Methyldopa and Lithium Carbonate: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Methyldopa
Lithium Carbonate
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
An increased risk of toxic side effects
Interaction Deep Dive
Concomitant use of lithium and methyldopa may increase the risk of toxic side effects1. Several case reports have demonstrated that concurrent administration of methyldopa with lithium has resulted in signs of lithium toxicity 423.
Why it happens (mechanism)
Unknown
Literature reports
3 reports — tap to read
a) A 42-year-old female on lithium carbonate therapy with therapeutic levels of lithium was treated for hypertension with methyldopa and developed swollen feet, ataxia, shakiness, slurred speech, and vocal soreness. Following discontinuation of both drugs, the patient's serum lithium dropped from 1.5 to 0.1 mEq/L within nine days and she showed no signs of tremor or ataxia, although slurred speech persisted 2.
b) A 45-year-old woman who was receiving lithium carbonate 900 mg daily for five years, was generally well controlled. The patient then began to show initial signs of manic decompensation and was admitted to the hospital where it was learned that she had been diagnosed as having hypertension. The patient was discharged on a regimen of 1800 mg of lithium carbonate and 1 g of methyldopa daily with serum levels of lithium below 1 mEq/L. Despite the therapeutic level of lithium, the patient began to show signs of lithium toxicity manifested by diarrhea, hand tremor, blurred vision, slurring speech and confusion. Methyldopa was discontinued and lithium was decreased to 1500 mg daily. The patient's serum lithium level was 1.4 mEq 10 days later. Lithium was reduced to 900 mg daily with a subsequent serum lithium level of 1 mEq/L 3.
c) Concomitant administration of lithium and methyldopa was reported to result in elevations of lithium serum levels and lithium toxicity in a 69-year-old woman. The interaction may occur secondary to methyldopa-induced sodium retention, resulting in reabsorption of lithium ions 4.
Common questions
Can I take Methyldopa and Lithium Carbonate together?
An increased risk of toxic side effects Always confirm with your pharmacist or prescriber before making any change.
How serious is the Methyldopa and Lithium Carbonate interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Methyldopa or Lithium Carbonate 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 (4)
- Product Information: LITHOBID(R) oral extended-release tablets, lithium carbonate oral extended-release tablets. ANI Pharmaceuticals Inc (per DailyMed), Baudette, MN, 2018. DailyMed
- O'Regan JB: Adverse interaction of lithium carbonate and methyldopa. Can Med Assoc J 1976; 115:385.
- Byrd GJ: Methyldopa and lithium carbonate - suspected interaction. JAMA 1975; 233:320. DOI
- Yassa R: Lithium-methyldopa interaction. Can Med Assoc J 1986; 134:141-142.
Keep reading about Methyldopa
Keep reading about Lithium Carbonate
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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