#principen

Common Brand Names: Principen

Therapeutic Class: A semi-synthetic aminopenicillin antibiotic

Common Injectable Dosage Forms:

Powder for Injection: In vials and piggybacks in 125 mg, 250 mg, 500 mg, 1 gram, and 2 grams. Also available in 10-gram bulk vials.

Dosage Ranges:

For GI infections, URIs, skin and skin structure infections: Adults: 500-1000 mg IV/IM every 6 hours, may increase up to 14 g/day. Children <20 kg and infants: 100-200 mg/kg/day IV/IM in equal doses every 4-6 hours; neonates 5-100 mg/kg/day IV/IM every 6-12 hours.

Severe infections, including those of bone, meningitis, pneumonia: Adults and children >20 kg 150-200 mg/kg/day IV/IM in equal doses every 3-4 hours. Max daily dosage 14 g/day. Children <20 kg and infants: 100-200 mg/kg/day in divided doses every 4-6 hours, max of 12 g/day. Neonates: 50-100 mg/kg/day every 6-12 hours.

Prophylaxis of group B streptococci in neonates: Give mother 2 g IV ~4 hours before delivery, then 1-2 g IV every 4-6 hours until delivery.

Bacterial endocarditis prophylaxis: 2 g IV/IM, 30 minutes before procedure.

Administration and Stability: The drug should be reconstituted with a small volume of sterile water for IM injection, and given deeply into a large muscle. For direct IV injection, the drug should be given over 10-15 minutes to avoid precipitation of seizures (do not exceed 100 mg/min). When given by intermittent IV infusion the frug should be diluted with 50-100 mL of compatible solution (NS, not D5W, maximum concentration of 30 mg/mL) and infused over 15-30 minutes. Stability of vials (100 mg/mL) is 1 hour at room temperature. When further diluted with NS for administration stability is 8 hours at room temperature and 72 hours when refrigerated. DO NOT FREEZE! pH of 10 mg/mL solution: 8-10

Pharmacology/Pharmacokinetics: Penicillins act by inhibiting bacterial wall synthesis via acylation of the transpeptidase enzyme. Ampicillin is active against gram-positive bacteria, including S. aureus, pneumococcus, beta-hemolytic streptococcus and alpha streptococcus. It is also active against gram-negative bacteria including Haemophilus influenzae, E. coli, and Enterobacteriaceae. It is inactivated by penicillinase-producing organisms. Peak concentration occurs in 1 hour after an IM dose. Up to 15-25% is bound to plasma proteins. Distribution to the meninges occurs during inflammation. Excreted predominantly (40%) in the urine as unchanged drug. Elimination half-life is 1-1.5 hours.

Drug and Lab Interactions: May inactivate aminoglycosides when mixed in the same solution. Chloramphenicol may antagonize antibacterial activity. Ampicillin may also decrease the effectiveness of oral contraceptives. Probenecid inhibits renal tubular secretion of ampicillin, causing higher, prolonged serum concentrations. May cause false-positive urine glucose tests if Clinitest, Benedict’s Solution, or Fehling’s Solution is used. Also causes false-positive Coomb’s test, serum uric acid test using copper-chelate methods, and urinary protein determinations.

Contraindications/Precautions: Contraindicated in patients hypersensitive to penicillins and/or cephalosporins and in renal impairment or renal disease. Relatively contraindicated in those with viral disease, lymphatic leukemia, CMV, and especially mononucleosis because these patients have a higher incidence of rashes. Use bacteriologic studies to determine optimum therapy. Use caution when given by the IV route due to the possibility of thrombophlebitis. Examine solutions prior to administration and discard if discolored or cloudy. As with all antibiotics, the possibility of superinfections should be considered. Pregnancy Category B.

Monitoring Parameters: BUN, Serum creatinine.

Adverse Effects: If hypersensitivity occur, manifested by urticaria, edema, laryngospasm, bronchospasm, or hypotension, discontinue use and institute supportive treatment. As with all antibiotics, the possibility of bacterial and fungal overgrowth should be considered. Severe diarrhea may be a sign of pseudomembranous colitis and warrants immediate attention. IM use may cause skin rash, pruritus, and drug fever.