Herbs & Supplements

What interactions should I watch for?

Prescription Drugs

Studies have revealed that melatonin may interfere with the blood pressure-lowering effects of nifedipine GITS (Procardia XL). As a result, blood pressure was not controlled. Another medication used for blood pressure, verapamil (Calan, Isoptin, Verelan), reduced the effectiveness of melatonin when they were taken at the same time. Whether melatonin and other high blood pressure medicines interact is not known. Individuals who take medicine for high blood pressure should talk to a doctor or pharmacist before taking melatonin.

Fluvoxamine is an antidepressant that is known to increase natural melatonin production. It may also increase blood levels of melatonin if it is taken at the same time as melatonin supplements. If fluvoxamine and melatonin are taken together, the risk for side effects of melatonin may be increased. Other antidepressant medications may also interact with melatonin. Individuals who take an antidepressant should not take melatonin.

Some preliminary evidence suggests that melatonin can decrease some of the side effects, such as damage to the heart, kidneys, and liver, that may be caused by the immunosuppressant drug, cyclosporine (Neoral, Sandimmune). However, because it can enhance immune system function, melatonin may interfere with the effects of drugs used to suppress the immune system after organ transplants or in other conditions. Taking melatonin is not recommended for patients who take cyclosporine and related drugs such as:

• azathioprine (Imuran)
• CellCept
• corticosteroids
• Prograf
• Rapamune
• Zenapak

Melatonin opposes the action of natural corticosteroids and corticosteroid drugs, which are used for a wide range of inflammatory conditions including arthritis, asthma, cancer, eye conditions, and skin infections. When supplemental melatonin is taken at the same time as a corticosteroid drug, the effects of the corticosteroid may be decreased. It is best not to take melatonin and corticosteroids at the same time. Commonly prescribed corticosteroids include:

• beclomethasone (Beconase, Vancenase)
• dexamethasone (Decadron)
• hydrocortisone
• methylprednisolone (Medrol)
• prednisolone
• prednisone
• triamcinolone (Azmacort, Nasacort)

When melatonin is used with prescription drugs that promote sleepiness, the effects of the drug may be exaggerated, resulting in sedation or mental impairment. Prescription drugs that may cause sleepiness include:

• Anticonvulsants such as carbamazepine, phenytoin, and valproic acid (Depakote)
• Barbiturates such as phenobarbital
• Benzodiazepines such as alprazolam and diazepam (Valium)
• Drugs for insomnia such as Sonata and zolpidem
• Tricyclic antidepressants such as amitriptyline, amoxapine, doxepin and nortriptyline

In animal studies, melatonin has increased the anti-seizure effects of the anticonvulsant drugs, carbamazepine (Tegretol) and phenytoin (Dilantin).

Non-prescription Drugs

The sleep-producing effects of over-the-counter products containing diphenhydramine or doxylamine can be enhanced by taking melatonin at the same time. Diphenhydramine and doxylamine are contained in many over-the-counter sleep aids as well as in some cough and cold products, therefore caution should be used when taking these medications with melatonin because excessive drowsiness may result.

Herbal Products

Melatonin may cause excessive sedation if taken with sedating herbs such as:

• Catnip
• Hops
• Kava
• St. John's Wort
• Valerian

Foods

In several small studies of humans, caffeine has been shown to reduce the amounts of melatonin that the body produces naturally and also to block supplemental melatonin.

No other interactions between melatonin and foods have been reported, but drinking alcohol at the same time as taking melatonin may result in increased drowsiness.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how melatonin interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.