penicillin G potassium

penicillin G potassium

Pfizerpen

Pharmacologic class: Penicillin

Therapeutic class: Anti-infective

Pregnancy risk category B

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.
☞ 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.

Route	Onset	Peak	Duration
I.M.	Rapid	15-30 min	4-6 hr
I.V.	Rapid	End of infusion	4-6 hr

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

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

Patient teaching

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