Class: Penicillin Antibiotic
Dosage Forms. Tablet: 250 mg, 500 mg; Powder for Suspension: 125 mg/5 mL, 250 mg/5 mL; Powder for Solution: 125 mg/5 mL, 250 mg/5 mL
Common FDA Label Indication, Dosing, and Titration.
1. Bacterial endocarditis, prophylaxis in patients with congenital heart disease or rheumatic/acquired valvular heart disease: Adults, 2 g po 1 h prior to procedure and then 1 g po 6 h later; Children <60 pounds, 1 g po 1 h prior to procedure and then 500 mg po 6 h later
2. Otitis media, mild-moderate, pneumococcal: Adults, 250-500 mg po q6h until afebrile for at least 2 d; Children <12 y of age, 25-50 mg/kg/d po in 3-4 divided doses, max 3 g/d
3. Streptococcal pharyngitis: Adults, 500 mg po bid × 10 d; Children <60 pounds, 250 mg po bid
1. Pneumococcal infectious disease, prophylaxis in patients with sickle cell disease or asplenia: Children 2 mo to 5 y, 125 mg po bid; Children 5 y and older, 250 mg po bid; discontinue at age 5 y for children who received pneumococcal vaccination and who have not experienced invasive pneumococcal disease
MOA. Penicillins are active against most Gram-positive organisms and some Gram-negative organisms, notably Neisseria sp., by interfering with late stages of bacterial cell wall synthesis; resistance is caused primarily by bacterial production of β-lactamases; some organisms have altered penicillin-binding protein targets (eg, enterococci and pneumococci); others have impermeable outer cell wall layers.
Drug Characteristics: Penicillin
Medication Safety Issues: Penicillin
Drug Interactions: Penicillin
Adverse Reactions: Penicillin
Efficacy Monitoring Parameters. Resolution of clinical signs of infection.
Toxicity Monitoring Parameters. Seek care for severe diarrhea, dark urine, yellowing of skin or eyes, unusual bruising or bleeding, blistering skin rash, or shortness of breath.
Key Patient Counseling Points. Complete full course of therapy. For suspension, shake well and store in the refrigerator. Note short expiration after reconstitution (discard 2 wk after reconstitution). Avoid mixing suspension with food or beverages, but food can be taken afterward. Symptoms should improve within 2-3 d; if they worsen, seek care.
Clinical Pearls. There is cross hypersensitivity between penicillin and cephalosporins; use with caution in cephalosporin allergic. May resume normal activities after 24 h of antibiotics if afebrile. First antibiotic, produced in 1943, referred to as the “magic bullet.”