Benzylpenicillin

Therapy Penicillin G Potassium Injection, USP is indicated in the treatment of serious infections caused by susceptible strains of the designated microorganisms in the conditions listed below. Appropriate culture and susceptibility tests should be done before treatment in order to isolate and identify organisms causing infection and to determine their susceptibility to penicillin G. Therapy with Penicillin G Potassium Injection, USP may be initiated before results of such tests are known when there is reason to believe the infection may involve any of the organisms listed below; however, once these results become available, appropriate therapy should be continued. …

• Penicillin G Potassium Injection, USP should be administered by intravenous infusion
• The usual dose recommendations are as follows: Adult patients (*) Because of its short half-life, Penicillin G is administered in divided doses, usually every 4-6 hours with the exception of meningococcal meningitis/septicemia, i.e. , every 2 hours
• CLINICAL INDICATION DOSAGE Serious infections due to susceptible strains of streptococci (including S. pneumoniae ) -septicemia, empyema, pneumonia, pericarditis, endocarditis and meningitis 12 to 24 million units/day depending on the infection and its severity administered in equally divided doses every 4-6 hours
• Serious infections due to susceptible strains of staphylococci - septicemia, empyema, pneumonia, pericarditis, endocarditis and meningitis 5 to 24 million units/day depending on the infection and its severity administered in equally divided doses every 4-6 hours
• Anthrax Minimum of 8 million units/day in divided doses every 6 hours
• Higher doses may be required depending on susceptibility of organism. …

• Incompletely developed renal function in newborns may delay elimination of penicillin; therefore, appropriate reductions in the dosage and frequency of administration should be made in these patients
• All newborns treated with penicillins should be monitored closely for clinical and laboratory evidence of toxic or adverse effects (see PRECAUTIONS )
• Pediatric doses are generally determined on a weight basis and should be calculated for each patient individually
• Recommended guidelines for pediatric dosages are presented in Dosage and Administration . …

Clinical studies of Penicillin G Injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. …

• Patients should be counseled that antibacterial drugs including Penicillin G Potassium Injection, USP should only be used to treat bacterial infections
• They do not treat viral infections (e.g., the common cold)
• When Penicillin G Potassium Injection, USP is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. …

• A history of a hypersensitivity (anaphylactic) reaction to any penicillin is a contraindication
• Solutions containing dextrose may be contraindicated in patients with known allergy to corn or corn products

Bacteriostatic antibacterials ( i.e. , chloramphenicol, erythromycins, sulfonamides or tetracyclines) may antagonize the bactericidal effect of penicillin, and concurrent use of these drugs should be avoided. This has been documented in vitro ; however, the clinical significance of this interaction is not well-documented. Penicillin blood levels may be prolonged by concurrent administration of probenecid which blocks the renal tubular secretion of penicillins. Other drugs may compete with penicillin G for renal tubular secretion and thus prolong the serum half-life of penicillin. …

Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients on penicillin therapy. These reactions are more likely to occur in individuals with a history of penicillin hypersensitivity and/or a history of sensitivity to multiple allergens. There have been reports of individuals with a history of penicillin hypersensitivity who have experienced severe reactions when treated with cephalosporins. Before initiating therapy with penicillin G, careful inquiry should be made concerning previous hypersensitivity reactions to penicillins, cephalosporins, or other allergens. …

Body as a whole: The Jarisch-Herxheimer reaction is a systemic reaction, that may occur after the initiation of penicillin therapy in patients with syphilis or other spirochetal infections ( i.e. , Lyme disease and Relapsing fever). The reaction begins one to two hours after initiation of therapy and disappears within 12 to 24 hours. It is characterized by fever, chills, myalgias, headache, exacerbation of cutaneous lesions, tachycardia, hyperventilation, vasodilation with flushing and mild hypotension. The pathogenesis of the Herxheimer reaction may be due to the release from the spirochetes of heat-stable pyrogen. …

Pregnancy Reproduction studies performed in the mouse, rat and rabbit have revealed no evidence of impaired fertility or harm to the fetus due to penicillin G. Human experience with the penicillins during pregnancy has not shown any positive evidence of adverse effects on the fetus. There are, however, no adequate and well controlled studies in pregnant women showing conclusively that harmful effects of these drugs on the fetus can be excluded. …

Dose related toxicity may arise with the use of massive doses of intravenous penicillins (40 to 100 million units per day), particularly in patients with severe renal impairment (see PRECAUTIONS ). The manifestations may include agitation, confusion, asterixis, hallucinations, stupor, coma, multifocal myoclonus, seizures and encephalopathy. Hyperkalemia is also possible (see ADVERSE REACTIONS -Metabolic). In case of overdosage, discontinue penicillin, treat symptomatically and institute supportive measures as required. …

Take it when you remember, unless it is nearly time for the next dose. Then skip the missed one. Never take two doses at once to make up for it. Check your leaflet, as some medicines are different.