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Penicillin G Benzathine

Medically reviewed by Last updated on Dec 16, 2018.


(pen i SIL in jee BENZ a theen)

Index Terms

  • Benzathine Benzylpenicillin
  • Benzathine Penicillin G
  • Benzylpenicillin Benzathine

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Suspension, Intramuscular:

Bicillin L-A: 600,000 units/mL (1 mL); 1,200,000 units/2 mL (2 mL); 2,400,000 units/4 mL (4 mL) [contains methylparaben, propylparaben]

Brand Names: U.S.

  • Bicillin L-A

Pharmacologic Category

  • Antibiotic, Penicillin


Interferes with bacterial cell wall synthesis during active multiplication, causing cell wall death and resultant bactericidal activity against susceptible bacteria


IM: Slow


Minimal concentrations attained in CSF with inflamed or uninflamed meninges; highest levels in the kidney; lesser amounts in liver, skin, intestines


Excreted by renal tubular excretion; penicillin G is detected in urine for up to 12 weeks after a single IM injection; renal clearance is delayed in neonates, young infants, and patients with impaired renal function

Time to Peak

Serum: Within 12 to 24 hours; serum levels are usually detectable for 1 to 4 weeks depending on the dose; larger doses result in more sustained levels rather than higher levels

Duration of Action

Dose dependent: 1 to 4 weeks; larger doses result in more sustained levels

Protein Binding


Use: Labeled Indications

Acute glomerulonephritis: Prophylaxis (secondary) in patients with a history of acute glomerulonephritis

Respiratory tract infections: Treatment of mild to moderate upper respiratory tract infections (including pharyngitis) caused by streptococci susceptible to low, prolonged serum concentrations of penicillin G

Rheumatic fever and chorea: Prophylaxis (secondary) of rheumatic fever and/or chorea

Rheumatic heart disease: Prophylaxis (secondary) in patients with rheumatic heart disease

Syphilis and other venereal diseases: Treatment of syphilis, yaws, bejel, and pinta

Off Label Uses

Streptococcal (group A) chronic carriage

Based on the IDSA guidelines for diagnosis and management of group A streptococcal pharyngitis, penicillin G benzathine, in combination with rifampin, is an effective and recommended agent for the treatment of chronic group A streptococcus carriage.


Hypersensitivity to penicillin(s) or any component of the formulation

Dosing: Adult

Usual dosage range: IM: 1.2 to 2.4 million units as a single dose

Streptococcus (group A):

Pharyngitis, acute treatment: IM: 1.2 million units as a single dose (AHA [Gerber 2009]; IDSA [Shulman 2012])

Secondary prophylaxis for rheumatic fever (prevention of recurrent attacks): IM: 1.2 million units once every 21 to 28 days. Duration depends on risk factors and presence of valvular heart disease (AHA [Gerber 2009]).

Manufacturer's labeling: Dosing in the prescribing information may not reflect current clinical practice. IM: 600,000 units every 2 weeks

Secondary prophylaxis of glomerulonephritis: IM: 1.2 million units every 4 weeks or 600,000 units twice monthly

Chronic carriage (off-label use): IM: 1.2 million units as a single dose in combination with oral rifampin. Note: Most individuals with chronic carriage do not require antibiotics (IDSA [Shulman 2012]).

Syphilis (CDC [Workowski 2015]):

Primary, Secondary, Early Latent (<1 year duration): IM: 2.4 million units as a single dose

Late Latent, Latent with unknown duration, or Tertiary Syphilis (with normal CSF examination): IM: 2.4 million units once weekly for 3 doses

Neurosyphilis (including Ocular Syphilis): Not indicated for initial treatment; aqueous penicillin G IV is preferred initial therapy (refer to Penicillin G Parenteral/Aqueous monograph for dosing). Following penicillin G IV initial treatment, may consider administration of penicillin G benzathine 2.4 million units IM once weekly for 3 weeks to provide a comparable total duration of therapy as for latent syphilis.

Yaws, bejel, and pinta: IM: 1.2 million units as a single dose

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Group A streptococcal upper respiratory infection (Gerber, 2009): Infants, Children, and Adolescents: IM:

Rheumatic fever, primary prevention:

≤27 kg: 600,000 units as a single dose

>27 kg: 1.2 million units as a single dose

Rheumatic fever, secondary prevention: Note: Duration of secondary rheumatic fever prophylaxis varies: Rheumatic fever with carditis and residual heart disease: 10 years or until 40 years of age (whichever is longer), sometimes lifelong prophylaxis; rheumatic fever with carditis but no residual heart disease: 10 years or until 21 years of age (whichever is longer); rheumatic fever without carditis: 5 years or until 21 years of age (whichever is longer)

≤27 kg: 600,000 units every 3-4 weeks

>27 kg: 1.2 million units every 3-4 weeks

Syphilis: (CDC, 2010; Red Book, 2012): Infants, Children, and Adolescents: IM

Primary, Secondary, or Early Latent (<1 year duration): 50,000 units/kg once; maximum dose: 2.4 million units

Late Latent or Latent with unknown duration: 50,000 units/kg once weekly for 3 doses; maximum dose: 2.4 million units


IM: Warm to room temperature before administration to lessen the pain associated with injection. Administer by deep IM injection at a slow, steady rate in the dorsogluteal region (upper outer quadrant of the buttock) or the ventrogluteal region. Do not inject near an artery or a nerve; permanent neurological damage or gangrene may result. When doses are repeated, rotate the injection site. Do not administer IV, intra-arterially, or SubQ.


Store at 2°C to 8°C (36°F to 46°F); do not freeze. Extended storage information at room temperature may be available; contact product manufacturer to obtain current recommendations.

Drug Interactions

Acemetacin: May increase the serum concentration of Penicillins. Monitor therapy

BCG (Intravesical): Antibiotics may diminish the therapeutic effect of BCG (Intravesical). Avoid combination

BCG Vaccine (Immunization): Antibiotics may diminish the therapeutic effect of BCG Vaccine (Immunization). Monitor therapy

Cholera Vaccine: Antibiotics may diminish the therapeutic effect of Cholera Vaccine. Management: Avoid cholera vaccine in patients receiving systemic antibiotics, and within 14 days following the use of oral or parenteral antibiotics. Avoid combination

Lactobacillus and Estriol: Antibiotics may diminish the therapeutic effect of Lactobacillus and Estriol. Monitor therapy

Methotrexate: Penicillins may increase the serum concentration of Methotrexate. Monitor therapy

Mycophenolate: Penicillins may decrease serum concentrations of the active metabolite(s) of Mycophenolate. This effect appears to be the result of impaired enterohepatic recirculation. Monitor therapy

Nitisinone: May increase the serum concentration of OAT3 Substrates. Monitor therapy

Probenecid: May increase the serum concentration of Penicillins. Management: Avoid the routine use of penicillins and probenecid, but this combination may be used advantageously in select cases with careful monitoring. Monitor for toxic effects of penicillins if probenecid is initiated or the dose is increased. Consider therapy modification

Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Consider therapy modification

Teriflunomide: May increase the serum concentration of OAT3 Substrates. Monitor therapy

Tetracyclines: May diminish the therapeutic effect of Penicillins. Consider therapy modification

Tolvaptan: May increase the serum concentration of OAT3 Substrates. Consider therapy modification

Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Vaccination with live attenuated typhoid vaccine (Ty21a) should be avoided in patients being treated with systemic antibacterial agents. Use of this vaccine should be postponed until at least 3 days after cessation of antibacterial agents. Consider therapy modification

Vitamin K Antagonists (eg, warfarin): Penicillins may enhance the anticoagulant effect of Vitamin K Antagonists. Monitor therapy

Test Interactions

Positive Coombs' [direct], false-positive urinary and/or serum proteins; false-positive or negative urinary glucose using Clinitest®

Adverse Reactions

Frequency not defined:

Cardiovascular: Cerebrovascular accident, hypotension, palpitations, syncope, tachycardia, vasodilatation, vasospasm, vasodepressor syncope

Central nervous system: Anxiety, coma, confusion, dizziness, drowsiness, euphoria, fatigue, headache, localized warm feeling, nervousness, neurologic abnormality (neurogenic bladder), numbness, pain, seizure, transverse myelitis

Dermatologic: Diaphoresis, gangrene of skin or other tissue, pallor, skin mottling, skin ulceration at injection site

Gastrointestinal: Bloody stools, intestinal necrosis, nausea, vomiting

Genitourinary: Hematuria, impotence, priapism, proteinuria

Hematologic & oncologic: Local hemorrhage (at injection site), lymphadenopathy

Hepatic: Increased serum AST

Hypersensitivity: Hypersensitivity reaction

Immunologic: Jarisch-Herxheimer reaction

Local: Abscess at injection site, atrophy at injection site, bruising at injection site, cellulitis at injection site, localized edema (at injection site), inflammation at injection site, injection site reaction (neurovascular damage), pain at injection site, residual mass at injection site, tissue necrosis at injection site

Neuromuscular & skeletal: Arthropathy, exacerbation of arthritis, periosteal disease (periostitis), rhabdomyolysis, tremor, weakness

Ophthalmic: Blindness, blurred vision

Renal: Increased blood urea nitrogen, increased serum creatinine, myoglobinuria, renal failure

Respiratory: Cyanosis

ALERT: U.S. Boxed Warning

Appropriate administration:

Not for IV use. Do not inject IV or admix with other IV solutions. There have been reports of inadvertent IV administration of penicillin G benzathine that has been associated with cardiorespiratory arrest and death. Prior to administration of this drug, carefully read the Warnings, Adverse Reactions, Dosage, and Administration sections of the labeling.


Concerns related to adverse effects:

• Hypersensitivity reactions: Serious and occasionally severe or fatal hypersensitivity (anaphylactic) reactions have been reported in patients on penicillin therapy, especially with a history of beta-lactam hypersensitivity (including cephalosporins), history of sensitivity to multiple allergens, or previous IgE-mediated reactions (eg, anaphylaxis, angioedema, urticaria). Serious anaphylactic reactions require immediate emergency treatment with epinephrine, oxygen, intravenous steroids and airway management (including intubation) as indicated.

• Superinfection: Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months postantibiotic treatment.

Disease-related concerns:

• Renal impairment: Use with caution in patients with renal impairment.

• Seizure disorders: Use with caution in patients with a history of seizure disorder; high levels, particularly in the presence of renal impairment, may increase risk of seizures.

• Syphilis/neurosyphilis use: CDC and AAP do not currently recommend the use of penicillin G benzathine for the initial treatment regimen for congenital syphilis or neurosyphilis due to reported treatment failures and lack of published clinical data on its efficacy (CDC [Workowski 2015]).

Other warnings/precautions:

• Appropriate administration: [US Boxed Warning]: Not for intravenous use; cardiopulmonary arrest and death have occurred from inadvertent IV administration. Administer by deep IM injection only. Quadriceps femoris fibrosis and atrophy have been reported after repeated IM injections of penicillin preparations into the anterolateral thigh. Injection into or near an artery or nerve could result in severe neurovascular damage or permanent neurological damage.

• Appropriate use: Use only for treatment of infections due to penicillin G sensitive gram positive organisms, few gram-negative organisms such as Neisseria gonorrhoeae, and some anaerobes and spirochetes. Use only for infections susceptible to the low and very prolonged serum concentrations of benzathine penicillin G.

• Prolonged use: Extended duration of therapy or use associated with high serum concentrations (eg, in renal insufficiency) may be associated with an increased risk for some adverse reactions (neutropenia, hemolytic anemia, serum sickness).

Monitoring Parameters

Observe for signs and symptoms of anaphylaxis during first dose

Pregnancy Considerations

Adverse events have not been observed in animal reproduction studies. Penicillin G benzathine crosses the placenta (Nathan 1993; Weeks 1997). Maternal use of penicillins has generally not resulted in an increased risk of adverse fetal effects. Penicillin G is the drug of choice for treatment of syphilis during pregnancy (CDC [Workowski 2015]).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience headache, nausea, vomiting, tremors, fatigue, or diarrhea. Have patient report immediately to prescriber signs of kidney problems (urinary retention, hematuria, change in amount of urine passed, or weight gain); chills; edema; joint pain; severe dizziness; passing out; severe loss of strength and energy; bruising; bleeding; angina; tachycardia; abnormal heartbeat; shortness of breath; signs of severe cerebrovascular disease (change in strength on one side is greater than the other, difficulty speaking or thinking, change in balance, or vision changes); black, tarry, or bloody stools; severe abdominal pain; swollen glands; confusion; anxiety; seizures; sweating a lot; vision changes; sexual dysfunction; priapism; injection site lump, scab, hardness, or irritation; numbness; tingling; weakness; or signs of Clostridium difficile (C. diff)-associated diarrhea (abdominal pain or cramps, severe diarrhea or watery stools, or bloody stools) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.