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Drugs, Supplies and Delivery
Duloxetine (Cymbalta)
Duloxetine, marketed under the brand name Cymbalta (not Lustral¹), is a serotonin-norepinephrine reuptake inhibitor (SNRI) used to treat major depressive disorder (MDD), generalized anxiety disorder (GAD), and chronic pain conditions such as diabetic peripheral neuropathy and fibromyalgia. Known for its dual mechanism of action, duloxetine is effective but requires careful management due to its side effect profile. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of duloxetine, including its mechanism, uses, dosing, side effects, precautions, interactions, and availability.
Duloxetine inhibits the reuptake of serotonin (5-HT) and norepinephrine (NE) at presynaptic neurons, increasing their availability in the synaptic cleft. This dual action enhances mood regulation and pain modulation:
- Serotonin: Improves mood and reduces anxiety.
- Norepinephrine: Enhances arousal and pain relief (Lippincott Textbook of Pharmacology).
Duloxetine also has mild effects on dopamine reuptake, contributing to its efficacy in chronic pain conditions (Lange Basic & Clinical Pharmacology).
- Major Depressive Disorder (MDD):
- First-line treatment for acute episodes and maintenance therapy (BNF).
- Generalized Anxiety Disorder (GAD):
- Reduces excessive worry and physical symptoms.
- Diabetic Peripheral Neuropathy:
- Alleviates neuropathic pain in diabetes.
- Fibromyalgia:
- Improves pain, fatigue, and quality of life.
- Chronic Musculoskeletal Pain:
- Effective in managing osteoarthritis and chronic lower back pain (Lange Basic & Clinical Pharmacology).
- Adults:
- Initial Dose: 30 mg once daily, preferably in the morning or evening.
- Maintenance Dose: 60 mg once daily; maximum 120 mg/day (BNF).
- Elderly or Hepatically Impaired Patients:
- Start with 30 mg/day and titrate cautiously (Lippincott).
Administration:
- Take with or without food.
- Swallow capsules whole; do not crush or chew (Lange Basic & Clinical Pharmacology).
- Common: Nausea, dry mouth, headache, insomnia, and fatigue (BNF).
- Serious:
- Hypertension: Dose-dependent increase in blood pressure (monitor regularly).
- Serotonin Syndrome: Agitation, hyperthermia, and tachycardia (rare but life-threatening).
- Hepatotoxicity: Elevated liver enzymes; avoid in severe hepatic impairment (Lippincott).
- Withdrawal Symptoms: Dizziness, irritability, and "brain zaps" if abruptly discontinued (Lange Basic & Clinical Pharmacology).
- Contraindications:
- Concurrent use of MAO inhibitors (risk of serotonin syndrome).
- Uncontrolled narrow-angle glaucoma (BNF).
- Monitoring:
- Blood pressure at baseline and during dose escalation.
- Liver function tests in patients with hepatic impairment (Lippincott).
- Pregnancy/Lactation:
- BNF Category C: Use only if benefits outweigh risks; potential neonatal withdrawal.
- Excreted in breast milk—consult a specialist (Lange Basic & Clinical Pharmacology).
- MAO Inhibitors: Risk of serotonin syndrome; allow a 14-day washout period (BNF).
- Other Serotonergic Drugs (e.g., tramadol, triptans): Increased serotonin syndrome risk.
- CYP1A2 Inhibitors (e.g., fluvoxamine): Raise duloxetine levels; monitor for toxicity.
NSAIDs/Anticoagulants: Elevated bleeding risk due to platelet inhibition (Lippincott).
Duloxetine is the generic name. Brand names include Cymbalta® and Yentreve®. Generic formulations are widely available as:
- Capsules: 20 mg, 30 mg, 60 mg.
- Delayed-Release Capsules: 30 mg, 60 mg (BNF).
