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Does Promethazine Phenylephrine Codeine Interact with Erythromycin?

Promethazine Phenylephrine Codeine and Erythromycin have a major drug interaction according to U.S. FDA drug labeling data. CYP3A4 inhibitor may increase codeine plasma concentrations and morphine levels, potentially causing fatal respiratory depression. The mechanism involves cyp3a4 inhibition leading to increased codeine/morphine metabolism. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.

Severity
Major
Erythromycin Class
Macrolide
Management
Close medical supervision required
Data Source
U.S. FDA via OpenFDA

How This Interaction Works

The interaction between Promethazine Phenylephrine Codeine and Erythromycin occurs because cyp3a4 inhibition leading to increased codeine/morphine metabolism. Clinically, this means cyp3a4 inhibitor may increase codeine plasma concentrations and morphine levels, potentially causing fatal respiratory depression. This is classified as a major interaction, meaning it could cause serious harm if not properly managed. Your healthcare provider may need to adjust dosages, substitute one medication, or increase monitoring frequency.

What To Tell Your Doctor or Pharmacist

If you are taking Promethazine Phenylephrine Codeine and your doctor is considering prescribing Erythromycin (or vice versa), make sure to:

  • Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
  • Ask whether the benefits of combining these medications outweigh the risks for your specific situation
  • Ask what symptoms to watch for that would indicate the interaction is causing problems
  • Ask how frequently you should be monitored while these are co-prescribed
  • Ask whether any dosage adjustments are needed
  • Never stop or change either medication without first consulting your healthcare provider
💊 Promethazine Phenylephrine Codeine(Promethazine And Phenylephrine Hcl, And Codeine Phosphate)+💊 Erythromycin

Severity & Interaction Details

⚠️
major
Use with caution — major interaction
Serious risk of clinically significant harm. Generally avoid; if used, monitor closely.
Severity scale
MinorContra
On record
Yes
Drug A class
—
Drug B class
Macrolide
Source
NLP:promethazine, phenylephrine, codeine

What this means in plain English

CYP3A4 inhibitor may increase codeine plasma concentrations and morphine levels, potentially causing fatal respiratory depression.

What the FDA label says

"CYP3A4 inhibition leading to increased codeine/morphine metabolism"

📖 Source: NLP:promethazine, phenylephrine, codeine

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Data sourced from U.S. FDA drug labeling via openFDA and the NIH National Library of Medicine. For informational purposes only. Always consult your pharmacist or physician.