duloxetine

Mechanism

Additive seizure threshold reduction plus elevated synaptic norepinephrine (bupropion is a norepinephrine-dopamine reuptake inhibitor; duloxetine is an SNRI). Tachycardia and hypertension may emerge.

Symptoms

Tachycardia, hypertension, tremor, agitation. Seizures may occur, especially with prior epilepsy or eating disorders.

Management

The combination is possible for antidepressant augmentation with careful blood pressure and pulse monitoring. Cap bupropion at 300 mg and duloxetine at 60 mg/day. Avoid with prior epilepsy or eating disorders.

Mechanism

Ciprofloxacin is a potent CYP1A2 inhibitor, the main duloxetine metabolic route. Duloxetine plasma levels rise 6-fold. Nausea, sedation, and serotonergic effects emerge.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

Avoid the combination. Alternative antibiotics without CYP1A2 effect: a cephalosporin, nitrofurantoin, or fosfomycin. If ciprofloxacin is needed, halve the duloxetine dose.

Mechanism

SSRI + SNRI – serotonergic load rises, serotonin syndrome risk. Duloxetine also prolongs QT at high doses, summing with citalopram's QT effect.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. When switching antidepressants, allow a 2-week washout. Alternative monotherapy: mirtazapine or agomelatine.

Mechanism

SSRI + SNRI – serotonergic load rises, serotonin syndrome risk. The combination has no therapeutic rationale.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. When switching antidepressants, allow a 1-week washout. For augmentation, use mirtazapine or agomelatine.

Mechanism

Fluoxetine is a potent CYP2D6 inhibitor; duloxetine is minorly metabolised by CYP2D6. Additive serotonergic load with dual SSRI/SNRI dosing.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. When switching from fluoxetine to duloxetine, allow a 5-week washout (due to norfluoxetine); from duloxetine to fluoxetine, 1 week.

Mechanism

Dual risk. Fluvoxamine is a potent CYP1A2 inhibitor, the main duloxetine metabolic route. Duloxetine plasma levels rise 6-fold. Plus additive serotonergic load.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. Choose one antidepressant: duloxetine for pain syndromes, fluvoxamine for obsessive-compulsive disorder. For augmentation, add mirtazapine.

Mechanism

Linezolid is a reversible monoamine oxidase (MAO) inhibitor. Duloxetine (SNRI) raises synaptic serotonin and norepinephrine. Co-administration: serotonin syndrome (FDA safety alert 2011, fatal cases reported).

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. Stop duloxetine at least 5 days before starting linezolid. For urgent antibiotic therapy: vancomycin, daptomycin, or ceftaroline by susceptibility.

Mechanism

Mirtazapine + SNRI – augmentation in resistant depression ('California rocket fuel'). Serotonin syndrome is rare but possible at high doses.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is possible for augmentation. Keep doses low: mirtazapine 15–30 mg, duloxetine 30–60 mg/day. Monitor blood pressure, pulse, and mental status in the early weeks.

Mechanism

SSRI (sertraline) + SNRI (duloxetine) – additive serotonergic load, serotonin syndrome risk without therapeutic rationale.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. When switching antidepressants, allow a 1-week washout. For augmentation, use mirtazapine or agomelatine.

Mechanism

Dual risk. Duloxetine (SNRI) raises synaptic serotonin and norepinephrine. Tramadol blocks serotonin and norepinephrine reuptake and lowers seizure threshold. Combined action amplifies serotonergic activity.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

Avoid the combination. For analgesia on duloxetine, use paracetamol, an NSAID, or morphine/oxycodone. For neuropathic pain, gabapentin or pregabalin.

Mechanism

Dual SNRI – doubling the same pharmacological effect without therapeutic benefit. Risk of serotonin syndrome, hypertension, and tachycardia.

Symptoms

Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.

Management

The combination is not prescribed. Choose one: venlafaxine for depression or generalised anxiety disorder, duloxetine for pain syndromes (diabetic neuropathy, fibromyalgia). When switching, allow a 1-week washout.

Mechanism

Duloxetine is a serotonin-norepinephrine reuptake inhibitor (SNRI). It depletes the platelet serotonin pool, impairing primary haemostasis. On warfarin, upper GI bleeding risk roughly doubles.

Symptoms

Gum bleeding, epistaxis, bruising without trauma, blood in urine or stool, menorrhagia. Severe cases include gastrointestinal or intracranial haemorrhage. Risk rises in patients over 65 and with prior peptic ulcer disease.

Management

The combination is acceptable. PPI cover with pantoprazole is mandatory. Check INR at 2 and 4 weeks after starting duloxetine, then monthly. Alternative antidepressants with minimal platelet effect: mirtazapine or agomelatine.