Methyldopa and Pseudoephedrine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Methyldopa
Pseudoephedrine
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
Loss of blood pressure control and possibly hypertensive urgency
Interaction Deep Dive
Coadministered pseudoephedrine may alter the antihypertensive effect of methyldopa and could produce a loss of blood pressure control and an increase in the risk of hypertensive episodes132.
Why it happens (mechanism)
Unknown
Literature reports
2 reports — tap to read
a) Ten hypertensive patients ranging in age from 33 to 62 were given methyldopa 0.75 to 2 grams daily for 4 to 10 days 1. Study subjects were administered a single intravenous injection of noradrenaline (1 to 8 mcg). In some of the patients, the pressor effect of noradrenaline was increased in magnitude after they had received methyldopa. More striking was the marked prolongation of action of the noradrenaline seen in every case during concomitant methyldopa administration.
b) A severe hypertensive reaction was reported in a patient who was well-controlled on methyldopa and oxprenolol. The reaction occurred two days after the patient began therapy with a cold preparation containing phenylpropanolamine and acetaminophen 2.
Common questions
Can I take Methyldopa and Pseudoephedrine together?
Loss of blood pressure control and possibly hypertensive urgency Always confirm with your pharmacist or prescriber before making any change.
How serious is the Methyldopa and Pseudoephedrine interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
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 Methyldopa or Pseudoephedrine 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 (3)
- Dollery CT, Harington M, & Hodge JV: Haemodynamic studies with methyldopa: effect on cardiac output and response to pressor amines. Br Heart J 1963; 25:670. DOI
- McLaren EH: Severe hypertension produced by interaction of phenylpropanolamine with methyldopa and oxprenolol. Br Med J 1976; 2:283-284. DOI
- Sneddon JM & Turner P: Ephedrine mydriasis in hypertension and the response to treatment. Clin Pharmacol Ther 1969; 10:64. PubMed
Keep reading about Methyldopa
Keep reading about Pseudoephedrine
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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