Flecainide and Nirmatrelvir/Ritonavir Interaction
Drug interaction information between Flecainide and Nirmatrelvir/Ritonavir.
Flecainide and Nirmatrelvir/Ritonavir have a documented major interaction in FDA labeling.
FDA drug labeling documents a major-severity interaction between Flecainide and Nirmatrelvir/Ritonavir. This page displays the available source-record category and label text. The category is not an individual risk estimate or medication-combination direction.
How They Interact
Ritonavir blocks the enzymes that process flecainide, leading to much higher levels of the heart drug in your system. This increase can cause the heart to beat in an unsafe or irregular way.
FDA Label Information
Antiarrhythmics amiodarone, dronedarone, flecainide, propafenone, quinidine ↑ antiarrhythmic Co-administration contraindicated due to potential for cardiac arrhythmias [see Contraindications (4) ] .
Flecainide Also Interacts With
- Darifenacin moderate
- Fluoxetine moderate
- Propranolol minor
- Diltiazem minor
- Nifedipine minor
Nirmatrelvir/Ritonavir Also Interacts With
- Simvastatin major
- Lovastatin major
- Sildenafil major
- Carbamazepine major
- Rifampin major
Frequently Asked Questions
What SPL severity band is on file for Flecainide + Nirmatrelvir/Ritonavir?
Compiled FDA labeling labels this pair major. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Nirmatrelvir/Ritonavir has 86 labeled pairs on file vs Flecainide's 22. In the major band specifically: Flecainide has 1; Nirmatrelvir/Ritonavir has 23 (also Simvastatin, Lovastatin, Sildenafil, Carbamazepine).
What mechanism field is on file for Flecainide and Nirmatrelvir/Ritonavir?
Ritonavir blocks the enzymes that process flecainide, leading to much higher levels of the heart drug in your system. This increase can cause the heart to beat in an unsafe or irregular way.
Nirmatrelvir/Ritonavir carries more major-labeled pairs than Flecainide
SPL source-record counts only. This page's band is major · classes on file: Flecainide (Class IC Antiarrhythmic); Nirmatrelvir/Ritonavir (Antiviral (Protease Inhibitor Combination)).
Nirmatrelvir/Ritonavir has 23 major-labeled pairs vs Flecainide's 1.
1 major · 2 moderate · 19 minor · 22 total
Flecainide has no other major-band peer in this dataset besides Nirmatrelvir/Ritonavir.
23 major · 30 moderate · 33 minor · 86 total
- Other major peers for Nirmatrelvir/Ritonavir
- Simvastatin
- Lovastatin
- Sildenafil
- Carbamazepine
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. This registry does not provide individual medication-combination directions.
Read our methodology - how this data is sourced, computed, and verified.