Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: duloxetine

BRAND NAME: Cymbalta

DRUG CLASS AND MECHANISM: Duloxetine is a selective serotonin and norepinephrine reuptake inhibitor (SSNRI). It increases the amounts of serotonin and norepinephrine in the brain that help maintain mental balance and stop the movement of pain signals in the brain. As an anti–depressant, it shares its mechanism with venlafaxine (Effexor). Both of these medicines are related to the selective serotonin and norepinephrine reuptake inhibitor (SSRIs) – fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), citalopram (Celexa), and escitalopram (Lexapro). Similar to venlafaxine and the SSRIs, duloxetine is also effective in managing generalized anxiety disorder. Additionally, duloxetine has pain–reducing activity and has been used in the treatment of neuropathic pain associated with diabetic peripheral neuropathy. The mechanism responsible for its effectiveness in this pain state is not known, but is thought to involve its effects on serotonin and norepinephrine in the brain. Duloxetine was approved by the FDA in August 2004.

GENERIC: no

PRESCRIPTION: yes

PREPARATIONS: Delayed–release capsules: 20mg, 30mg, 60mg

STORAGE: Capsules should be stored at room temperature, between 15 and 30°C (59–86°F).

PRESCRIBED FOR: Duloxetine is used for the treatment of depression, generalized anxiety disorder, and neuropathic pain associated with diabetic peripheral neuropathy.

DOSING: Most patients can be started with a 60mg dose taken once daily with or without food. Some doctors prefer to begin some patients with a 30mg dose, taken once daily, and then increase the dose to 60mg once daily after one week. There is no evidence that doses greater than 60 mg/day provide additional benefits.

DRUG INTERACTIONS: Duloxetine should not be used in combination with a monoamine oxidase inhibitor (MAOI) – phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), selegiline (Eldepryl) – or within at least 14 days of discontinuing the MAOI. At least 5 days should be allowed after stopping duloxetine before starting an MAOI. Combinations of SSRIs and MAOIs have led to serious, sometimes fatal, reactions including very high body temperature, rigidity, rapid fluctuations of heart rate and blood pressure, extreme agitation progressing to delirium and coma.

The use of duloxetine with other medicines that can increase the amount of serotonin the body may result in "serotonin syndrome." Serotonin syndrome symptoms may include agitation, hallucinations, coma, increased heart rate, changes in blood pressure, high body temperature, incoordination, nausea, vomiting, and diarrhea. Such medicines include MAOIs, the triptan class of anti–migraine medicines [e.g. sumatriptan (Imitrex)], as well as clomipramine (Anafranil), trazodone (Desyrel), tricyclic antidepressants such as amitriptyline (Elavil).

PREGNANCY: In animal studies, duloxetine has been shown to have adverse effects on fetal development. There are no adequate studies in pregnant women. Duloxetine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

NURSING MOTHERS: Duloxetine is excreted into the milk of lactating women. Because the safety of duloxetine in infants is not known, nursing while on duloxetine is not recommended.

SIDE EFFECTS: The most common side effects noted with duloxetine are nausea (experienced by about 1 to 2 of every 5 patients), dry mouth (1 of 6), constipation (1 of 9), diarrhea (1 of 10), fatigue (1 of 10), difficulty sleeping (1 of 9), dizziness (1 of 10). Between two and four times as many people who received duloxetine during clinical studies had to stop treatment and drop out of the study due to side effects than those receiving placebo.

Antidepressants may increase the risk of suicidal thinking and behavior in children and adolescents with depression. Patients who are started on duloxetine or another antidepressant should be observed closely for clinical worsening, suicidal thinking and behavior, or unusual behavior. The average risk of suicidal thinking and behavior in patients receiving antidepressants is about 4% (or 1 per 25), twice the placebo risk of 2%.

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