S21 Pill — WHITE OVAL, 16mm — Penicillin V
| Imprint | S21 |
|---|---|
| Colour | WHITE |
| Shape | OVAL |
| Size | 16 |
| Strength | PENICILLIN V POTASSIUM 500 mg |
| Dosage form | Tablet |
| Manufacturer | Northwind Pharmaceuticals |
| NDC | 51655-011 |
| Schedule | — |
| Availability | — |
| Ingredients | PENICILLIN V POTASSIUM[PENICILLIN V] |
What does this imprint mean?
The imprint "S21" 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
Penicillin V
Uses and warnings
No boxed warning. Contraindicated in patients with "a previous hypersensitivity reaction to any penicillin." The label warns that "serious and occasionally fatal hypersensitivity (anaphylactic) reactions" have occurred, particularly in individuals with a history of penicillin or cephalosporin sensitivity, and notes the risk of Clostridioides difficile-associated diarrhea with virtually any antibacterial agent. It is not recommended for the treatment of severe pneumonia, bacteremia, meningitis, pericarditis, or other infections requiring high serum antibiotic levels.
Indicated for "mild to moderately severe infections due to penicillin G-sensitive microorganisms," including streptococcal infections of the upper respiratory tract, pneumococcal respiratory tract infections, mild staphylococcal skin and soft-tissue infections, and fusospirochetosis (Vincent's infection) of the oropharynx. Also used for prophylaxis against bacterial endocarditis in certain dental/surgical settings and for prevention of recurrence of rheumatic fever.
How to identify this pill
- • Check the imprint matches exactly: "S21".
- • Confirm the colour (WHITE) and shape (OVAL).
- • Compare the size (16) 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 8eee627c-3fd8-415e-ab52-61eb50b9b091.xml