Tizanidine and Acyclovir Interaction
Drug interaction information between Tizanidine and Acyclovir.
Tizanidine and Acyclovir have a documented minor interaction in FDA labeling.
FDA drug labeling documents a minor-severity interaction between Tizanidine and Acyclovir. 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
Acyclovir blocks a specific liver enzyme that breaks down tizanidine. This causes the muscle relaxant to stay in your body at much higher levels, which can be dangerous.
FDA Label Information
7.2 Moderate or Weak CYP1A2 Inhibitors Concomitant use of tizanidine with moderate or weak CYP1A2 inhibitors (e.g., zileuton, antiarrhythmics [amiodarone, mexiletine, propafenone, and verapamil], cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided.
Tizanidine Also Interacts With
- Ciprofloxacin major
- Fluvoxamine major
- Famotidine moderate
- Verapamil minor
- Amiodarone minor
Acyclovir Also Interacts With
- Bictegravir/Emtricitabine/Tenofovir minor
- Cidofovir minor
- Emtricitabine/Tenofovir minor
- Meperidine minor
- Tenofovir Disoproxil minor
Frequently Asked Questions
What SPL severity band is on file for Tizanidine + Acyclovir?
Compiled FDA labeling labels this pair minor. That is a source-record field, not an individual medication-combination decision.
Which drug in this pair has the larger labeled-interaction portfolio?
Tizanidine has 17 labeled pairs on file vs Acyclovir's 7. In the minor band specifically: Tizanidine has 14 (also Verapamil, Amiodarone, Propafenone, Mexiletine); Acyclovir has 7 (also Bictegravir, Cidofovir, Emtricitabine/Tenofovir, Meperidine).
What mechanism field is on file for Tizanidine and Acyclovir?
Acyclovir blocks a specific liver enzyme that breaks down tizanidine. This causes the muscle relaxant to stay in your body at much higher levels, which can be dangerous.
Tizanidine carries more major-labeled pairs than Acyclovir
SPL source-record counts only. This page's band is minor · classes on file: Tizanidine (Central Alpha-2 Agonist (Muscle Relaxant)); Acyclovir (Antiviral (Nucleoside Analog)).
Tizanidine has 2 major-labeled pairs vs Acyclovir's 0. This page itself is in the minor band, not the major band.
2 major · 1 moderate · 14 minor · 17 total
- Other minor peers for Tizanidine
- Verapamil
- Amiodarone
- Propafenone
- Mexiletine
0 major · 0 moderate · 7 minor · 7 total
- Other minor peers for Acyclovir
- Bictegravir
- Cidofovir
- Emtricitabine/Tenofovir
- Meperidine
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.