Clindamycin

 Clindamycin is a lincosamide antibiotic that exhibits a broad spectrum of activity, primarily against Gram-positive bacteria and anaerobes.

Mechanism of Action

It works by binding to the 50S ribosomal subunit of bacterial ribosomes, inhibiting protein synthesis.

This action is bacteriostatic but can be bactericidal at higher concentrations against certain organisms. It primarily interferes with peptide chain elongation, thereby suppressing bacterial growth.

Pharmacokinetics

• Half-life (t½)
  Approximately 2-3 hours in healthy adults, but it can extend in patients with severe renal or hepatic dysfunction.
• Metabolism
  metabolized in the liver to active and inactive metabolites. The primary pathway involves oxidation by cytochrome P450 enzymes, producing N-demethylclindamycin and clindamycin sulfoxide.
• Excretion
  About 10% of the drug is excreted unchanged in the urine, while the remainder is eliminated in bile and feces.

Side Effects

1. Common Side Effects

1. • Gastrointestinal: Nausea, vomiting, diarrhea, and abdominal pain.
   • Skin: Rash, pruritus.

2. Serious Side Effects

1. • Clostridioides difficile-associated diarrhea (CDAD).
   • Hypersensitivity reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis.
   • Hepatotoxicity.

Drug Interactions

1. Potentiation of Neuromuscular Blockade

1. • Clindamycin may enhance the effects of neuromuscular blocking agents, leading to respiratory depression.

2. CYP450 Interactions

1. • It may interact with drugs metabolized by CYP450 enzymes, such as phenytoin or warfarin.

3. Antagonism:

1. • Should not be co-administered with erythromycin as they antagonize each other.

Usage in Obstetrics and Gynecology

Clindamycin is widely used in the management of infections particularly those involving anaerobic bacteria.

1. Bacterial Vaginosis (BV)

1. • Dose: 300 mg orally twice daily for 7 days or clindamycin cream 2% intravaginally for 7 days.
   • Evidence: Recommended by RCOG, ACOG, and CDC for the treatment of BV during pregnancy to reduce the risk of adverse outcomes such as preterm birth.

2. Pelvic Inflammatory Disease (PID)

1. • Dose: 900 mg IV every 8 hours in combination with gentamicin.
   • Transition to oral therapy (450 mg four times daily) when clinically appropriate.
   • Evidence: Endorsed by ACOG for severe cases of PID requiring hospitalization.

3. Postpartum Endometritis

1. • Dose: 900 mg IV every 8 hours, often in combination with gentamicin.
   • Evidence: Supported by TOG guidelines for treating polymicrobial infections in post-cesarean endometritis.

4. Group B Streptococcus (GBS) Prophylaxis

1. • Indicated in penicillin-allergic patients at high risk for anaphylaxis, provided the organism is susceptible.
   • Dose: 900 mg IV every 8 hours during labor.
   • Evidence: ACOG guidelines support its use in cases of confirmed susceptibility to clindamycin.

5. Surgical Prophylaxis

1. • Used in combination with gentamicin or cefazolin for cesarean section prophylaxis in penicillin-allergic patients.
   • Dose: 900 mg IV as a single dose preoperatively.
   • Evidence: Included in RCOG and ACOG recommendations for alternative antibiotic prophylaxis.

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