BICILLIN C-R 900/300- penicillin g benzathine and penicillin g procaine injection, suspension
King Pharmaceuticals, Inc.
Bicillin C-R 900/300 (penicillin G benzathine and penicillin G procaine injectable suspension) contains the equivalent of 900,000 units of penicillin G as the benzathine and 300,000 units of penicillin G as the procaine salts. It is available for deep intramuscular injection.
Penicillin G benzathine is prepared by the reaction of dibenzylethylene diamine with two molecules of penicillin G. It is chemically designated as (2S ,5R ,6R )-3,3-Dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid compound with N,N’ -dibenzylethylenediamine (2:1), tetrahydrate. It occurs as a white, crystalline powder and is very slightly soluble in water and sparingly soluble in alcohol. Its chemical structure is as follows:
Penicillin G procaine, (2S ,5R ,6R )-3,3-Dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid compound with 2-(diethylamino)ethyl p -aminobenzoate (1:1) monohydrate, is an equimolar salt of procaine and penicillin G. It occurs as white crystals or a white, microcrystalline powder and is slightly soluble in water. Its chemical structure is as follows:
Each 2 mL syringe contains the equivalent of 1,200,000 units of penicillin G as follows: penicillin G benzathine equivalent to 900,000 units of penicillin G and penicillin G procaine equivalent to 300,000 units of penicillin G in a stabilized aqueous suspension with sodium citrate buffer; and as w/v, approximately 0.5% lecithin, 0.55% carboxymethylcellulose, 0.55% povidone, 0.1% methylparaben, and 0.01% propylparaben.
Penicillin G benzathine and penicillin G procaine have a low solubility and, thus, the drugs are slowly released from intramuscular injection sites. The drugs are hydrolyzed to penicillin G. This combination of hydrolysis and slow absorption results in blood serum levels much lower but more prolonged than other parenteral penicillins. Intramuscular administration of 1,200,000 units of Bicillin C-R 900/300 in patients weighing 100 to 140 lbs. usually produces average blood levels of 0.24 units/mL at 24 hours, 0.039 units/mL at 7 days, and 0.024 units/mL at 10 days.
Approximately 60% of penicillin G is bound to serum protein. The drug is distributed throughout the body tissues in widely varying amounts. Highest levels are found in the kidneys with lesser amounts in the liver, skin, and intestines. Penicillin G penetrates into all other tissues and the spinal fluid to a lesser degree. With normal kidney function, the drug is excreted rapidly by tubular excretion. In neonates and young infants and in individuals with impaired kidney function, excretion is considerably delayed.
Penicillin G exerts a bactericidal action against penicillin-susceptible microorganisms during the stage of active multiplication. It acts through the inhibition of biosynthesis of cell-wall peptidoglycan, rendering the cell wall osmotically unstable resulting in death of the bacterium.
Penicillin is not active against penicillinase-producing bacteria, or against organisms resistant to beta-lactams because of alterations in the penicillin-binding proteins. Resistance to penicillin G has not been reported in Streptococcus pyogenes.
Penicillin has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section.
Beta-hemolytic streptococci (groups A, B, C, G, H, L and M)
Streptococcus pneumoniae (penicillin-susceptible isolates only)
When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drug products used in resident hospitals to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized test method (broth or agar). The MIC should be interpreted according to the following criteria.
Quantitative methods that require the measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method. This procedure uses paper discs impregnated with 10 units penicillin to test the susceptibility of bacteria to penicillin. The disc diffusion interpretive criteria are provided in the table below.
Streptococcus pyogenes (Group A)
|MIC (mcg/mL)||Disk Diffusion (zone diameter in mm)|
|Pathogen||Susceptible (S)||Intermediate (I)||Resistant (R)||Susceptible (S)||Intermediate (I)||Resistant (R)|
|Streptococcus pyogenes * , †||≤ 0.12||-||-||≥ 24||-||-|
Streptococcus pneumoniae (non-meningitis)
|≤ 2||Susceptible (S)|
A report of Susceptible indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations at the infection site necessary to inhibit growth of the pathogen. A report of Intermediate indicates that the results should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug product is physiologically concentrated or in situations where a high dosage of the drug can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of Resistant indicates that the antimicrobial is not likely to inhibit growth of the pathogen if the antimicrobial compound reaches the concentrations usually achievable at the infection site; other therapy should be selected.
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