Should clomipramine, atomoxetine (Strattera), and mirtazapine (Remeron) be used together?

Combining Clomipramine, Strattera (Atomoxetine), and Remeron (Mirtazapine): High-Risk Combination

This three-drug combination carries significant risk for serotonin syndrome and should be avoided or used only with extreme caution under close monitoring. All three medications have serotonergic activity, and combining multiple serotonergic agents substantially increases the risk of potentially fatal serotonin syndrome 1.

Primary Safety Concern: Serotonin Syndrome

The combination of clomipramine (a tricyclic antidepressant with strong serotonergic properties), atomoxetine (a norepinephrine reuptake inhibitor with some serotonergic effects), and mirtazapine (an atypical antidepressant affecting serotonin) creates a dangerous accumulation of serotonergic activity.

Serotonin syndrome presents with:

• Mental status changes (confusion, agitation, anxiety)
• Neuromuscular hyperactivity (tremors, clonus, hyperreflexia, muscle rigidity)
• Autonomic hyperactivity (hypertension, tachycardia, arrhythmias, tachypnea, diaphoresis, shivering, vomiting, diarrhea)
• Advanced symptoms include fever, seizures, arrhythmias, and unconsciousness leading to death 1

Symptoms typically arise within 24-48 hours after combining medications and require hospital-based treatment with discontinuation of all serotonergic agents and continuous cardiac monitoring 1.

Guideline Recommendations on Combining Serotonergic Drugs

Caution is explicitly required when combining two or more non-MAOI serotonergic drugs, including TCAs (like clomipramine) and atypical antidepressants (like mirtazapine) 1. The guidelines state that when a second serotonergic drug must be added, it should be:

• Started at a low dose
• Increased slowly
• Monitored closely for symptoms, especially in the first 24-48 hours after dosage changes 1

Additional Drug Interaction Concerns

Atomoxetine (Strattera) has specific warnings about combining with other medications affecting monoamine concentrations. The FDA label explicitly warns of serious, sometimes fatal reactions (including hyperthermia, rigidity, myoclonus, autonomic instability, and mental status changes progressing to delirium and coma) when combined with drugs affecting brain monoamine concentrations 2.

Limited Evidence for Multi-Antidepressant Combinations

There is limited evidence supporting the use of two antidepressants as an initial treatment approach or specific endpoint 3. While medication combinations may be justified to treat multiple disorders in the same patient, evidence supporting combinations based on covering multiple neurotransmitter systems is rudimentary at best 3.

Research on mirtazapine combinations shows:

• Combining mirtazapine with SSRIs/SNRIs did not demonstrate clinically important benefits in treatment-resistant depression 4
• Combination therapy with mirtazapine and other antidepressants can alter pharmacokinetics and requires caution 5
• While some case series show promise, controlled evidence is lacking 6, 7

Clinical Decision Algorithm

If this combination is already prescribed:

1. Immediately assess for any signs of serotonin syndrome
2. Monitor vital signs and mental status closely
3. Educate patient/family about warning signs requiring emergency care
4. Consider tapering to reduce polypharmacy risk

If considering this combination:

1. First, question the necessity - Is there a clear rationale for each medication?
2. Consider alternatives - Can the clinical goals be achieved with fewer serotonergic agents?
3. If proceeding despite risks:
   • Start with the lowest possible doses
   • Add medications sequentially, not simultaneously
   • Monitor intensively for 24-48 hours after each dose change
   • Obtain informed consent documenting the off-label, high-risk nature
   • Schedule frequent follow-up visits (weekly initially)

Common Pitfalls to Avoid

• Never assume safety because the patient has tolerated the combination previously - serotonin syndrome can occur at any time, especially with dose increases
• Don't dismiss mild symptoms - early signs like restlessness, tremor, or diaphoresis may herald more serious toxicity
• Avoid adding a third serotonergic agent to treat side effects of the first two (e.g., adding another medication for anxiety that develops)
• Don't rely on "covering neurotransmitter bases" as justification - this approach lacks evidence and increases risk 3

The safest approach is to avoid this three-drug combination entirely and pursue alternative treatment strategies with fewer serotonergic agents.