penicillin G benzathine

Action

Inhibits biosynthesis of cell-wall mucopeptide; kills penicillin-susceptible bacteria during active multiplication stage

Availability

Suspension for I.M. injection: 600,000 units/ml in 1-, 2-, and 4-ml prefilled syringes

Indications and dosages

➣ Upper respiratory infections

Adults: 1.2 million units I.M. as a single dose

Children weighing 27 kg (60) or more: 900,000 units I.M. as a single dose

Infants and children weighing less than 27 kg (60 lb): 300,000 to 600,000 units I.M. as a single dose

➣ Early syphilis (primary, secondary, or latent)

Adults: 2.4 million units I.M. as a single dose

Children: 50,000 units/kg I.M. as a single dose, increased as needed up to adult dosage

➣ Congenital syphilis

Children younger than age 2: 50,000 units/kg I.M. as a single dose

➣ Late (tertiary) syphilis and neurosyphilis

Adults: 2.4 million units I.M. q week for up to 3 weeks, after aqueous penicillin G or procaine penicillin therapy

➣ Gummas and cardiovascular syphilis

Adults: 2.4 million units I.M. q week for 3 weeks

➣ Yaws, bejel, and pinta

Adults: 1.2 million units I.M. as a single dose

➣ Prophylaxis of rheumatic fever and glomerulonephritis

Adults: After acute attack, 1.2 million units I.M. q month or 600,000 units q 2 weeks

Contraindications

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

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, and benzathine. Be aware that cross-sensitivity to cephalosporins and imipenem also may occur.

See Do not give intravenously

• Inject deep I.M. into upper outer quadrant of buttock in adult or mid-lateral thigh in infant or small child. Don't inject into gluteal muscle in child younger than age 2. Rotate injection sites with repeated doses.

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

• Be aware that Hoigne's syndrome (transient bizarre behavior and neurologic reactions) may immediately follow I.M. injection.

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

Adverse reactions

CNS: headache, lethargy, hallucinations, anxiety, neuropathy, fatigue, nervousness, tremors, euphoria, asthenia, Hoigne's syndrome, cerebrovascular accident, seizures, coma

CV: hypotension, pulmonary hypertension, vasodilation, vasovagal reaction, syncope, palpitations, tachycardia, cardiac arrest, pulmonary embolism

EENT: blurred vision, vision loss, laryngeal edema

GI: nausea, vomiting, diarrhea, epigastric distress, abdominal pain, colitis, blood in stool, glossitis, pseudomem-branous colitis

GU: hematuria, proteinuria, urogenic bladder, erectile dysfunction, priapism, nephropathy, renal failure

Hematologic: hemolytic anemia, leukopenia, thrombocytopenia

Metabolic: hypernatremia, hyper-kalemia

Respiratory: dyspnea, hypoxia, apnea, pulmonary embolism

Skin: rash, urticaria, sweating

Other: fever, superinfection, injection site reactions and pain, Jarisch-Hersheimer reaction, 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, blood urea nitrogen, creatinine, 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 anaphylaxis and serum sickness.

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

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

See Watch for evidence of superinfection and pseudomembranous colitis.

Patient teaching

See Teach patient to recognize anaphylaxis symptoms and 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.

• Advise patient to contact prescriber if infection symptoms get worse.

• Tell female patient that drug may make hormonal contraceptives ineffective. Advise her to use barrier birth control 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.