5-Hydroxytryptophan (5-HTP) - Possible Drug Interactions

5-HTP supplements haven't been tested for safety and keep in mind that the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established. You can get tips on using supplements, but if you're considering the use of 5-HTP, talk with your doctor first. Please note that this is only a partial list (please consult your doctor for a complete list).

 Some of the possible herb-drug interactions may include:

Carbidopa:

Carbidopa is used to control Parkinson's disease symptoms such as tremor, rigidity, and unsteady gait. In one report, carbidopa and 5-HTP taken together was believed to be responsible for the development of a scleroderma-like illness. Some studies have found that people taking carbidopa together with 5-HTP have ​also been found to improve a condition called intention myoclonus.

Dextromethorphan:

Dextromethorphan is a cough suppressant. No interactions have been reported, however, drugs that increase serotonin, such as serotonin reuptake inhibitors, have been reported to cause visual hallucinations and excess drowsiness when combined.

MAO inhibitor drugs:

e.g. Phenelzine®, Selegiline®, Tranylcypromine®
MAO inhibitors are used in the treatment of depression and panic disorder and in the prevention of headache. Although there have been no reported drug interactions with 5-HTP, MAO inhibitors may cause drowsiness, confusion, fever, agitation, seizures, elevated blood pressure, called serotonin syndrome.

A study by Hokkaido University found the risk of serotonin syndrome was lower with selegiline than other MAO inhibitors.

Selective Serotonin Reuptake Inhibitors (SSRIs):

e.g. Fluoxetine®, Fluvoxamine®, Sertraline®, Sibutramine®
Selective serotonin reuptake inhibitors are used for depression, premenstrual dysphoric syndrome, bulimia nervosa, obsessive-compulsive disorder, and weight loss.

5-HTP is converted to serotonin, so medications that increase serotonin may increase the risk of developing a rare but serious condition called serotonin syndrome symptoms include confusion, muscle rigidity, hot flashes, changes in blood pressure and heart rate, and coma.

Triptans:

e.g. Sumatriptan®, Zolmitriptan®, Rizatriptan®, Naratriptan®, Almotriptan®, Eletriptan®, Frovatriptan®
Triptan drugs are used to treat, but not prevent, migraines. These drug work by affecting serotonin receptors in the brain. If taken in combination with 5-HTP (a supplement that also affects serotonin levels), they may increase the risk of serotonin syndrome.

Tramadol:

Tramadol is an analgesic for moderate to severe pain. Although no drug interactions have been reported, 5-HTP may increase the effects of Tramadol, increasing the risk of seizures or serotonin syndrome.

Other antidepressants:

e.g. Venlafaxine®, Nefazodone®, Trazodone®
Other medications that affect the uptake of the neurotransmitter serotonin may lead to serotonin syndrome when used together with 5-HTP.

Zolpidem:

Zolpidem is used for the short-term relief of insomnia. Although drug interactions have not been reported with 5-HTP, Zolpidem together with drugs that affect serotonin levels were believed to cause visual hallucinations, slow breathing and speech, and poor coordination.

Sources
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Healthnotes. A-Z Guide to Drug-Herb-Vitamin Interactions. New York: Three Rivers Press, 2006.
Izumi T et al. "Effects of co-administration of a selective serotonin reuptake inhibitor and monoamine oxidase inhibitors on 5-HT-related behavior in rats." European Journal of Pharmacology. 532.3 (2006):258-64.
Navarro A wt al. "A case of serotonin syndrome precipitated by abuse of the anticough remedy dextromethorphan in a bipolar patient treated with fluoxetine and lithium." General Hospital Psychiatry. 28.1 (2006):78-80.
Rybacki, James J. The Essential Guide to Prescription Drugs 2006. New York: Collins, 2006.
Sternberg EM et al. "Development of a scleroderma-like illness during therapy with L-5-hydroxytryptophan and carbidopa." New England Journal of Medicine. 303.14 (1980):782-7.
Thal LJ et al. "Treatment of myoclonus with L-5-hydroxytryptophan and carbidopa: clinical, electrophysiological, and biochemical observations." Annals of Neurology. 7.6 (1980) :570-6.
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Van Woert MH et al. "Long-term therapy of myoclonus and other neurologic disorders with L-5-hydroxytryptophan and carbidopa." New England Journal of Medicine. 296.2 (1977):70-5.

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