Primidone and Nimodipine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Primidone
Nimodipine
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.
What happens
Decreased nimodipine effectiveness
Interaction Deep Dive
A single dose study has shown that concurrent use of enzyme inducing antiepileptic agents (phenytoin, phenobarbital, and carbamazepine) with nimodipine has resulted in decreased nimodipine levels1. Although not reported for primidone, similar results would be expected.
Why it happens (mechanism)
Increased nimodipine metabolism
Literature reports
1 report — tap to read
a) Three groups of eight subjects were studied 1. Group 1 was comprised of healthy subjects, group 2 had epileptic patients treated at least four months with carbamazepine, phenobarbital, phenytoin (all enzyme inducers), or a combination, and group 3 included patients with epilepsy treated for at least four months with sodium valproate. Compared to the control group, nimodipine AUCs averaged a 7-fold decrease in the enzyme inducer group, probably due to induction of first-pass metabolism. The nimodipine AUCs were increased by 50% in the valproate-treated group.
Common questions
Can I take Primidone and Nimodipine together?
Decreased nimodipine effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Primidone and Nimodipine interaction?
It is rated minor. Usually limited clinical impact.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Primidone or Nimodipine 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 anything you'd monitor while I'm on both?
References (1)
- Tartara A, Galimberti CA, Manni R, et al: Differential effects of valproic acid and enzyme-inducing anticonvulsants on nimodipine pharmacokinetics in epileptic patients. Br J Clin Pharmacol 1991; 32:335-340. PubMed
Keep reading about Primidone
Keep reading about Nimodipine
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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