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Sulfonamides can be divided into three major groups: (1) oral, absorbable; (2) oral, nonabsorbable; and (3) topical. The oral, absorbable sulfonamides can be classified as short-, medium-, or long acting on the basis of their half-lives. Mechanisms of action: Microorganisms require extracellular para-aminobenzoic acid (PABA) to form dihydrofolic acid, an essential step in the production…

Rifampin binds strongly to the bacterial DNA-dependent RNA polymerase and thereby inhibits RNA synthesis. It is well absorbed after oral administration and excreted mainly through the liver into bile. Rifampin is distributed widely in body fluids and tissues. It is relatively highly protein- bound, and so adequate cerebrospinal fluid concentrations are achieved only in the…

Quinolones are synthetic fluorinated analogs of nalidixic acid, that nucleic acid synthesis. Ofloxacin and ciprofloxacin inhibit gram-negative cocci and bacilli, including Enterobacteriaceae, Pseudomonas, Neisseria, Haemophilus, and Campylobacter. Many staphylococci also are sensitive these drugs. Intracellular pathogens such as Legionella, Chlamydia, M tuberculosis and M avium complex, are inhibited by fluoroquinolones. Pharmacokinetics: After oral administration, the…

Nalidixic acid is the first antibacterial quinolone. It is not fluorinated and is excreted too rapidly to have systemic antibacterial effects. They inhibit normal transcription and replication of bacterial DNA. Because of their relatively weak antibacterial activity, these agents were useful only for the treatment of urinary tract infections and shigellosis.

Spectinomycin is an aminocyclitol antibiotic that is structurally related to aminoglycosides. Spectinomycin is used almost solely as an alternative treatment for gonorrhea in patients who are allergic to penicillin or whose gonococci are resistant to other drugs. It is rapidly absorbed after intramuscular injection. A single dose of 2 g (40 mg/kg) is given. There…

These drugs are closely related is also a member of this group. All have similar properties. Neomycin and kanamycin are too toxic for parenteral use and are now limited to topical and oral use. Neomycin is given orally in preparation for elective bowel surgery. In hepatic coma, the coliform flora can be suppressed for prolonged…

Amikacin is a semisynthetic derivative of kanamycin; it is less toxic than the parent molecule. It is resistant to many enzymes that inactivate gentamicin and tobramycin, and it therefore can be employed against some microorganisms resistant to the latter drugs. Strains of multidrug- resistant Mycobacterium tuberculosis, including streptomycin-resistant strains, are usually susceptible to amikacin.

Gentamicin inhibits many strains of staphylococci and coliforms and other gram-negative bacteria. It is a synergistic companion with beta-lactam antibiotics, against Pseudomonas, Proteus, Enterobacter, Klebsiella, Serratia, Stenotrophomonas, and other gram-negative rods that may be resistant to multiple other antibiotics. Gentamicin is also used concurrently with penicillin G for bactericidal activity in endocarditis due to viridans…

Streptomycin is mainly used as a first-line agent for treatment of tuberculosis. Adverse Reactions: Disturbance of vestibular function (vertigo, loss of balance) is common. The frequency and severity of this disturbance are proportionate to the age of the patient, the blood levels of the drug, and the duration of administration. Vestibular dysfunction may follow a…

Members: Streptomycin, neomycin, kanamycin, amikacin, gentamicin, netilmicin. Pharmacokinetics: Aminoglycosides are absorbed very poorly from the intact gastrointestinal tract. After intramuscular injection, aminoglycosides are well absorbed. They are highly polar compounds that do not enter cells readily. The kidney clears aminoglycosides, and excretion is directly proportionate to creatinine clearance. Adverse effects: Aminoglycosides damage the VIII nerve…