Trade Names: Cymbalta
Drug Class: Antidepressant, serotononin/norepinephrine reuptake inhibitor (SNRI)
Preparations: 20-, 30-, 60 mg capsules
Dose: Fibromyalgia and chronic musculoskeletal pain: 30 mg once daily for a week then increase to 60 mg once daily if tolerated. Doses of 120 mg/day in clinical trials did not offer additional benefit (but increased side effects).
Depression: Initially 40-60 mg daily either as a single dose or in divided doses; usual maintenance 60 mg daily
Indications: Fibromyalgia, chronic musculoskeletal pain, major depression, anxiety disorder, diabetic neuropathy
Mechanism of Action: Increases synaptic concentrations of serotonin and norepinephrine
Contraindications: Hypersensitivity. Avoid for at least 14 days after patient has received an MAOI. Avoid in patients with uncontrolled narrow-angle glaucoma.
Precautions: May increase suicidality, particularly in adolescents. Risk of serotonin syndrome. Seizures reported. Avoid with hepatic disease or severe renal impairment. Caution with hypertension, seizures, gastroparesis. If discontinuing, reduce dose gradually over weeks or months to prevent withdrawal symptoms. Can exacerbate prostatism. Discontinue if any signs suggestive of Stevens Johnson syndrome.
Pregnancy Risk: C
Common: Nausea, constipation, headache, fatigue, dry mouth, dizziness, palpitations, insomnia, difficulty with urination, dry mouth, weight loss
Less common: Hypertension, mild increase in LFTs, orthostatic hypotension, withdrawal syndrome with abrupt discontinuation (nausea, vomiting, diarrhea, anxiety, dizziness, sleep disturbances), erectile dysfunction, worsen glucose control in diabetes
Rarely: Severe skin reactions, fractures, inappropriate ADH and hyponatremia, increased bleeding, fulminant hepatitis, serotonin syndrome, mania
Alcohol: Increased risk of elevated LFTs
MAOIs and serotonergic drugs: Risk of serotonin syndrome with concomitant use with other serotonergic drugs including triptans, tricyclic antidepressants, fentanyl, lithium,tramadol, tryptophan, buspirone and St. John’s Wort, and with drugs that impair metabolism of serotonin such as MAOIs and linezolid and methylene blue.
Catecholamines: Increased risk of arrhythmia and hypertension
Clonidine: May attenuate antihypertensive effect
CYP1A2 inhibitors: Strong inhibitors (e.g., ciprofloxacin, fluvoxamine, enoxacin) increase duloxetine levels many fold and should be avoided.
CYP2D6 inhibitors: Strong inhibitors (e.g., bupropion, paroxetine, fluoxetine, quinidine) increase duloxetine levels.
CYP2D6 substrates: Duloxetine inhibits CYP2D6 and can increase levels of CYP2D6 substrates (e.g., many antipsychotics and antidepressants, metoprolol, dextromethorphan and others).
Patient Instructions: Avoid alcohol use. Increased risk of suicide; contact physician for suicidal thoughts or change in behavior. Patients should be advised of the risk factors for serotonin syndrome and symptoms that may include mental changes (e.g., agitation, hallucinations, delirium), increased heart rate and labile blood pressure, dizziness, sweating, flushing, fever, tremor, rigidity, nausea, vomiting, diarrhea. Monitor blood pressure. Slow taper for discontinuation to prevent withdrawal symptoms.
Comments: Modestly more effective than placebo in fibromyalgia clinical trials; withdrawal for adverse effects was more common with duloxetine than placebo in fibromyalgia (19.6% vs. 11.8%) and OA (16.3% vs. 5.6%).
Clinical Pharmacology: Well absorbed, hepatic metabolism by CYP1A2 and CYP2D6, half-life 12 hours
Adapted from: RheumaKnowledgy