Drug Interaction Report

Spiramycin and Levodopa Oral Inhalation: Interaction Details

A pharmacist-reviewed analysis of the Spiramycin and Levodopa Oral Inhalation interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Levodopa Oral Inhalation

Inbrija Inbrija®
+

Spiramycin

No brand names on record
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
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.

Of 17 documented Spiramycin interactions, 2 are rated moderate — including this one.
Onset
delayed
Evidence
probable
Severity
Moderate

What happens

Reduced levodopa plasma concentrations and potential loss of antiparkinsonian effects

Interaction Deep Dive

Reduced levodopa area under the concentration-time curve (AUC) during concomitant administration of levodopa/carbidopa and spiramycin has been reported. Relative bioavailability of levodopa after a three-day course of spiramycin was 43% of levodopa bioavailability alone12.

Why it happens (mechanism)

Increased GI motility resulting in reduced bioavailability of carbidopa

Literature reports

1 report — tap to read

a) In a study using seven healthy male volunteers, a tablet containing levodopa 250 mg and carbidopa 25 mg (Sinemet(R) 250) was administered before and after a three-day course of spiramycin 1 gram twice a day 1. The area under the concentration-time curve (AUC) of levodopa fell significantly from 254 to 110 ng-min/mL. The AUC of the metabolite 3-O-methyldopa decreased from 272 to 134 ng-min/mL. The AUC of the metabolite dihydroxyphenylacetic acid (dopac) increased from 41 to 77 ng-min/mL. Carbidopa AUC decreased significantly from 28 to 1 ng-min/mL. The authors suggest that the clinical impact of these pharmacokinetic changes would be a loss of antiparkinsonian effects. The postulated mechanism was reduced absorption of carbidopa secondary to increased gastric motility induced by spiramycin. Alternatively, spiramycin therapy may have inactivated carbidopa by complex formation or increased presystemic metabolism.

Common questions

Can I take Spiramycin and Levodopa Oral Inhalation together?

Reduced levodopa plasma concentrations and potential loss of antiparkinsonian effects Always confirm with your pharmacist or prescriber before making any change.

How serious is the Spiramycin and Levodopa Oral Inhalation 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Spiramycin or Levodopa Oral Inhalation 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 (2)

  1. Brion N, Kollenbach K, Marion MH, et al: Effect of a macrolide (spiramycin) on the pharmacokinetics of L-dopa and carbidopa in healthy volunteers. Clin Neuropharmacol 1992; 15:229-235. PubMed
  2. von Rosenstiel NA & Adam D: Macrolide antibacterials. Drug interactions of clinical significance. Drug Saf 1995; 13(2):105-122. DOI
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Levodopa Oral Inhalation

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