penicillin G benzathine
Bicillin L-A, Permapen
penicillin G benzathine and procaine
Bicillin C-R, Bicillin C-R 900/300
penicillin G potassium
Pfizerpen
penicillin G procaine
Bicillin C-R, Wycillin
penicillin G sodium
Therapeutic classification: antibiotic
Pregnancy risk category B
Available forms
Available by prescription only
penicillin G benzathine
Injection: 300,000 units/ml; 600,000 units/ml; 1.2 million units/2 ml; 2.4 million units/4 ml
Suspension: 250,000 units/5 ml ◆; 500,000 units/ml ◆
penicillin G benzathine and procaine
Injection: 300,000 units/ml, 600,000 units/ml, 1.2 million units/2 ml, 2.4 million units/4 ml containing equal volumes of penicillin
G benzathine and procaine; 1.2 million units/2 ml as 900,000 units penicillin G benzathine and 300,000 units penicillin G
procaine (Bicillin CR 900/300)
penicillin G potassium
Injection (premixed, frozen): 1 million units/50 ml, 2 million units/50 ml, 3 million units/50 ml
Powder for injection: 1 million units, 5 million units, 10 million units, 20 million units
penicillin G procaine
Injection: 600,000 units/ml; 1.2 million units/2 ml; 2.4 million units/4 ml
penicillin G sodium
Powder for injection: 1 million units ◆, 5 million units, 10 million units ◆, 20 million units
Indications and dosages 
Congenital syphilis. penicillin G benzathine.
Children younger than age 2: 50,000 units/kg I.M. as a single injection. Group A streptococcal upper respiratory infections, diphtheria, yaws, pinta, and bejel. penicillin G benzathine. Adults: 1.2 million units I.M. as a single injection. Children who weigh 27 kg (60 lb) or more: 900,000 units I.M. in a single injection.
Children who weigh less than 27 kg: 300,000 to 600,000 units I.M. in a single injection. Prophylaxis of poststreptococcal rheumatic fever. penicillin G benzathine. Adults and children: 1.2 million units I.M. once monthly. Syphilis of less than 1 year’s duration. penicillin G benzathine. Adults: 2.4 million units I.M. in a single dose. Syphilis of more than 1 year’s duration. penicillin G benzathine. Adults: 2.4 million units I.M. weekly for 3 successive weeks. Moderate to severe systemic infections. penicillin G potassium, sodium. Adults: 12 to 24 million units I.M. or I.V. daily, given in divided doses q 4 hours.
Children: 25,000 to 300,000 units/kg I.M. or I.V. daily, given in divided doses q 4 hours. Moderate to severe systemic infections, pneumococcal pneumonia. penicillin G procaine. Adults: 600,000 to 1.2 million units I.M. daily as a single dose or q 6 to 12 hours.
Children: 300,000 units I.M. daily as a single dose. Uncomplicated gonorrhea. penicillin G procaine. Adults and children older than age 12: 1 g probenecid P.O.; then, 30 minutes later, 4.8 million units of penicillin G procaine I.M., divided into two injection
sites. Anthrax. penicillin G potassium. Adults: 5 to 20 million units I.V. daily given in divided doses every 4 to 6 hours for at least 14 days after symptoms abate. Or,
80,000 units/kg of body weight in the first hour followed by a maintenance dose of 320,000 units/kg of body weight/day. The
average adult dose is 4 million units every 4 hours; can also be administered as 2 million units every 2 hours.
Children: 100,000 to 150,000 units/kg/day I.V. in divided doses every 4 to 6 hours for at least 14 days after symptoms abate. Anthrax caused by Bacillus anthracis, including inhalational anthrax (postexposure). penicillin G procaine. Adults: 1,200,000 units I.M. every 12 hours.
Children: 25,000 units/kg I.M. (maximum 1,200,000 units) every 12 hours. Cutaneous anthrax. penicillin G procaine. Adults: 600,000 to 1 million units/day I.M.
≡ Dosage adjustment. For patients with renal impairment, see below for adjustments of penicillin G potassium and penicillin G sodium. If patient
is uremic and creatinine clearance is more than 10 ml/minute, give full loading dose, then give 1/2 dose q 4 to 5 hr for additional
doses.
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Pharmacodynamics
Antibiotic action: Bactericidal. Adheres to penicillin-binding proteins, thus inhibiting bacterial cell wall synthesis. Spectrum of activity
includes most non-penicillinase-producing strains of gram-positive and gram-negative aerobic cocci, spirochetes, and some
gram-positive aerobic and anaerobic bacilli.
Pharmacokinetics
Absorption: Sodium and potassium salts of penicillin G absorbed rapidly after I.M. injection; peak serum levels within 15 to 30 minutes.
Slower absorption of other salts. Serum levels of penicillin G procaine peak in 1 to 4 hours, with drug detectable in serum
for 1 to 2 days; serum levels of penicillin G benzathine peak in 13 to 24 hours, with serum levels detectable for 1 to 4 weeks.
Distribution: Penicillin G distributed widely into synovial, pleural, pericardial, ascitic fluids; bile, liver, skin, lungs, kidneys, muscle,
intestines, tonsils, maxillary sinuses, saliva, and erythrocytes. Poor CSF penetration but enhanced in patients with inflamed
meninges. Penicillin G crosses the placental barrier; is 45% to 68% protein-bound.
Metabolism: Between 16% and 30% of I.M. dose metabolized to inactive compounds.
Excretion: Excreted primarily in urine by tubular secretion; 20% to 60% of dose recovered in 6 hours. Some drug appears in breast milk.
Elimination half-life in adults is about 1/2 to 1 hour. Severe renal impairment prolongs half-life; penicillin G is removed
by hemodialysis and is only minimally removed by peritoneal dialysis.
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Contraindications and precautions
Contraindicated in patients hypersensitive to drug or other penicillins. Use cautiously in patients with drug allergies (especially
to cephalosporins or imipenem). Penicillin G potassium is contraindicated in patients with renal failure.
Interactions
Drug-drug. Aminoglycosides: Causes synergistic therapeutic effects, chiefly against enterococci; this combination is most effective in enterococcal bacterial
endocarditis. However, drugs are physically and chemically incompatible; inactivated when mixed or given together. Administer separately.
Clavulanate: Enhances effect of penicillin G against certain beta-lactamase-producing bacteria. Clavulanate may be used for this purpose.
Heparin, oral anticoagulants: Increases risk of bleeding. Monitor PTT, PT, and INR.
Hormonal contraceptives: Decreases effectiveness. Suggest using alternative forms of contraception.
Methotrexate: Large doses of penicillin may interfere with renal tubular secretion of methotrexate; delays elimination and elevates serum
levels of methotrexate. Monitor patient for toxicity.
NSAIDs, sulfinpyrazone: Prolongs penicillin half-life. Monitor patient for effectiveness.
Potassium-sparing diuretics: May cause hyperkalemia when used with parenteral penicillin G potassium. Monitor serum potassium.
Probenecid: Blocks tubular secretion of penicillin, raising its serum levels. Probenecid may be used for this purpose.
Drug-herb. Guar gum: Decreases absorption of orally administered drugs. Advise patient to take drug 1 hour before or several hours after guar gum.
Adverse reactions
CNS: neuropathy, seizures, lethargy, hallucinations, anxiety, confusion, agitation, depression, dizziness, fatigue.
CV: thrombophlebitis (with penicillin G potassium only).
GI: nausea, vomiting, enterocolitis, pseudomembranous colitis.
GU: interstitial nephritis, nephropathy.
Hematologic: eosinophilia, hemolytic anemia, thrombocytopenia, leukopenia, anemia, agranulocytosis.
Metabolic: severe potassium poisoning with high doses (hyperreflexia, seizures, coma ).
Skin: pain and sterile abscess at injection site.
Other: hypersensitivity reactions (maculopapular and exfoliative dermatitis, chills, fever, edema, anaphylaxis ), overgrowth of nonsusceptible organisms (with penicillin G potassium and procaine).
Effects on lab test results
• May increase potassium level.
• May increase eosinophil count. May decrease hemoglobin, hematocrit, and platelet, WBC, and granulocyte counts.
Overdose and treatment
Signs and symptoms of overdose include neuromuscular irritability and seizures.
Drug can be removed by hemodialysis.
Special considerations 
ALERT Don’t confuse the various types of penicillin, polycillin, and penicillamine.
• Keep emergency equipment on hand to manage possible anaphylaxis.
• Because penicillins are dialyzable, patients undergoing hemodialysis may need dosage adjustments.
• Administer by deep I.M. injection in upper outer quadrant of buttock. In infants and small children, use midlateral aspect
of thigh. ALERT Never give penicillin G benzathine or penicillin G procaine by I.V. route. Inadvertent I.V. administration has caused cardiac
arrest and death.
• Drug can be given as a continuous infusion for meningitis.
• Monitor patient closely for possible hypernatremia (with sodium) or hyperkalemia (with potassium).
• Patients with poor renal function are predisposed to high blood levels, which may cause seizures. Monitor renal function.
• Penicillin G alters test results for urine and serum protein levels and interferes with turbidimetric methods using sulfosalicylic
acid, trichloroacetic acid, acetic acid, and nitric acid. It doesn’t interfere with tests using bromophenol blue (Albustix,
Albutest, Multistix), but alters urine glucose testing using cupric sulfate (Benedict’s reagent); use Diastix, Chemstrip uG,
or glucose enzymatic test strip instead. Penicillin G may cause falsely elevated results of urine specific gravity tests in
patients with low urine output and dehydration, and falsely elevated Norymberski and Zimmermann test results for 17-ketogenic
steroids; causes false-positive CSF protein test results (Folin-Ciocalteau method) and may cause positive Coombs’ test results.
• Penicillin G may falsely decrease serum aminoglycoside levels. Adding beta-lactamase to sample inactivates penicillin, rendering
assay more accurate. Or sample can be spun down and frozen immediately after collection.
Breast-feeding patients
• Drug appears in breast milk. Use in breast-feeding women may sensitize infant to penicillin.
Geriatric patients
• Half-life is prolonged in elderly patients because of impaired renal function.
Patient education
• Tell patient that drug must be injected deep into a large muscle mass.
• Instruct patient to report allergic symptoms and any adverse reactions.
Reactions may be common, uncommon, life-threatening, or
COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use