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Drugs reference index «Penicillin G»

Penicillin G
Penicillin G

Penicillin G

Pronunciation: (pen-ih-SILL-in G)Class: Natural penicillin Penicillin G Potassium

Trade Names:Pfizerpen- Powder for injection 1,000,000 units- Powder for injection 5,000,000 units- Powder for injection 20,000,000 units

Penicillin G Procaine

Trade Names:Wycillin- Injection, IM 600,000 units- Injection, IM 1,200,000 units- Injection, IM 2,400,000 units

Penicillin G Sodium

Trade Names:Penicillin G Sodium- Powder for injection 5,000,000

Crystapen (Canada)Penicillin G Benzathine

Trade Names:Bicillin L-A- Injection, IM 300,000 units/mL- Injection, IM 600,000 units/dose- Injection, IM 1,200,000 units/dose- Injection, IM 2,400,000 units/dose

Trade Names:Permapen- Injection 1,200,000 units/dose


Inhibits mucopeptide synthesis of bacterial cell wall.



Varies considerably, 15% to 30% (oral) and slow absorption (IM). T max is 1 to 2 h (oral), 24 h (benzathine IM), and 4 h (procaine IM). C max is 2.2 to 17 mcg/mL (IV), 0.03 to 0.05 mcg/mL (benzathine IM).


Distributed throughout body tissues; highest levels found in kidneys with lesser amount in liver, skin, and intestines. Also, penetrates CSF; however, concentrations are low with noninflammed meninges, as is penetration in purulent bronchial secretions. Protein binding is 60% (oral), primarily albumin. Vd is 0.5 to 0.7 L/kg (oral). Crosses the placenta; distributes into breast milk.


Hepatic metabolism accounts for less than 30% of the biotransformation.


Renal (largely unchanged); hepatic inactivation and excretion in bile; t ½ 1.4 h or less.


Sustaining levels for up to 4 wk (benzathine).

Special Populations

Renal Function Impairment

Neonates and young infants with impaired renal function have delayed excretion.

Indications and Usage

Penicillin G

Treatment of infections caused by susceptible microorganisms.

Penicillin G Procaine

Treatment of moderately severe infections caused by penicillin G–sensitive microorganisms that are sensitive to low and persistent serum levels achieved with this dose form.

Penicillin G Benzathine

Mild to moderate upper respiratory tract infections, venereal diseases, and prophylaxis of rheumatic fever or chorea caused by penicillin G–sensitive microorganisms that are susceptible to the low and very prolonged serum levels common to this dosage form.


Hypersensitivity to penicillins. Do not treat severe pneumonia, empyema, bacteremia, pericarditis, meningitis, and purulent or septic arthritis with oral penicillin G during acute stage.

Dosage and Administration

Dosage may vary with site of infection and organism being treated.

Penicillin G (Aqueous Potassium or Sodium)Adults

IV / IM 1 to 24 million units/day in divided doses every 4 to 6 h.


IV / IM 100,000 to 250,000 units/kg/day in divided doses every 4 h.

Infants (older than 7 days of age and more than 2,000 g)

IV / IM 100,000 units/kg/day in divided doses every 6 h (meningitis: 200,000 units/kg/day in divided doses every 6 h).

Infants (younger than 7 days of age and more than 2,000 g)

IV / IM 50,000 units/kg/day in divided doses every 8 h (meningitis: 150,000 units/kg/day in divided doses every 8 h).

Infants (younger than 7 days of age and less than 2,000 g)

IV / IM 50,000 units/kg/day in divided doses every 12 h (meningitis: 100,000 units/kg/day in divided doses every 12 h).

Penicillin G PotassiumAdults and children older than 12 yr of age

PO 200,000 to 500,000 units every 6 to 8 h.

Infants and children younger than 12 yr of age

PO 25,000 to 90,000 units/kg/day in 3 to 6 divided doses.

Penicillin G Procaine (Aqueous)Adults and children (at least 27 kg)

IM 600,000 to 1.2 million units/day in 1 to 2 doses.

Children (under 27 kg)

IM 300,000 units/day.

Congenital Syphilis Children (under 32 kg)

IM 50,000 units/kg/day as a single dose for 10 to 14 days.

Neurosyphilis Adults

IM 2.4 million units/day plus probenecid 500 mg PO 4 times daily, both for 10 to 14 days.

Penicillin G BenzathineAdults

IM 1.2 to 2.4 million units in 1 dose.

Children more than 27 kg

IM 900,000 to 1.2 million units in 1 dose.

Children and infants less than 27 kg

IM 300,000 to 1.2 million units in 1 dose.


IM 50,000 units/kg in 1 dose.

General Advice

  • Depending on route of administration, prepare solution using sterile water for injection, isotonic sodium chloride injection, or dextrose injection.
  • For IM administration, inject deeply into upper outer quadrant of buttock in adults. In infants and small children, inject in midlateral aspect of thigh. With repeated doses, rotate injection sites.
  • For IV administration, administer continuously or intermittently. For intermittent infusion, infuse each dose over 1 to 2 h (adults) or 15 to 30 min (newborns and children).


  • Solutions prepared for IV infusion are stable at room temperature for at least 24 h or for 1 wk if refrigerated (36° to 46°F).
  • Dry powder is stable and does not require refrigeration.
  • Thaw premixed frozen solution at room temperature (77°F) or in refrigerator (36° to 46°F). Do not force thaw by immersion in water bath or microwave irradiation. Thawed solution is stable for 24 h at room temperature or for 14 days if refrigerated (36° to 46°F). Do not refreeze thawed solution.

Drug Interactions

Anticoagulants (oral and heparin)

May increase bleeding risks of anticoagulant by prolonging bleeding time.


May potentiate anaphylactic reactions of penicillin.


May cause synergism or antagonism to develop.

Contraceptives, oral

May reduce efficacy of oral contraceptives.


May cause synergism or antagonism to develop.


Increases penicillin serum concentration.


May impair bactericidal effects of penicillin G.


Aminoglycosides, parenteral

Penicillin may inactivate aminoglycosides in vitro; do not mix in same IV solution. May be used in combination for synergy if administered separately.

Carbohydrate solutions at alkaline pH

Penicillin solutions are rapidly inactivated.

Laboratory Test Interactions

Antiglobulin (Coombs test)

Drug may cause false-positive results.

Urine glucose test

Drug may cause false-positive results with copper sulfate tests (Benedict test, Fehling test, or Clinitest tablets); enzyme-based tests (eg, Clinistix , Tes-tape ) are not affected.

Urine protein determinations

Drug may cause false-positive reactions with sulfosalicylic acid and boiling test, acetic acid test, biuret reaction, and nitric acid test; bromphenol blue test ( Multi-Stix ) is not affected.

Adverse Reactions


Dizziness; fatigue; insomnia; reversible hyperactivity; neurotoxicity (eg, lethargy, neuromuscular irritability, hallucinations, convulsions, seizures).


Itchy eyes; stomatitis; gastritis; sore mouth or tongue; furry tongue; black “hairy” tongue; abnormal taste perception.


Glossitis; dry mouth; nausea; anorexia; vomiting; abdominal pain or cramp; epigastric distress; diarrhea or bloody diarrhea; rectal bleeding; flatulence; enterocolitis; pseudomembranous colitis.


Interstitial nephritis (eg, oliguria, proteinuria, hematuria, hyaline casts, pyuria); nephropathy; increased BUN and creatinine.


Decreased hemoglobin, hematocrit, RBC, WBC, neutrophils, lymphocytes, platelets; increased lymphocytes, monocytes, basophils, eosinophils and platelets; abnormal coagulation tests.


Elevated serum alkaline phosphatase, hypernatremia; hypokalemia; hyperkalemia.


Hypersensitivity reactions (eg, urticaria, angioneurotic edema, laryngospasm, laryngeal edema, bronchospasm, hypotension, vascular collapse, death, maculopapular to exfoliative dermatitis, vesicular eruptions, erythema multiforme, serum sickness, skin rashes); vaginitis; hyperthermia.



Category B .


Small amount excreted in breast milk. May cause diarrhea, candidiasis, or allergic response in breast-feeding infant.


Reactions range from mild to life-threatening. Administer drug with caution to cephalosporin-sensitive patients because of possible crossreactivity.

Renal Function

Use drug with caution; may require dosage adjustment.


May result in bacterial or fungal overgrowth of nonsusceptible organisms.

Tartrazine Sensitivity

Some products contain tartrazine, which may cause allergic-type reactions in susceptible individuals.

Electrolyte content

Penicillin G aqueous sodium contains 2 mEq sodium per 1 million units. Penicillin G aqueous potassium contains 1.7 mEq potassium and 0.3 mEq sodium per 1 million units. Beware of iatrogenic electrolyte abnormalities and fluid overload.

Procaine sensitivity

If sensitivity to procaine in penicillin G procaine is suspected, inject 0.1 mL of procaine 1% to 2% solution intradermally. If erythema, wheal, flare, or eruption develops, do not use procaine penicillin preparations.

Pseudomembranous colitis

May occur because of overgrowth of clostridia.



Neuromuscular hyperexcitability, convulsions, agitation, confusion, asterixis, hallucinations, stupor, coma, multifocal myoclonus, seizures, encephalopathy, hyperkalemia.

Patient Information

  • Instruct patient to finish course of therapy even if feeling better.
  • Advise patient to take oral penicillin at intervals around clock on empty stomach 1 h before or 2 h after meal with full glass of water, not fruit juice or carbonated beverage.
  • Instruct penicillin allergic patient to carry medical identification (eg, card, bracelet).
  • Advise patient to use nonhormonal form of contraceptive while taking penicillin.
  • Inform patient of signs of hypersensitivity (eg, skin rash, itching, hives, shortness of breath, wheezing) and other side effects, such as black tongue, sore throat, nausea, vomiting, severe diarrhea, fever, swollen joints, and instruct patient to notify health care provider should they occur.
  • Instruct patient to notify health care provider if there is no improvement in symptoms of infection.
  • Advise patient to notify health care provider of signs of superinfection (eg, vaginitis, black “hairy” tongue).

Copyright © 2009 Wolters Kluwer Health.

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