Drug Interactions:
SSRIs

Since the development of Prozac, the first of the selective serotonin-reuptake inhibitors (SSRIs), this family of drugs has been expanding. The SSRIs are used for both severe and mild to moderate depression as well as for a variety of other conditions. These drugs work primarily by increasing the activity of the neurotransmitter (chemical messenger) serotonin in the brain. SSRI antidepressants include

• citalopram (Celexa)
• fluoxetine (Prozac)
• fluvoxamine (Luvox)
• paroxetine (Paxil)
• sertraline (Zoloft)
• and others

Other antidepressants that increase serotonin activity include

• nefazodone (Serzone)
• trazodone (Desyrel)
• venlafaxine (Effexor)

5-HTP (5-Hydroxytryptophan), SAMe (S-Adenosylmethionine)

Possible Harmful Interaction

The body uses the natural substance 5-hydroxytryptophan (5-HTP) to manufacture serotonin, and supplemental forms have been used for treating depression and migraine headaches.

S-adenosylmethionine (SAMe) is a naturally occurring compound derived from the amino acid methionine and the energy molecule adenosine triphosphate (ATP). SAMe is widely used as a supplement for treating osteoarthritis and depression.

Based on one case report and current thinking about how they work, SAMe and 5-HTP should not be taken with SSRIs, as they might increase the risk of serotonin syndrome.

This syndrome is a toxic reaction brought on by too much serotonin activity. The condition requires immediate medical attention, with symptoms including anxiety, restlessness, confusion, weakness, tremor, muscle twitching or spasm, high fever, profuse sweating, and rapid heartbeat.

The report describes a case of apparent serotonin syndrome in an individual taking SAMe with clomipramine, a tricyclic antidepressant that increases serotonin activity.¹

Although SAMe is not currently known to affect serotonin, it does appear to have antidepressant effects and may in some way increase serotonin activity.

Because SSRIs increase serotonin activity even more than clomipramine, a similar problem might occur if you combine SAMe with an SSRI.

The supplement 5-HTP is used by the body to manufacture serotonin, so it could also increase the risk of serotonin syndrome when combined with an SSRI.

St. John's Wort

Possible Harmful Interaction

The herb St. John's wort (Hypericum perforatum) is primarily used to treat mild to moderate depression. One of its actions appears to be increasing the activity of serotonin in the brain.

If you are taking an SSRI medication, do not take the herb St. John's wort at the same time. It is possible that your serotonin levels might be raised too high, causing a dangerous condition called serotonin syndrome^2,3 (please see previous topic).

Several case reports appear to bear this out. Serotonin syndrome was reported in five elderly individuals who began using St. John's wort while taking sertraline (four reports) or nefazodone (one report).⁴ One individual had symptoms resembling serotonin syndrome after combining paroxetine (50 mg daily) and St. John's wort (600 mg daily).⁵ Another person taking St. John's wort with two other serotonin-enhancing drugs was reported to experience serotonin syndrome.⁶

Furthermore, if you wish to switch from an SSRI to St. John's wort, you may need to wait a few weeks for the SSRI to wash out of your system before it is safe to start taking the herb. The waiting time required depends on which SSRI you are taking. Ask your physician or pharmacist for advice.

Folate

Supplementation Possibly Helpful

Folate is a B vitamin that offers many important health benefits. Not only does it help prevent birth defects and possibly reduce the risk of heart disease, a recent study suggests that folate can also help SSRI antidepressants work better.

In this double-blind placebo-controlled trial, 127 individuals with severe depression were given either Prozac plus folate (500 mcg daily) or Prozac alone.¹⁰ Researchers wanted to see whether the vitamin would increase the medication's effectiveness.

The results were different for men and women. Female participants definitely benefited from receiving folate along with the medication. While just under 50% of the women taking Prozac alone fully recovered from their depression, combination treatment produced a recovery rate of nearly 75%. This is a very marked difference, and one that makes a strong case for combining folate with antidepressant therapy.

Men, however, did not do any better on combination treatment than on Prozac alone. Researchers found evidence that a higher dose would have been necessary for male participants, perhaps 800 to 1,000 mcg daily. However, for dosages this high, medical supervision is necessary.

Ginkgo

Supplementation Possibly Helpful

The herb ginkgo (Ginkgo biloba) has been used to treat Alzheimer's disease and ordinary age-related memory loss, among many other uses.

SSRIs can cause many sexual side effects, including inability to achieve orgasm (in women) and impotence (in men). Ginkgo appears to help reverse these problems.

This particular benefit of ginkgo is one of those interesting chance discoveries. An elderly man who was experiencing SSRI-related sexual dysfunction⁷ began taking Ginkgo biloba for its purported enhancement of memory. After 4 weeks on the herb, he was surprised and pleased to report that his sexual function had improved. When he tried stopping the herb, the problems resurfaced; on restarting it, the prior benefits returned.

This prompted his physician to investigate ginkgo further. Evidence from preliminary studies now suggests that ginkgo can help both men and women with sexual difficulties caused by SSRIs.^8,9

Though double-blind studies are needed to confirm these findings, the preliminary results are impressive enough to consider a trial of ginkgo if you are experiencing this problem. As there are some potential safety issues with ginkgo, check with your physician first.

Last reviewed March 2002 by Medical Review Board

Back to Top