penicillin V potassium
Brand: Pen VK, Veetids
Prototype: penicillin-g
Drug Class: antibiotic (penicillin)
Drug Family: antibiotic
Subclass: natural penicillin
Organ Systems: infectious-disease
Mechanism of Action
Binds and irreversibly inhibits transpeptidase (PBP), blocking the final cross-linking step of peptidoglycan synthesis in the bacterial cell wall. The resulting cell wall defects cause osmotic lysis. Active primarily against gram-positive organisms. Acid-stable (unlike penicillin G), allowing oral administration.
penicillin-binding proteins (PBPs)transpeptidase
Indications
- pharyngitis (streptococcal, Group A)
- mild community-acquired pneumonia (streptococcal)
- prophylaxis for rheumatic fever recurrence
- mild skin and soft tissue infections
Contraindications
- severe penicillin allergy (anaphylaxis)
Adverse Effects
Common
- nausea
- diarrhea
- rash
Serious
- anaphylaxis
- severe skin reactions
- C. difficile colitis
- hemolytic anemia (rare)
Pharmacokinetics (ADME)
| Absorption | oral; bioavailability ~60-73%; food reduces absorption (take on empty stomach for best levels) |
| Distribution | protein binding ~80%; does not penetrate CSF well |
| Metabolism | minimal hepatic; hydrolysis to penicilloic acid (inactive) |
| Excretion | renal tubular secretion; CrCl adjustment required in severe impairment |
| Half-life | 0.5-1 hour |
| Onset | 30-60 minutes |
| Peak | 0.5-1 hour |
| Duration | 6 hours |
| Protein Binding | 80% |
| Vd | 0.2-0.35 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| probenecid | blocks renal tubular secretion; increases and prolongs penicillin levels | moderate |
| methotrexate | penicillins reduce renal methotrexate clearance; toxicity risk | major |
Nursing Considerations
- Take on empty stomach 1 hour before or 2 hours after meals for maximal absorption.
- For streptococcal pharyngitis, the full 10-day course must be completed even if symptoms resolve to prevent rheumatic fever.
- Screen for penicillin allergy before administration; inquire specifically about anaphylaxis, urticaria, or rash to differentiate IgE-mediated from non-IgE reactions.
- For rheumatic fever prophylaxis, patients may take penicillin V daily for years; adherence counseling is essential.
Clinical Pearls
- Penicillin V is the preferred antibiotic for streptococcal pharyngitis; despite 70 years of use, Group A Streptococcus has not developed resistance to penicillin.
- The cross-reactivity between penicillin allergy and cephalosporin allergy is approximately 1-2% (not 10% as historically taught); most penicillin-allergic patients can safely receive cephalosporins.
Safety Profile
Pregnancy safe
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.