Effexor and Pristiq: A Comparison of SNRI Antidepressants by Wyeth

Effexor and Effexor XR, the brand names of venlafaxine, are two of the most popular antidepressants on the market today. Their manufacturer, Wyeth Pharmaceuticals, has recently released Pristiq, the brand name of desvenlafaxine. The similarities in generic names is no coincidence: Effexor and Pristiq are essentially the same drug. Desvenlafaxine is the active metabolite of venlafaxine. What this means is that venlafaxine turns into desvenlafaxine after it's been metabolized by the body. Effexor was introduced in 1993 and Effexor XR, the extended release formula, was released shortly thereafter. Pristiq was introduced in late 2008. I'll compare the medications on ten different points, and it will be up to you and your doctor to decide which one might be right for you.

Mechanism of Action: Both are Serotonin and Norepinephrine Reuptake Inhibitors, medications that go one step further than the Selective Serotonin Reuptake Inhibitors like Prozac and Zoloft. By inhibiting the reuptake of both serotonin and norepinephrine, key neurotransmitters believed to influence mood, they are supposed to be more effective. Or at least that's the theory since no one really knows why these drugs actually work.

Treatment Indications: Wyeth's website reports that Effexor and Effexor XR have been FDA approved to treat major depressive disorder, generalized anxiety disorder, panic disorder and social anxiety disorder. As of the publishing of this article, Pristiq has only been approved to treat major depressive disorder.

Cost: Effexor and Effexor XR are available as generics. This dramatically decreases their cost, which is especially important for patients with no prescription drug coverage. Pristiq is not available as a generic, and won't be for many years.

Long-term Efficacy: Drugs.com reports that clinical trials have demonstrated Effexor's efficacy as a long-term treatment. A 26 week placebo-controlled trial showed that patients with recurrent depression not only responded to Effexor, but they continued to improve during the course of the study. These same patients were then followed for up to 52 weeks in a second placebo-controlled study and Effexor was still providing relief. Wyeth reports that Pristiq's efficacy has been demonstrated in four 8 week placebo-controlled trials. No one knows how effective it is in the long term.

Side Effects, Part 1: Both Effexor and Pristiq can cause serotonin syndrome, especially if either is taken with other antidepressants and certain migraine medications. Serotonin syndrome results from too much serotonin in the brain is potentially fatal if not treated according to the National Institute of Health's Medline Plus Medical Encyclopedia.

Side Effects, Part 2: Wyeth reports that another serious side effect of Effexor and Pristiq is sustained hypertension, especially at higher doses. They recommend that patients have their blood pressure checked regularly. Other less serious side effects include weight gain (Effexor but not Pristiq), nausea, dizziness, vomiting, constipation and insomnia. Abnormal bleeding, like nose bleeds and bruising, can occur especially if the patient is taking aspirin, NSAIDs like ibuprofen and blood thinners.

Initiating Treatment: Effexor must be slowly titrated up to its therapeutic dose over several weeks. Pristiq can be started at the initial recommended therapeutic dose of 50 milligrams.

Discontinuing Treatment: Effexor is infamous for its severe discontinuation symptoms (aka withdrawal). Similar withdrawal symptoms are being reported by patients taking Pristiq. Patients have experienced these symptoms even if dose is taken a few hours late. Abrupt discontinuation can cause such serious symptoms as muscle spasms, dizziness and impaired coordination, hypomania, agitation, confusion and seizures according to Drugs.com. Wyeth recommends slowly decreasing the dosage if either drug is to be discontinued, but there still may be withdrawal symptoms.

Use In Pregnancy: Effexor and Pristiq are listed as Pregnancy Category C, which means that they have not been studied well in humans but animal studies have shown adverse effects on the fetus. They can be used if the benefits outweigh the risks, so they're not totally contraindicated. Newborns who were exposed to Effexor, especially during the third trimester, are at a higher risk of developing difficulty breathing, seizures, feeding difficulties, and low blood sugar, among other serious symptoms. According to Drugs.com, these newborns are more likely to require prolonged hospitalization, feeding tubes and respiratory support such as supplemental oxygen. One can assume that Pristiq would cause similar problems in newborns since it is so similar to Effexor, but no one knows for sure right now.

Use While Breastfeeding: Effexor is compatible with breastfeeding. According to Dr. Thomas Hale, PhD., the leading authority on medications and breastfeeding, it is reasonably safe for the breastfeeding mother and infant. Pristiq is so new that no one really knows for sure, but Dr. Hale suggests "it's probably OK to breastfeed" while taking Pristiq."

Each medication has its benefits and drawbacks, but with the introduction of Pristiq, doctors and patients now have another viable option for treating depression and anxiety disorders.

Sources:
Wyeth Pharmaceuticals, "Effexor XR: A Depression and Anxiety Disorders Treatment." Effexor XR.
Wyeth Pharmaceuticals, "Pristiq is a prescription medication approved for the treatment of depression." Pristiq.
Drugs.com, "Effexor Official FDA information, side effects and uses." Drugs.com.
Drugs.com, "Pristiq Information from Drugs.com." Drugs.com.
United States National Library of Medicine, "MedlinePlus Medical Encyclopedia: Serotonin Syndrome." MedlinePlus.
Dr. Thomas Hale, PhD., "Dr. Hale's Breastfeeding and Medications Forum > Topics." Texas Tech University Health Sciences Center School of Medicine at Amarillo.