Penicillin G sodium is available as a powder in vials containing 5 million units of penicillin G as the sodium salt with sodium citrate and citric acid as buffers.3913 Depending on the intended route of administration, reconstitute the vials with sterile water for injection, dextrose 5%, or sodium chloride 0.9%; reconstitution of the 5 million-unit vial with 3 or 8 mL of diluent results in a final penicillin G concentration of 1 million or 500,000 units/mL, respectively.3913 To reconstitute the drug, loosen the powder in the vial; while holding the vial horizontally, rotate it and add the diluent slowly, directing the stream against the wall of the vial.3913 Shake the vial vigorously.3913
pH
Freshly reconstituted solutions have a pH ranging from 5 to 7.5.3913
Osmolality
Penicillin G sodium 250,000 units/mL in sterile water for injection has an osmolality of 795 mOsm/kg.50
The osmolality of penicillin G sodium was calculated for the following dilutions:1054
| Osmolality (mOsm/kg) | ||
|---|---|---|
| Penicillin G in Diluent | 50 mL | 100 mL |
| 3 million units in Dextrose 5% | 413 | 341 |
| 3 million units in Sodium chloride 0.9% | 439 | 368 |
| 5 million units in Dextrose 5% | 502 | 394 |
| 5 million units in Sodium chloride 0.9% | 529 | 421 |
The following maximum penicillin G sodium concentrations were recommended to achieve osmolalities suitable for peripheral infusion in fluid-restricted patients:1180
| Diluent | Maximum Concentration (units/mL) | Osmolality (mOsm/kg) |
|---|---|---|
| Dextrose 5% | 85,383 | 573 |
| Sodium chloride 0.9% | 76,891 | 563 |
| Sterile water for injection | 154,091 | 545 |
Sodium Content
Penicillin G sodium contains 1.68 mEq of sodium per million units of penicillin G.3913
NOTE: Do not confuse other forms of penicillin G with penicillin G sodium.
Penicillin G sodium is administered by intramuscular injection or by intravenous injection or infusion.3913 In high doses (i.e., greater than 10 million units), intravenous administration should be performed slowly to avoid electrolyte imbalance from the sodium content.3913
Penicillin G sodium is a white to almost white powder that forms a colorless solution upon reconstitution.3913 Intact vials should be stored at controlled room temperature.3913 The reconstituted solution is stated to be stable for 3 days under refrigeration.3913
The activity of penicillin G 6 mg/L was evaluated in peritoneal dialysis fluids containing dextrose 1.5 and 4.25% (Dianeal 137, Travenol). Storage at 25°C resulted in about a 25% loss of antimicrobial activity in 24 hours. The loss of activity was attributed to the pH (5.2) of the dialysis fluids.515
pH Effects
At 25°C, the maximum stability of penicillin G sodium is attained at pH 6.8,131 but little difference in the rate of decomposition occurs in the pH range of 6.5 to 7.5.1947 Not more than 10% loss occurs in 24 hours in a pH range of 5.4 to 8.5.131 Unbuffered penicillin G sodium injection 12 and 48 mg/mL in sodium chloride 0.9% had an initial pH between 5.4 and 5.8. A 7% loss occurred in 2 days in samples stored at 5°C. However, reconstituting with citrate buffers having pH values of 6.5, 7, and 7.5 resulted in great stability improvement. At these same concentrations in sodium chloride 0.9% in minibags stored at 5°C, losses of 5 to 7% occurred in 28 days and 10% in 56 days.1671
Freezing Solutions
It has been shown that penicillin G sodium in concentrations of 1 to 10%, buffered to pH 6.85, loses not more than 1% in 1 month when frozen at -20°C.99 Another report stated that solutions of penicillin G sodium at a concentration of 50,000 units/mL in water, sodium chloride 0.9%, and 0.05 M citrate buffer and also at a concentration of 500,000 units/mL with sodium citrate 15 mg are stable for at least 12 weeks when frozen at -25°C. At -5°C in the citrate buffer, the rate of decomposition is considerably higher than at either -25 or 5°C.156
Penicillin G sodium 2.5 million units/50 mL of dextrose 5% in PVC containers was physically compatible and stable for 39 days frozen at -20°C. Subsequent thawing and storage at 4°C resulted in a 3 to 4% loss in 10 to 15 days and up to a 10% loss in 31 days.1125
Little penicillin G sodium loss occurred in a solution containing 180,000 units/mL in sterile water for injection in PVC and glass containers after 30 days at -20°C. Subsequent thawing and storage for 4 days at 5°C, followed by 24 hours at 37°C to simulate the use of a portable infusion pump, resulted in about a 12 to 16% penicillin loss.1391
Ambulatory Pumps
The stability of penicillin G sodium 100,000 and 200,000 units/mL in sterile water for injection was evaluated in PVC portable pump reservoirs (Pharmacia Deltec). A 4 to 6% loss occurred in 3 days at 25°C.2080
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