concern with your neurologist to see if verapamil is safe to use and whether it needs to be modified.

Verapamil and pregnancy or breastfeeding

Verapamil is not contraindicated during pregnancy or breastfeeding. However, there are potential risks, which must be weighed against the benefits on a case-by-case basis.

How to minimize verapamil interactions

Early recognition or identification of a potential interaction, before it occurs is your best safety measure. Now that you know more about hazards, you can ask your healthcare providers and pharmacists more questions. To make the conversations more productive, you should compile a list of all your prescription drugs, over-the-counter medications, and dietary supplements, such as St. John’s Wort as it can affect how verapamil works. Do the same for your health conditions by listing them as well. Keep these records updated, and share them with your healthcare team regularly.

When to talk to a healthcare provider about verapamil interactions

The first time verapamil is to be prescribed to you, ask the prescriber and your pharmacist, “Does it interact with any of my other medications or health conditions?” You now have some background knowledge to understand the importance of the topic, but you need these professionals to help guide you. This article is for informational purposes and may not include drug information for every interaction. If you are already taking verapamil, it is not too late to ask, and in fact, you should ask the question every time a new medication is added in case it could interact with verapamil. By making these inquiries, you can be your own best healthcare advocate