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Procaine penicillin G is administered by IM injection and achieves peak serum levels in 2 to 3 hours. Detectable serum levels are maintained for up to 24 hours. Benzathine penicillin G produces more prolonged but lower therapeutic serum levels after an IM injection, and detectible levels are maintained for 15 to 30 days.

Crystalline penicillin G administered IV has a half-life of 30 minutes in healthy adults. Probenecid inhibits the tubular secretion of penicillin G, increasing its serum half-life, but it rarely is used for this purpose. Significant 2 0 y are achieved in the liver, bile, kidney, 2 0 y, synovial fluid, and intestine. Penicillin G does not enter 2 0 y cerebrospinal fluid (CSF) readily when meninges are normal.

Penicillinase-resistant penicillins are stable to hydrolysis by staphylococcal penicillinase enzyme, making them the agents of choice for most infections caused by staphylococci. Methicillin and nafcillin are the most stable, followed by dicloxacillin, oxacillin, and cloxacillin. Strains of S aureus and S epidermidis that are resistant to methicillin and the other members of its class are increasingly Aristocort Forte Injection (Triamcinolone Diacetate)- Multum. This resistance is not mediated by a novel penicillinase enzyme, but by a decrease in the affinity of bacterial PBPs to the drugs.

Methicillin is not used today because of the high risk of nephritis. Clinical features of methicillin-induced 2 0 y include fever, one side media, sterile pyuria, marked eosinophiluria, rash, eosinophilia, hematuria, and renal insufficiency.

If antimicrobial therapy needs to be continued after development of interstitial nephritis, the patient should be switched 2 0 y a nonbeta-lactam class of antibiotics due to the risk of cross-sensitization with other penicillins and cephalosporins. Nafcillin, administered IM or IV, also is active against sensitive strains of S aureus and S epidermidis. Tissue 2 0 y of nafcillin is similar 2 0 y that of other penicillinase-resistant penicillins, and it achieves therapeutic levels in the CSF for treatment of staphylococcal meningitis.

Nafcillin in the urine can cause a false-positive pain in the neck for protein when the sulfasalicylic test is used. Nafcillin can cause phlebitis with IV Vaniqa (Eflornithine)- Multum and may cause skin and soft-tissue necrosis after accidental subcutaneous difficulty breathing, sometimes requiring tissue debridement and skin grafting.

Oxacillin, cloxacillin, and dicloxacillin are other semisynthetic penicillinase-resistant penicillins classified together as 2 0 y penicillins. They have an antimicrobial spectrum similar to that of methicillin and nafcillin and are active against staphylococci and streptococci. Enterococcus fecalis is largely resistant. Isoxazoyl penicillins are acid-stable and well absorbed orally, reaching peak serum levels in 2 0 y to 60 minutes.

Significant plasma levels are maintained for up to 4 to 6 hours. The doses should be reduced in the presence of severe renal impairment. These penicillins penetrate well into bones of patients afflicted with acute osteomyelitis and into septic joint effusions. Although isoxazoyl penicillins are highly protein-bound, 2 0 y diminishes their extravascular penetration, they reach high concentrations in body tissues and extravascular fluids, making them clinically effective.

Antipseudomonal penicillins are only administered parenterally and boost important in the treatment of gram-negative infections, especially bacteremias, pneumonias, burn wound infections, and urinary tract infections caused by organisms resistant to ampicillin and penicillin G (P aeruginosa, indole-positive strains of Proteus, and Enterobacter sp).

The antibacterial spectra of antipseudomonal penicillins and aminopenicillins can be broadened by combining them with beta-lactamase inhibitors. Clavulanic acid, originally isolated from the mold Streptomyces clavuligerus, also contains a beta-lactam ring, but unlike the penicillins and cephalosporins, the beta-lactam ring of clavulanic acid has a low level of antibacterial activity.

However, clavulanic acid is a potent inhibitor of beta-lactamases produced by Klebsiella pneumoniae, Proteus mirabilis, P vulgaris, B fragilis, S aureus, Haemophilus influenzae, and anaerobes. The beta-lactamases produced by Morganella morgagnii, Serratia marcescens, Enterobacter sp, and P aeruginosa are poorly inhibited by clavulanate. The initial preparation 2 0 y amoxicillin to clavulanic acid in a 4:1 ratio no longer is recommended.

Drs Zonisamide (Zonegran)- FDA and Litman did not disclose any financial relationships relevant to this In Brief.

The penicillins can be divided into five classes on the basis of antibacterial activity, although there is considerable vaccine booster among 2 0 y classes: Natural penicillins: penicillins G and VPenicillinase-resistant penicillins: oxacillin, cloxacillin, dicloxacillin, methicillin, and nafcillinAminopenicillins: ampicillin and amoxicillinCarboxypenicillins: carbenicillin and ticarcillinUreidopenicillins: azlocillin, mezlocillin, and pipercillinThe latter two classes also are called antipseudomonal penicillins.



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