Benzylpenicillin (aka Penicillin G)
[1 vial $1.05]
- Penicillin G, BenPen
- treatment of infections caused by susceptible organisms
PRESENTATION AND ADMINISTRATION:
ICU stocks 600mg (=1 mega unit) vials of Pencillin G Sodium (Novartis). Add 1.6ml of water for injection to each 600mg vial (using 1.6ml of water for injection in a vial will give a concentration of 300mg/ml)
Store at room temperature. Protect from light.
Benzylpenicillin is not stable in glucose and glucose/saline combination IV fluids.
water for injection, normal saline
Administer by either IV injection or intermittent infusion.
To administer by IV injection dilute to 10ml with water for injection and inject slowly at a rate not greater than 300mg/min
To administer by intermittent infusion add to 50-100ml of compatible IV fluid and infuse over 30-60 minutes.
The dry powder is relatively stable and may be stored at room temperature without significant loss of potency. Sterile solutions may be kept in the refrigerator one week without significant loss of potency. Solutions prepared for intravenous infusion are stable at room temperature for at least 24 hours.
Usually in ICU patients higher dose penicillin is preferred. Use 1.2gm-2.4gm Q4-6hrly. In patients with meningitis use 2.4gm 4hrly.
DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:
- Dose in renal impairment [GFR (ml/min)]
<10: 20-50% of normal dose
10-20: 75% of normal dose
>20-50: dose as in normal renal function
- Dose in renal replacement therapy
CAPD: 20-50% of normal dose
HD: 20-50% of normal dose
CVVHDF: 75% of normal dose
DOSAGE IN PAEDIATRICS:
- 30-50 mg/kg 6hrly
- Note that reduced dosage may be required in neonates.
- Penicillin G is bactericidal against penicillin-susceptible microorganisms during the stage of active multiplication. It acts by inhibiting biosynthesis of cell-wall mucopeptide.
- It is not active against the penicillinase-producing bacteria, which include many strains of staphylococci.
- Penicillin G is highly active in vitro against:
staphylococci (except penicillinase-producing strains), streptococci (groups A, C, G, H, L, and M) and pneumococci.
- Other organisms susceptible in vitro to penicillin G are:
Neisseria gonorrhoea, Corynebacterium diphtheriae, Bacillus anthracis, Clostridia, Actinomyces bovis, Streptobacillus moniliformis, Listeria monocytogenes, and Leptospira; Treponema pallidum is extremely susceptible.
- Some species of gram-negative bacilli are susceptible to moderate to high concentrations of penicillin G obtained with intravenous administration. These include:
most strains of Escherichia coli; all strains of Proteus mirabilis, Salmonella, and Shigella; Some strains of Enterobacter aerogenes and Alcaligenes faecalis.
- hypersensitivity to any penicillin
Serious and occasional fatal hypersensitivity (anaphylactoid) reactions have been reported in patients on penicillin therapy.
- Pseudomembranous colitis
Pseudomembranous colitis has been reported with nearly all antibacterial agents, including penicillin, and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhoea subsequent to the administration of antibacterial agents.
Penicillin should be used with caution in individuals with histories of significant allergies and/or asthma. Haemolytic anaemia, leukopaenia, thrombocytopaenia, neuropathy, and nephropathy are rarely observed adverse reactions and are usually associated with high intravenous dosage.
High dosage of penicillin G sodium may result in congestive heart failure due to high sodium intake
- Laboratory Tests:
No tests in addition to routine ICU tests are required
- Drug/Laboratory Test Interactions:
IMPORTANT DRUG INTERACTIONS FOR THE ICU
May diminish the therapeutic effect of Penicillins. Methotrexate: Penicillins may decrease the excretion of Methotrexate.
Penicillins may decrease serum concentrations of the active metabolite(s) of Mycophenolate. This effect appears to be the result of impaired enterohepatic recirculation.
May diminish the therapeutic effect of Penicillins.
- Body as a Whole:
Anaphylaxis, serum sickness
- Nervous System:
Coma (high doses), hyperreflexia (high doses), seizures (high doses)
- Digestive System
Pseudomembranous colitis, hepatitis
- Hematological system:
Neutropaenia, haemolytic anaemia (rare, high doses)
- Renal System:
Acute interstitial nephritis (high doses), renal tubular damage (high doses)