Amitriptyline and Primidone: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amitriptyline
Primidone
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
These two medicines can affect each other in a few ways. Primidone (Mysoline) is used mostly for seizures, and it speeds up how your body breaks down amitriptyline (Elavil). That can lower the amount of amitriptyline in your blood, so it may not work as well for your mood or nerve pain.
There are two other things to know. Amitriptyline can make seizures a little easier to trigger, which matters if you take primidone for epilepsy. And because both drugs can make you sleepy and slow your breathing, together they can cause extra drowsiness. The good news: your care team can manage this by adjusting your doses and watching how you feel.
Effect: Reduced TCA exposure plus additive CNS/respiratory depression. Neither agent requires bioactivation here; amitriptyline is active as given.
- Mechanism: Primidone (and its barbiturate metabolite phenobarbital) induces hepatic enzymes, increasing amitriptyline metabolism and lowering serum TCA levels.
- Direction: Reduced amitriptyline efficacy; scattered reports of decreased TCA serum concentrations.
- Additional risks: TCAs lower seizure threshold (may worsen seizure control); additive sedation and respiratory depression.
- Onset: Delayed. Evidence: Probable. Severity: Major.
- Management: Monitor mood/analgesic response and TCA levels; watch seizure frequency and sedation; individualize dosing.
What happens
Reduced tricyclic antidepressant exposure and possible additive adverse effects
Interaction Deep Dive
Using barbiturates together with tricyclic antidepressants (TCAs) can enhance the metabolism of the TCA. Isolated reports describe patients whose serum TCA concentrations fell when a barbiturate was also present 123. TCAs may additionally impair seizure control because they lower the seizure threshold. Beyond this, the two agents produce additive depression of both the CNS and respiration 4.
Why it happens (mechanism)
Increased tricyclic antidepressant metabolism
How to manage this interaction
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your care team can manage this combination.
- Your amitriptyline dose may need to be adjusted and individualized because primidone can lower its levels and effect.
- Your team may monitor you more closely, watching how well your depression or pain is controlled and whether your seizures stay controlled.
- Tell your prescriber if you feel unusually drowsy, dizzy, or short of breath, since both drugs can add to sedation.
- Ask your pharmacist before adding other sedating medicines or alcohol.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) The pharmacokinetics of a single 100 mg oral dose of desipramine were examined in eight patients with epilepsy receiving long-term PHENobarbital treatment and in eight drug-free healthy controls. Every subject was classified as an extensive metabolizer for the genetically determined CYP2D6-related metabolic polymorphism. In comparison with the controls, the epilepsy patients showed lower peak plasma desipramine concentrations (74 nmol/L vs. 107 nmol/L), smaller desipramine area under the concentration-time curve values (1943 nmol/L/h vs. 3234 nmol/L/h), and shorter desipramine elimination half-lives (15.1 h vs. 20.6 h). All barbiturates are thought to produce comparable effects that induce hepatic enzymes, and the 2D6 isozyme is considered important in the metabolism of most or all TCAs. Consequently, similar effects should be anticipated with any combination of a TCA and a barbiturate 5.
Common questions
Can I take Amitriptyline and Primidone together?
Primidone can lower amitriptyline levels (reducing its effect), amitriptyline can lower the seizure threshold, and together they add to drowsiness, so your care team may adjust doses and monitor you more closely. Keep taking both as prescribed and report excess sedation or breathing changes. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Primidone interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Amitriptyline and Primidone interaction managed?
Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your care team can manage this combination. Your amitriptyline dose may need to be adjusted and individualized because primidone can lower its levels and effect. Your team may monitor you more closely, watching how well your depression or pain is controlled and whether your seizures stay controlled. Tell your prescr… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Amitriptyline or Primidone need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (5)
- Moody JP, Whyte SF, MacDonald AJ, et al: Pharmacokinetic aspects of protriptyline plasma levels. Eur J Clin Pharmacol 1977; 11:51-56. PubMed
- Silverman G & Braithwaite R: Interaction of benzodiazepines with tricyclic antidepressants (letter). Br Med J 1972; 4:111. PubMed
- Burrows GD & Davies B: Antidepressants and barbiturates. Br Med J 1971; 4:113. PubMed
- Brodie MJ: Drug interactions in epilepsy. Epilepsia 1992; 33(suppl 1):S13-S22. PubMed
- Spina E, Avenoso A, Campo GM, et al: Phenobarbital induces the 2-hydroxylation of desipramine. Ther Drug Monit 1996; 18:60-64. DOI
Keep reading about Amitriptyline
Keep reading about Primidone
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