University:
Michigan State University
Course:
PHM 430 | Human Pharmacology
Academic year:

2023
Views:

165

Pages:

19
Author:

teespagmaxrtf

Vancomycin • A bactericidal drug which acts by inhibiting cell wall synthesis. • Active only against gram-positive particularly staphylococci. bacteria, • Used IV in treating endocarditis caused by methicillin-resistant staphylococci and resistant enterococci. • Also used orally in Pseudomembraneous Colitis caused by Clostridium difficile . Vancomycin • Valuable in severe staphylococcal infections in patients allergic to penicillins and cephalosporins. • Resistance can be caused by changing the permeability to the drug and by decreasing the binding of Vancomycin to receptors. Vancomycin • Unwanted effects include fever, rashes and local phlebitis. • Ototoxicity and nephrotoxicity can occur and hypersensitivity reactions are occasionally encountered. • Vancomycin must be administered in a dilute solution slowly, over at least 60 minutes to avoid an infusion reaction known as the Red Man Syndrome or Red Neck Syndrome. Protein Synthesis Inhibitors ➢ Active against a wide variety of organisms (broad spectrum). ➢ Most are bacteriostatic but a few are bactericidal against certain organisms. ➢ Because of overuse, resistance is common. ❖ Bacterial ribosomes differ in molecular detail from eukaryotic cells, enabling antibiotics to exhibit selective toxicity. ❖ Interfere with the main ribosomal processes: Binding of aminoacyl-tRNA Normal codon:anticodon recognition Transpeptidation Tetracyclines • Tetracycline, Methacycline, minocycline, and Tigecycline. Moxycycline, doxycycline • Bind to both mRNA and the ribosomal 30S subunit where they prevent the binding of aminoacyl-tRNA. • Bacteriostatic. • Wide spectrum of activity and includes some spirochaetes and even some protozoa like amoebae. Clinical Uses of Tetracyclines Mycoplasma and chlamydia infections Brucellosis: usually in combination with an aminoglycoside. Acne Occasionally used in dentistry to treat bacterial infections. Syphilis Tetracyclines • Resistance is common and mainly due to a plasmidmediated energy-dependent efflux pump(typical of the multiple drug resistance type). Mutations in the tetracycline target site are also found. • Usually administered parenterally. orally but can be given • Absorption from the gut is irregular and better in the absence of food, but they are gastric irritants, so usually given after meals. • Since Tetracyclines are chelated by di- and trivalent metal ions, forming insoluble complexes, absorption is decreased in the presence of milk, certain antacids and iron preparations. Tetracyclines • The most Common side-effects are GI disturbances, essentially due to direct irritation and later to modification of gut flora. • Deposit in growing bones and teeth, so caused staining and dental hypoplasia and bone deformities in children. • Phototoxicity: for example, severe sunburn, after exposure to sun or ultra-violet rays. • Contraindicated in children, nursing mothers and pregnant women (may causes hepatotoxicity in pregnant women). Macrolides • • • • Erythromycin Clarithromycin(1 tablet for 14 days) Azithromycin( 1 tablet for 5 days) Telithromycin. • These bind to the 50S ribosomal subunit and inhibit protein synthesis. • Erythromycin is active against Gram-positive bacteria and spirochaetes but not against most Gram-negative organisms( the same spectrum of Penicillins). • Azithromycin is far more active against respiratory infections due to Haemophilus influenzae and E.coli. Clinical Uses of Macrolides • Because antibacterial spectrum is very similar to that of penicillins, they are considered as a very useful substitutes in penicillin-sensitive patients. • Drugs of choice in corynebacterial infections (diphtheria, corynebacterial sepsis); Clarithromycin • Clarithromycin is effective against Mycobacterium avium cellulare which can cause chronic lung disease in elderly or immunologically compromised individuals. • Clarithromycin is an aadjuvant in the treatment of peptic ulcer to eradicate H. pylori ( 1 tablet for 14 days). Azithromycin • Penetrates well into most tissues (except cerebrospinal fluid), with tissue concentrations exceeding serum concentrations by 10- to 100-fold. • Short treatment course, 1 tablet for 5 days. • Slowly released from tissues (tissue half-life of 2–4 days) to produce an elimination half-life approaching 3 days. • Azithromtcin is the drug of choice in respiratory( Community Aquired Pneumonia), neonatal, ocular, or genital chlamydial infections because the spectrum of activity includes pneumococcus, mycoplasma, and legionella. • Azithromycin shows particularly good activity against chlamydial urethritis. Side Effects of Macrolides • Macrolides are administered orally, although they can be given parenterally. • Gastrointestinal disturbances are common side effects, but not serious. The newer agents seem to have less GI effects. • Skin rashes, and fever. • Transient hearing disturbances have been associated with erythromycin, especially at high dosages. • Cholestatic jaundice especially with the estolate form of erythromycin

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