The FDA has issued yet another warning about drug interactions with antidepressants that raise serotonin levels, and in particular the SSRI and SNRI antidepressants. (See list below)

The new FDA warnings are about interactions with the antibacterial drug Zyvox (linezolid), one of the few antibiotics left that is still effective against infections such as MRSA and drug-resistant pneumonias and staph infections. (Although Zyvox is supposed be used sparingly, as a last resort, so that bugs don’t build resistance to it, in 2008 it was one of the top 15 best-selling anti-infective drugs in the world.) According to the FDA, there are increasing reports of patients suffering from serotonin syndrome when they are taking antidepressants that increase serotonin levels and then are given Zyvox. Serotonin syndrome is a potentially life-threatening drug reaction to excess serotonin in the brain. Although the list below includes typical serotonin syndrome symptoms, reports of the Zyvox drug interactions also included seizures, delirium and coma.

Serotonin Syndrome Symptoms

• Agitation or restlessness
• Diarrhea
• Fast heart beat
• Hallucinations
• Increased body temperature
• Loss of coordination
• Nausea
• Overactive reflexes
• Rapid changes in blood pressure
• Vomiting

Source: PubMed Health

The bottom line is that patients who are currently taking serotonergic drugs should not be given Zyvox unless it’s a life-threatening emergency.

Other SSRI Drug Interactions and Warnings

Even without these new warnings, Prozac for example, has interactions with 779 other drugs, 201 of them considered to be “major” which translates as dangerous. Other drugs in the SSRI and SNRI family have similarly long lists of drug interactions.

SSRIs increase the risk of osteoporosis, reduce sex drive considerably and cause sleep disturbances, just to name a few of the more serious side effects.

Many SSRI and SNRI antidepressants have a black box warning that reads, “Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants for major depressive disorder (MDD) and other psychiatric disorders.” A black box is the strongest warning the FDA can issue without pulling the drug off the market.

Serotonin-raising antidepressants are also increasingly found to increase the risk of birth defects and developmental delays in children whose mothers took the drugs while pregnant.

The majority of recent research on SSRIs shows that for mild to moderate depression they have about the same efficacy as a placebo (sugar pill).

Examples of SSRI and SNRI Antidepressants

Fluoxetine (e.g. Prozac, Sarafem)

Paroxetine (e.g. Paxil, Aropax, Seroxat, Sereupin)

Sertraline  (e.g. Zoloft, Lustral)

Escitalopram oxalate (e.g. Lexapro, Cipralex, Seroplex, Lexamil, Lexam)

Citalopram  (e.g. Celexa, Cipramil)

Fluvoxamine (e.g. Luvox)

Venlafaxine (e.g. Effexor or Efexor)

Duloxetine (e.g. Cymbalta)

SSRIs and Methylene Blue

The new FDA warnings also apply to a chemical called methylene blue, used rarely in medicine to treat cyanide poisoning and in some diagnostic procedures. Methylene blue is also put in aquariums to treat fungal infections in tropical fish, and as such should not come in contact with the skin.

Zyvox and Wellbutrin, Zyban

The FDA warning for serotonin syndrome reactions also applies to the drug bupropion (Wellbutrin, Zyban) and other antidepressants. This FDA Drug Safety Communication gives a detailed list of antidepressants that can interact with Zyvox.

More Information and References

Pedersen LH, Henriksen TB, Olsen J, “Fetal exposure to antidepressants and normal milestone development at 6 and 19 months of age,” Pediatrics. 2010 Mar;125(3):e600-8. Epub 2010 Feb 22.

Sie SD, Wennink JM, van Driel JJ et al, “Maternal use of SSRIs, SNRIs and NaSSAs: practical recommendations during pregnancy and lactation,” Arch Dis Child Fetal Neonatal Ed. 2011 Jul 27.

Top-Sellng Antimicrobials Worldwide: http://knol.google.com/k/global-antiviral-antibiotics-market-review-2008-world-top-ten-antimicrobial#Table_1%282E%29_World_Top_15_Anti%282D%29Infective_Drugs_in_2008

Prozac Drug Interactions: http://www.drugs.com/drug-interactions/fluoxetine,prozac.html

  fda antidepressant warning, fda drug warning, ssris drug interactions