503 Pill — WHITE ROUND, 9mm — Tizanidine
| Imprint | 503 |
|---|---|
| Colour | WHITE |
| Shape | ROUND |
| Size | 9 |
| Strength | TIZANIDINE HYDROCHLORIDE 4 mg |
| Dosage form | Tablet |
| Manufacturer | Aphena Pharma Solutions - Tennessee, LLC |
| NDC | 71610-451 |
| Schedule | — |
| Availability | — |
| Ingredients | TIZANIDINE HYDROCHLORIDE[TIZANIDINE] |
What does this imprint mean?
The imprint "503" is a code stamped or printed on the tablet or capsule by the manufacturer, used to identify the drug, its strength and the maker.
Active ingredient
Tizanidine
Uses and warnings
No boxed warning. Key warnings include hypotension/bradycardia (blood pressure drops of ≥20% occurred in about two-thirds of patients, with risk of syncope), hepatotoxicity (roughly 5% of patients had liver enzyme elevations, with rare reports of fatal hepatic failure, requiring baseline and periodic LFT monitoring), marked sedation (reported by 48% of patients overall, and 92% at a single 16 mg dose), and hallucinations/psychotic-like symptoms (about 3% of patients). Contraindicated with concomitant fluvoxamine or ciprofloxacin (potent CYP1A2 inhibitors), which markedly increase tizanidine blood levels.
Tizanidine is indicated for "the management of spasticity." The label notes it is short-acting and should be reserved for the daily activities and times when relief of spasticity is most important, as its benefit is limited to the duration of drug action and not all patients respond.
How to identify this pill
- • Check the imprint matches exactly: "503".
- • Confirm the colour (WHITE) and shape (ROUND).
- • Compare the size (9) against a ruler if possible.
- • When in doubt, confirm with a pharmacist before taking any medication.
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Official references
Source: FDA Structured Product Label via NLM Pillbox archive (retired 2021); source file dd861284-8693-4273-bd3e-451c5c333fc2.xml