Antibiotic — Tonsillitis / Pharyngitis

Phenoxymethylpenicillin (Penicillin V)

Brand names: Penicillin VK

Phenoxymethylpenicillin (penicillin V) is a narrow-spectrum oral penicillin used for streptococcal infections such as tonsillitis, and for prophylaxis (e.g. asplenia, rheumatic fever).

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

DOSAGE AND ADMINISTRATION The dosage of Penicillin V should be determined according to the sensitivity of the causative microorganisms and the severity of infection, and adjusted to the clinical response of the patient. The usual dosage recommendations for adults and children 12 years and over are as follows: Streptococcal Infections Mild to moderately severe - of the upper respiratory tract and including scarlet fever and erysipelas: 125 to 250 mg (200,000 to 400,000 units) every 6 to 8 hours for 10 days. Pneumococcal Infections Mild to moderately severe - of the respiratory tract, including otitis media: 250 to 500 mg (400,000 to 800,000 units) every 6 hours until the patient has been …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2025-10-15. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

A beta-lactam that inhibits bacterial cell-wall synthesis.

Prescribing in practice

Contraindicated in penicillin allergy.
Take it on an empty stomach (before food) for better absorption.
For sore throat, target antibiotics using clinical scores (e.g. FeverPAIN/Centor) per guidance.

Monitoring

Short courses need no routine monitoring.

Counselling the patient

Take it before food and complete the course.
Report a rash or other signs of allergy.

Evidence & guidelines

First-line for group A streptococcal throat infection and certain prophylaxis indications per NICE/PHE guidance.

Reference: NICE NG84 (Sore Throat — Antibiotic Prescribing 2018); SIGN 117; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways