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Pfizerpen (Penicillin G Potassium) - Indications and Dosage



Aqueous penicillin G (parenteral) is indicated in the therapy of severe infections caused by penicillin G-susceptible microorganisms when rapid and high penicillin levels are required in the conditions listed below. Therapy should be guided by bacteriological studies (including susceptibility tests) and by clinical response.

The following infections will usually respond to adequate dosage of aqueous penicillin G (parenteral):

  • Streptococcal infections.

NOTE: Streptococci in groups A, C, H, G, L, and M are very sensitive to penicillin G. Some group D organisms are sensitive to the high serum levels obtained with aqueous penicillin G.

Aqueous penicillin G (parenteral) is the penicillin dosage form of choice for bacteremia, empyema, severe pneumonia, pericarditis, endocarditis, meningitis, and other severe infections caused by sensitive strains of the gram-positive species listed above.

  • Pneumococcal infections.
  • Staphylococcal infections–penicillin G sensitive.
  • Other infections: Anthrax.
  • Actinomycosis.
  • Clostridial infections (including tetanus).
  • Diphtheria (to prevent carrier state).
  • Erysipeloid (Erysipelothrix insidiosa) endocarditis.
  • Fusospirochetal infections–severe infections of the oropharynx (Vincent's), lower respiratory tract and genital area due to Fusobacterium fusiformisans spirochetes.
  • Gram-negative bacillary infections (bacteremias)–(E. coli, A. aerogenes, A. faecalis, Salmonella, Shigella and P. mirabilis).
  • Listeria infections (Listeria monocytogenes).
  • Meningitis and endocarditis.
  • Pasteurella infections (Pasteurella multocida).
  • Bacteremia and meningitis.
  • Rat-bite fever (Spirillum minus or Streptobacillus moniliformis).
  • Gonorrheal endocarditis and arthritis (N. gonorrhoeae).
  • Syphilis (T. pallidum) including congenital syphilis.
  • Meningococcic meningitis.

Although no controlled clinical efficacy studies have been conducted, aqueous crystalline penicillin G for injection and penicillin G procaine suspension have been suggested by the American Heart Association and the American Dental Association for use as part of a combined parenteral-oral regimen for prophylaxis against bacterial endocarditis in patients with congenital heart disease or rheumatic, or other acquired valvular heart disease when they undergo dental procedures and surgical procedures of the upper respiratory tract.1 Since it may happen that alpha hemolytic streptococci relatively resistant to penicillin may be found when patients are receiving continuous oral penicillin for secondary prevention of rheumatic fever, prophylactic agents other than penicillin may be chosen for these patients and prescribed in addition to their continuous rheumatic fever prophylactic regimen.

NOTE: When selecting antibiotics for the prevention of bacterial endocarditis, the physician or dentist should read the full joint statement of the American Heart Association and the American Dental Association.1

To reduce the development of drug-resistant bacteria and maintain effectiveness of Pfizerpen and other antibacterial drugs, Pfizerpen should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.


Severe infections due to Susceptible Strains of Streptococci, Pneumococci, and Staphylococci–bacteremia, pneumonia, endocarditis, pericarditis, empyema, meningitis, and other severe infections–a minimum of 5 million units daily.

Syphilis–Aqueous penicillin G may be used in the treatment of acquired and congenital syphilis, but because of the necessity of frequent dosage, hospitalization is recommended. Dosage and duration of therapy will be determined by age of patient and stage of the disease.

Gonorrheal endocarditis–a minimum of 5 million units daily.

Meningococcic meningitis–1–2 million units intramuscularly every 2 hours, or continuous IV drip of 20–30 million units/day.

Actinomycosis–1–6 million units/day for cervicofacial cases; 10–20 million units/day for thoracic and abdominal disease.

Clostridial infections–20 million units/day; penicillin is adjunctive therapy to antitoxin.

Fusospirochetal infections–severe infections of oropharynx, lower respiratory tract, and genital area–5–10 million units/day.

Rat-bite fever (Spirillum minus or Streptobacillus moniliformis)–12–15 million units/day for 3–4 weeks.

Listeria infections (Listeria monocytogenes)
Neonates–500,000 to 1 million units/day.
Adults with meningitis–15–20 million units/day for 2 weeks.
Adults with endocarditis–15–20 million units/day for 4 weeks.

Pasteurella infections (Pasteurella multocida)
Bacteremia and meningitis 4–6 million units/day for 2 weeks.

Erysipeloid (Erysipelothrix insidiosa)
Endocarditis–2–20 million units/day for 4–6 weeks.

Gram-negative bacillary infections (E. coli, Enterobacter aerogenes, A. faecalis, Salmonella, Shigella and Proteus mirabilis)
Bacteremia–20–80 million units/day.

Diphtheria (carrier state)–300,000–400,000 units of penicillin/day in divided doses for 10–12 days.

Anthrax–A minimum of 5 million units of penicillin/day in divided doses until cure is effected.

For prophylaxis against bacterial endocarditis1 in patients with congenital heart disease or rheumatic or other acquired valvular heart disease, when undergoing dental procedures or surgical procedures of the upper respiratory tract, use a combined parenteral-oral regimen. One million units of aqueous crystalline penicillin G (30,000 units/kg in children) intramuscularly, mixed with 600,000 units procaine penicillin G (600,000 units for children) should be given one-half to one hour before the procedure. Oral penicillin V (phenoxymethyl penicillin), 500 mg for adults or 250 mg for children less than 60 lb, should be given every 6 hours for 8 doses. Doses for children should not exceed recommendations for adults for a single dose or for a 24 hour period.


The following table shows the amount of solvent required for solution of various concentrations:

Approx. Desired
Approx. Volume (mL)
Solvent for Vial of
Infusion Only
50,000 20.0
100,000 10.0
250,000 4.0 18.2 75.0
500,000 1.8 8.2 33.0
750,000 4.8
1,000,000 3.2 11.5

When the required volume of solvent is greater than the capacity of the vial, the penicillin can be dissolved by first injecting only a portion of the solvent into the vial, then withdrawing the resultant solution and combining it with the remainder of the solvent in a larger sterile container.

Buffered Pfizerpen (penicillin G potassium) for Injection is highly water soluble. It may be dissolved in small amounts of Water for Injection, or Sterile Isotonic Sodium Chloride Solution for Parenteral Use. All solutions should be stored in a refrigerator. When refrigerated, penicillin solutions may be stored for seven days without significant loss of potency.

Buffered Pfizerpen for Injection may be given intramuscularly or by continuous intravenous drip for dosages of 500,000, 1,000,000, or 5,000,000 units. It is also suitable for intrapleural, intraarticular, and other local instillations.


(1) Intramuscular Injection

Keep total volume of injection small. The intramuscular route is the preferred route of administration. Solutions containing up to 100,000 units of penicillin per mL of diluent may be used with a minimum of discomfort. Greater concentration of penicillin G per mL is physically possible and may be employed where therapy demands. When large dosages are required, it may be advisable to administer aqueous solutions of penicillin by means of continuous intravenous drip.

(2) Continuous Intravenous Drip

Determine the volume of fluid and rate of its administration required by the patient in a 24 hour period in the usual manner for fluid therapy, and add the appropriate daily dosage of penicillin to this fluid. For example, if an adult patient requires 2 liters of fluid in 24 hours and a daily dosage of 10 million units of penicillin, add 5 million units to 1 liter and adjust the rate of flow so the liter will be infused in 12 hours.

(3) Intrapleural or Other Local Infusion

If fluid is aspirated, give infusion in a volume equal to ¼ or ½ the amount of fluid aspirated, otherwise, prepare as for intramuscular injection.

(4) Intrathecal Use

The intrathecal use of penicillin in meningitis must be highly individualized. It should be employed only with full consideration of the possible irritating effects of penicillin when used by this route. The preferred route of therapy in bacterial meningitides is intravenous, supplemented by intramuscular injection.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Sterile solution may be left in refrigerator for one week without significant loss of potency.


Buffered Pfizerpen (penicillin G potassium) for Injection is available in vials containing respectively 5,000,000 units × 10's (NDC 0049-0520-44) and 20,000,000 units × 1's (NDC 0049-0530-44); buffered with sodium citrate and citric acid to an optimum pH.

Each million units contains approximately 6.8 milligrams of sodium (0.3 mEq) and 65.6 milligrams of potassium (1.68 mEq).

Store the dry powder below 86°F (30°C).

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