Taking tizanidine with other drugs that make you sleepy or slow your breathing can cause dangerous side effects or death. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.
Tell your doctor about all your other medicines, especially:
-
- acyclovir;
- ticlopidine;
- zileuton;
- birth control pills;
- an antibiotic – ciprofloxacin, levofloxacin, moxifloxacin, or ofloxacin;
- blood pressure medicine – clonidine, guanfacine, methyldopa;
- heart rhythm medicine – amiodarone, mexiletine, propafenone, verapamil; or
- stomach acid medicine – cimetidine, famotidine.
Zanaflex (tizanidine) has several important drug interactions, primarily due to its hepatic metabolism via the CYP1A2 enzyme, as well as its central nervous system (CNS) depressant effects. Below is a detailed breakdown:
🔶 Major Interactions
1. CYP1A2 Inhibitors
These drugs increase tizanidine levels, potentially leading to excessive sedation, low blood pressure, and bradycardia.
| Drug Class | Examples | Resulting Risk |
|---|---|---|
| Fluoroquinolones | Ciprofloxacin (⚠️ contraindicated) | Profound hypotension, sedation |
| Macrolides | Erythromycin | Increased tizanidine levels |
| Antidepressants | Fluvoxamine (⚠️ contraindicated) | Dangerous CNS depression |
| Oral contraceptives | Ethinyl estradiol combinations | May increase tizanidine exposure |
| Cimetidine | (H2 blocker) | Potentiates effects |
🔶 CNS Depressants
Concurrent use enhances sedation, dizziness, fatigue, and risk of falls or respiratory depression.
| Drug Type | Examples |
|---|---|
| Benzodiazepines | Diazepam, Lorazepam |
| Opioids | Oxycodone, Hydrocodone |
| Alcohol | — |
| Antipsychotics | Quetiapine, Olanzapine |
| Sleep aids | Zolpidem, Eszopiclone |
| Antihistamines | Diphenhydramine, Hydroxyzine |
🔶 Antihypertensives
Zanaflex can lower blood pressure. When combined with other antihypertensives, it may cause hypotension or fainting.
| Type | Examples |
|---|---|
| Beta blockers | Metoprolol, Propranolol |
| ACE inhibitors | Lisinopril, Enalapril |
| Calcium channel blockers | Amlodipine, Diltiazem |
🔶 Herbal & OTC Interactions
| Substance | Effect |
|---|---|
| Valerian root | Increased CNS depression |
| St. John’s Wort | May reduce tizanidine effectiveness (induces CYP1A2) |
| Kava, melatonin | Additive sedation |
🔶 Food Interaction
- Food increases tizanidine absorption, but unpredictably:
- With food: higher and prolonged blood levels
- Without food: lower levels
- Consistency is key: always take with or without food the same way every time
🔶 Contraindicated Combinations
- Ciprofloxacin + Tizanidine
- Fluvoxamine + Tizanidine
These combinations are contraindicated due to extreme hypotension, bradycardia, and excessive sedation.
Summary Table
| Interaction Type | Clinical Concern | Action Required |
|---|---|---|
| CYP1A2 Inhibitors | ↑ Tizanidine → Toxicity | Avoid or use alternative |
| CNS Depressants | Additive sedation, respiratory risk | Monitor or avoid |
| Antihypertensives | Enhanced BP drop | Dose adjustment, monitor closely |
| Food | Alters absorption | Take consistently with or without |
| Herbal Sedatives | Additive CNS depression | Avoid combination |
Let me know if you want a printable table or a drug-specific risk analysis (e.g., ciprofloxacin + tizanidine).