penicillin G potassium

Action

Inhibits biosynthesis of cell-wall mucopeptide; bactericidal against penicillin-susceptible microorganisms during active multiplication stage

Availability

Powder for injection: 1 million, 5 million, and 20 million units/vial Premixed (frozen) solution for injection: 1 million, 2 million, and 3 million units/50 ml

Indications and dosages

➣ Meningococcal meningitis

Adults: 1 to 2 million units I.M. q 2 hours or 20 to 30 million units/day by continuous I.V. infusion for 14 days, or until afebrile for 7 days

➣ Meningitis caused by susceptible pneumococcal or meningococcal strains

Children: 250,000 units/kg/day in equally divided doses I.M. or by continuous I.V infusion q 4 hours for 7 to 14 days (depending on causative organism)

Infants older than 7 days: 200,000 to 300,000 units/kg/day I.V. in divided doses q 6 hours

Infants less than 7 days old: 100,000 to 150,000 units/kg/day I.V. in divided doses q 12 hours

➣ Actinomycosis

Adults: 1 to 6 million units/day I.M. or I.V. for cervicofacial infections; 10 to 20 million units/day I.V. q 4 to 6 hours for 6 weeks for thoracic and abdominal infections

➣ Clostridial infections

Adults: 20 million units/day I.M. or I.V. infusion q 4 to 6 hours, given with antitoxin therapy

➣ Fusospirochetal infections

Adults: 5 to 10 million units/day I.M. or 200,000 to 500,000 units I.V. infusion q 4 to 6 hours

➣ Rat bite fever; Haverhill fever

Adults: 12 to 20 million units/day I.M. or I.V. infusion q 4 to 6 hours for 3 or 4 weeks

➣ Pasteurella infections

Adults: 4 to 6 million units/day I.M. or I.V. infusion q 4 to 6 hours for 2 weeks

➣ Erysipeloid endocarditis

Adults: 12 to 20 million units/day I.M. or I.V. infusion q 4 to 6 hours for 4 to 6 weeks

➣ Diphtheria (as adjunctive therapy with antitoxin to prevent carrier state)

Adults: 2 to 3 million units/day I.M. or I.V. infusion in divided doses q 4 to 6 hours for 10 to 12 days

➣ Anthrax

Adults: At least 5 million units/day I.M. or I.V. infusion

➣ Serious streptococcal infections

Adults: 5 to 24 million units/day I.M. or I.V. infusion in divided doses q 4 to 6 hours

➣ Neurosyphilis

Adults: 18 to 24 million units/day I.V. (given in doses of 3 to 4 million units q 4 hours) for 10 to 14 days

➣ Listeria infections

Adults: 15 to 20 million units/day I.M. or I.V. infusion q 4 to 6 hours for 2 weeks in meningitis or 4 weeks in endocarditis

➣ Disseminated gonococcal infections

Adults: 10 million units/day I.V. (3 to 4 million units q 4 hours) for 10 to 14 days

Off-label uses

• Lyme disease

• Predental prophylaxis against bacterial endocarditis

Contraindications

• Hypersensitivity to penicillins or beta-lactamase inhibitors (piperacillin/tazobactam)

Precautions

Use cautiously in:

• severe renal insufficiency, significant allergies, asthma

• pregnant or breastfeeding patients.

Administration

• Before giving, ask patient about allergy to penicillin, beta-lactamase inhibitors, or benzathine. Know that cross-sensitivity to imipenem and cephalosporins also may occur.

See Keep epinephrine and emergency equipment at hand in case anaphylaxis occurs.

• For I.V. use, dilute in sterile water for injection, normal saline solution, or dextrose 5% in water (D₅W). For continuous infusion, further dilute in 1 to 2 L of compatible solution and infuse over 24 hours. For intermittent infusion, further dilute in 50 or 100 ml of normal saline solution or D₅W; administer over 1 to 2 hours in adults or 15 to 30 minutes in children and infants.

• Know that drug also may be given by intrapleural or intrathecal route.

• Be aware that in syphilis treatment, Jarisch-Hersheimer reaction (fever, chills, headache, sweating, malaise, hypotension or hypertension) may occur 2 to 12 hours after therapy starts and usually subsides within 24 hours.

Adverse reactions

CNS: hyperreflexia, neuropathy, coma, seizures

CV: arrhythmias, cardiac arrest, heart failure (with high I.V. doses)

GI: nausea, vomiting, diarrhea, epigastric distress, abdominal pain, colitis, blood in stool, glossitis, pseudomembranous colitis

GU: nephropathy

Hematologic: hemolytic anemia, leukopenia, thrombocytopenia Metabolic: hyperkalemia (with high-dose, continuous I.V. infusion)

Skin: rash, urticaria, exfoliative dermatitis

Other: pain at I.M. injection site, phlebitis at I.V. site, Jarisch-Hersheimer reaction, superinfection, anaphylaxis, serum sickness

Interactions

Drug-drug. Aspirin, probenecid: increased penicillin blood level

Erythromycins, tetracyclines: decreased antimicrobial activity of penicillin

Hormonal contraceptives: decreased contraceptive efficacy

Drug-diagnostic tests. Alanine aminotransferase, eosinophils, granulocytes, hemoglobin, platelets, potassium, white

blood cells: increased levels

Direct Coombs' test: positive result Sodium: decreased level

Urine glucose, urine protein: false-positive results

Patient monitoring

See Watch closely for signs and symptoms of anaphylaxis and serum sickness.

• In long-term therapy, monitor electrolyte levels and CBC with white cell differential; watch for electrolyte imbalances and blood dyscrasias.

• Closely monitor neurologic status, especially for seizures and decreasing level of consciousness.

See Stay alert for signs and symptoms of superinfection and pseudomembranous colitis.

Patient teaching

See Teach patient to recognize signs and symptoms of anaphylaxis. Tell him to contact emergency medical services immediately if these occur.

See Tell patient drug may cause diarrhea. Instruct him to immediately report severe, persistent diarrhea and fever.

• Urge patient to complete entire course of therapy as prescribed, even after symptoms improve.

• Tell patient to contact prescriber if infection symptoms worsen.

• Inform female patient that drug may make hormonal contraceptives ineffective. Advise her to use barrier birth-control method if she wishes to avoid pregnancy.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.