Penicillins

See also the following individual entries:

Amoxicillin

Amoxicillin and Potassium clavulanate Ampicillin oral

Ampicillin sodium/Sulbactam sodium Cloxacillin sodium Penicillin G benzathine, parenteral Penicillin V potassium Action/Kinetics: The bactericidal action of penicillins depends on their ability to bind penicillin-binding proteins (PBP-1 and PBP-3) in the cytoplasmic membranes of bacteria, thus inhibiting cell wall synthesis. Some penicillins act by acylation of membrane-bound transpeptidase enzymes, thereby preventing cross-linkage of peptidoglycan chains, which are necessary for bacterial cell wall strength and rigidity. Cell division and growth are inhibited and often lysis and elongation of susceptible bacteria occur. Penicillin is most effective against young, rapidly dividing organisms and has little effect on mature resting cells. Depending on the concentration of the drug at the site of infection and the susceptibility of the infectious microorganism, penicillin is either bacteriostatic or bactericidal. Penicillins are distributed throughout most of the body and pass the pla-cental barrier. They also pass into synovial, pleural, pericardial, peritoneal, ascitic, and spinal fluids. Although normal meninges and the eyes are relatively impermeable to penicillins, they are better absorbed by inflamed meninges and eyes. Peak serum levels, after PO: 1 hr. ty2: 30—110 min; protein binding: 20%—98% (see individual agents). Excreted largely unchanged by the urine as a result of glomerular filtration and active tubular secretion.

Uses: See individual drugs. Effective against a variety of gram-positive, gram-negative, and anaerobic organisms.

Contraindications: Hypersensitiv-ity to penicillins, imipenem, and ce-phalosporins. PO use of penicillins during the acute stages of empyema, bacteremia, pneumonia, meningitis, pericarditis, and purulent or septic arthritis.

Special Concerns: Use of penicillins during lactation may lead to sen-sitization, diarrhea, candidiasis, and skin rash in the infant. Use with caution in clients with a history of asthma, hay fever, or urticaria. Clients with cystic fibrosis have a higher incidence of side effects with broad spectrum penicillins. Safety and effectiveness of the beta-lactamase inhibitor/penicillin combinations (e.g., amoxicillin/potassium clavulanate, ticarcillin/ potassium clavulanate) have not been determined in children less than 12 years of age. The incidence of resistant strains of staphy-lococci to penicillinase-resistant penicillins is increasing. Use of prolonged therapy may lead to superinfection (i.e., bacterial or fungal overgrowth of nonsusceptible organisms).

Side Effects: Penicillins are potent sensitizing agents; it is estimated that up to 10% of the US population is allergic to the antibiotic. Hypersensitiv-ity reactions are reported to be on the increase in pediatric populations. Sensitivity reactions may be immediate (within 20 min) or delayed (as long as several days or weeks after initiation of therapy). Allergic: Skin rashes (including maculopapular and exanthematous), exfoliative dermatitis, erythema multiforme (rarely, Stevens-Johnson syndrome), hives, pruritus, wheezing, anaphylaxis, fever, eosinophilia, angioedema, serum sickness, laryngeal edema, laryngos-pasm, prostration, angioneurotic edema, bronchospasm, hypotension, vascular collapse, death. Oral: Bitter/unpleasant taste, glossitis, gastritis, stomatitis, dry mouth, sore mouth or tongue, furry tongue, black "hairy" tongue. GI: Diarrhea (may be severe), abdominal cramps or pain, N&V, bloating, flatulence, increased thirst, bloody diarrhea, rectal bleeding, enterocolitis, pseudomembranous colitis. CNS: Dizziness, insomnia, hy-peractivity, fatigue, prolonged muscle relaxation. Neurotoxicity including lethargy, neuromuscular irritability, seizures, hallucinations following large IV doses (especially in clients with renal failure). Hematologic: Thrombocytopenia, leukopenia, ag-ranulocytosis, anemia, thrombocyto-penic purpura, hemolytic anemia, granulocytopenia, neutropenia, bone marrow depression. Renal: Ol-iguria, hematuria, hyaline casts, pro-teinuria, pyuria (all symptoms of interstitial nephritis), nephropathy. Electrolyte imbalance following IV use. Miscellaneous: Hepatotoxicity (cholestatic jaundice), superinfection, swelling of face and ankles, anorexia, hyperthermia, transient hepatitis, vaginitis, itchy eyes. IM injection may cause pain and induration at the injection site, ecchymosis, and hematomas. IV use may cause vein irritation, deep vein thrombosis, and thrombophlebitis. Drug Interactions Antacids / i Effect of penicillins due to i absorption from GI tract Antibiotics, Chloramphenicol, Erythromycins, Tetracyclines / i Effect of penicillins

Anticoagulants / Penicillins may potentiate pharmacologic effect Aspirin / T Effect of penicillins by i plasma protein binding Chloramphenicol / Either T or i effects

Erythromycins / Either T or i effects

Heparin / T Risk of bleeding following parenteral penicillins Oral contraceptives / i Effect of oral contraceptives Phenylbutazone / T Effect of penicillins by i plasma protein binding

Tetracyclines / i Effect of penicillins

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