Usage
Procaine Penicillin G is an antibiotic belonging to the penicillin class. It is primarily used for treating moderately severe infections caused by penicillin-G-susceptible microorganisms. These infections often require low and persistent serum levels of penicillin. Specific infections for which Procaine Penicillin G is indicated include: streptococcal infections (Groups A, C, G, H, L, and M), some staphylococcal infections, fusospirochetosis (caused by fusiform bacilli and spirochetes), diphtheria (in conjunction with antitoxin), syphilis (all stages), yaws, bejel, pinta, anthrax, and rat-bite fever. It is important to note that Procaine Penicillin G is not recommended for the initial treatment of severe pneumococcal infections or for prophylaxis against bacterial endocarditis. For those conditions, other forms of penicillin are preferred.
Its pharmacological classification is beta-lactam antibiotic.
The mechanism of action of Procaine Penicillin G involves inhibiting bacterial cell wall synthesis by binding to and inactivating penicillin-binding proteins (PBPs). This weakens the bacterial cell wall, leading to cell lysis and death.
Alternate Names
Procaine Penicillin G is also known as APPG, Benzylpenicillin Procaine, and Procaine Benzylpenicillin. Brand names include Duracillin A-S, Pfizerpen A-S, Wycillin, and Crysticillin. Bicillin C-R contains Procaine Penicillin G combined with Penicillin G Benzathine.
How It Works
Pharmacodynamics: Procaine Penicillin G exerts its bactericidal effect by disrupting the synthesis of the peptidoglycan layer of bacterial cell walls. This leads to cell wall instability and eventual lysis of the bacteria.
Pharmacokinetics:
- Absorption: Administered intramuscularly (IM), Procaine Penicillin G is absorbed slowly, achieving peak serum concentrations within 12–24 hours post-injection. The procaine component provides a slow, sustained release of penicillin into the bloodstream.
- Metabolism: Procaine Penicillin G is metabolized to penicillin G and procaine.
- Elimination: Penicillin G is primarily eliminated by the kidneys via glomerular filtration and tubular secretion. Probenecid can compete with penicillin for tubular secretion, thereby increasing penicillin’s serum half-life. Procaine is metabolized by plasma esterases and also excreted renally.
Mode of Action: Procaine Penicillin G inhibits bacterial cell wall synthesis by irreversibly binding to and inactivating PBPs. This disrupts the cross-linking of peptidoglycan strands, leading to a weakened cell wall and bacterial death.
Receptor binding, enzyme inhibition, or neurotransmitter modulation: The primary mechanism is the inhibition of PBPs, which are bacterial enzymes crucial for cell wall synthesis.
Elimination pathways: Primarily renal excretion.
Dosage
Procaine Penicillin G is administered intramuscularly (IM) only. It should not be administered intravenously (IV), subcutaneously (SC), or intrathecally (IT). Dosage depends on the infection being treated and patient factors.
Standard Dosage
Adults:
- The usual adult dose ranges from 600,000 to 1,200,000 units IM once or twice daily. For syphilis, 600,000 units IM daily is common.
Children:
- Dosing for children varies according to age and weight: For infants under 2 kg: 50,000 units/kg IM once daily. For children between 2 kg and 27 kg: 300,000 units IM once daily for 10-14 days or 25,000-50,000 units/kg/day IM divided every 12-24 hours. For children over 27 kg: 600,000 to 1,200,000 units IM once daily. For children aged 1 month or older: 50,000 units/kg/day IM divided into one or two doses (maximum 1.2 million units/day) for 14 days.
Special Cases:
- Elderly Patients: Age-related renal impairment may necessitate dosage adjustments. Monitoring renal function is recommended.
- Patients with Renal Impairment: Dosage adjustment is essential for patients with creatinine clearance less than 10 mL/min/1.73m². A full loading dose followed by half the loading dose every 8–10 hours is a common adjustment. For patients with creatinine clearance greater than 10 mL/min/1.73m², a full loading dose followed by half the loading dose every 4–5 hours is often used.
- Patients with Hepatic Dysfunction: No specific dosage adjustments for hepatic dysfunction are typically required.
- Patients with Comorbid Conditions: Consider comorbidities, especially allergies and asthma.
Clinical Use Cases
Dosages for the listed clinical use cases are not specifically defined for Procaine Penicillin G but may be within the general range. Consult specialized literature and guidelines for appropriate antibiotic use in these settings. Procaine Penicillin G is usually not the first-line treatment choice for severe or acute infections, particularly in intensive care or emergency situations.
- Intubation: Not typically indicated.
- Surgical Procedures: Not typically indicated for prophylaxis.
- Mechanical Ventilation: Not typically indicated.
- Intensive Care Unit (ICU) Use: Not typically the preferred penicillin for ICU settings.
- Emergency Situations: Not typically indicated.
Dosage Adjustments
Dosage modifications are needed for renal impairment (see above). Consider adjustments for other conditions based on patient-specific factors.
Side Effects
Common Side Effects
Nausea, vomiting, pain, swelling, or bruising at the injection site, diarrhea, dizziness, headache, drowsiness.
Rare but Serious Side Effects
Allergic reactions (rash, hives, itching, difficulty breathing or swallowing, swelling of the face, throat, or tongue), severe diarrhea, neurovascular damage (if injected near a nerve or artery), seizures, hallucinations, cardiac effects. Methemoglobinemia (cyanosis, abnormal blood coloration), serum sickness (fever, joint pain, rash).
Long-Term Effects
With prolonged use: low white blood cell count, serum sickness.
Adverse Drug Reactions (ADR)
Anaphylaxis (requiring immediate medical attention), Jarisch-Herxheimer reaction (when treating syphilis).
Contraindications
Hypersensitivity to penicillin or procaine.
Drug Interactions
Tetracyclines (antagonistic effect), Probenecid (increased penicillin levels), some other antibiotics (e.g., aminosalicylic acid), anticoagulants (potential increased bleeding risk), oral contraceptives (efficacy may be reduced). See a drug interaction database for a complete list of interactions.
Pregnancy and Breastfeeding
Pregnancy Safety Category (old FDA classification): Not assigned (new system in place), previously Category B. Generally considered safe to use during pregnancy but should only be used if clearly needed.
Drug excretion in breast milk is minimal and generally considered safe for breastfeeding. Monitor infant for signs of thrush or diarrhea.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial cell wall synthesis by binding to PBPs.
- Side Effects: Common: Nausea, vomiting, injection site reactions. Serious: Allergic reactions, neurovascular damage, methemoglobinemia, serum sickness.
- Contraindications: Hypersensitivity to penicillin or procaine.
- Drug Interactions: Tetracyclines, Probenecid, others (see detailed section).
- Pregnancy & Breastfeeding: Generally considered safe; monitor for adverse effects in infants.
- Dosage: IM administration only; varies with age, condition, and renal function.
- Monitoring Parameters: Renal function during prolonged use, signs of allergic reaction.
Popular Combinations
Procaine Penicillin G is combined with Penicillin G Benzathine (e.g., Bicillin C-R) for an extended duration of action.
Precautions
Perform skin testing for penicillin allergy before administering, especially in patients with a history of allergies or asthma. Caution with renal impairment. Inject deep IM only; avoid nerves and arteries. Monitor for methemoglobinemia, especially with concomitant use of oxidizing agents. Closely monitor patients with G6PD deficiency.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Procaine Penicillin G?
A: The dosage depends on the infection being treated, the patient’s age, weight, and renal function. Refer to the detailed dosage section above.
Q2: Can Procaine Penicillin G be given intravenously?
A: No, Procaine Penicillin G is for IM administration only. IV administration can cause serious adverse reactions, including neurovascular damage.
Q3: What are the signs of an allergic reaction to Procaine Penicillin G?
A: Allergic reactions can range from mild skin rashes to severe anaphylaxis. Signs include rash, hives, itching, difficulty breathing, swelling of face/throat/tongue, and a drop in blood pressure. Seek immediate medical attention if these occur.
Q4: How is Procaine Penicillin G different from other penicillins?
A: Procaine Penicillin G is formulated with procaine for slow, sustained release. This creates lower but more persistent serum penicillin levels compared to aqueous penicillin G, which is given IV or IM for rapid, high serum levels.
Q5: Can Procaine Penicillin G be used to treat gonorrhea?
A: No, it’s not recommended for gonorrhea due to the prevalence of resistant strains.
Q6: What are the potential drug interactions with Procaine Penicillin G?
A: Significant interactions occur with tetracyclines, probenecid, and certain other medications. Consult a drug interaction database for a comprehensive list.
Q7: What is methemoglobinemia, and how does it relate to Procaine Penicillin G?
A: Methemoglobinemia is a blood disorder where the blood’s capacity to carry oxygen is reduced. Procaine in Procaine Penicillin G can increase the risk of this, particularly in patients with certain enzyme deficiencies (G6PD deficiency). Signs include cyanosis and changes in blood color.
Q8: What are the precautions for using Procaine Penicillin G during pregnancy and breastfeeding?
A: It’s generally considered safe but should only be used if clearly needed during pregnancy. In breastfeeding, monitor the infant for potential side effects like thrush or diarrhea.
Q9: What should be done if a dose of Procaine Penicillin G is missed?
A: Contact your doctor as soon as possible to reschedule the injection.
Q10: Is Procaine Penicillin G effective against viral infections?
A: No, Procaine Penicillin G, like all antibiotics, is only effective against bacterial infections. It does not treat viral infections such as the flu or common cold.
