Antibacterial drugs

Approximately 90-100% of an oral dose of doxycycline hyclate is absorbed from the GI tract in fasting adults. Following oral administration of capsules containing doxycycline hyclate in fasting adults with normal renal function, peak serum concentrations of doxycycline are attained within 1.5-4 hours and average 1.5-2.1 mcg/mL following a single 100-mg dose and 2.6-3 mcg/mL following a single 200-mg dose.

Doxycycline calcium, doxycycline hyclate, and doxycycline monohydrate are administered orally. When oral therapy is not feasible, doxycycline hyclate may be administered by slow IV infusion; however, oral therapy should replace IV therapy as soon as possible.

Tetracyclines, in appropriate dosage forms, are administered orally, IV, or by deep IM injection. IV or IM administration should be used only when the oral route is not feasible, and oral therapy should replace parenteral therapy as soon as possible. IM administration of tetracyclines is rarely indicated because this route of administration is painful and, in the usual dosage, produces lower serum concentrations than does oral administration. If the drugs are given IV, the risk of thrombophlebitis should be considered.

The most frequent adverse reactions to tetracyclines are dose-related GI effects including nausea, vomiting, diarrhea, bulky loose stools, anorexia, flatulence, abdominal discomfort, and epigastric burning and distress. Stomatitis, glossitis, dysphagia, sore throat, hoarseness, black hairy tongue, pancreatitis, and inflammatory lesions in the anogenital region with candidal overgrowth have also been reported occasionally.

Tetracyclines are used principally in the treatment of infections caused by susceptible Rickettsia, Chlamydia, Mycoplasma, and a variety of uncommon gram-negative and gram-positive bacteria.

Sulfisoxazole and its derivatives share the actions and uses of the sulfonamides. The relative solubility of the drug in alkaline and slightly acidic urine makes the drug particularly useful for the treatment of urinary tract infections. A combination product containing sulfisoxazole acetyl and erythromycin ethylsuccinate is commercially available for the treatment of acute otitis media caused by susceptible strains of Haemophilus influenzae in children and is usually active against ampicillin-resistant strains of the organism.

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Generally, the incidence of severe sulfasalazine-induced adverse effects is low, but minor adverse effects occur frequently. Onset of adverse effects generally occurs within a few days to 12 weeks following initiation of sulfasalazine therapy, especially when dosage exceeds 4 g daily. Clinical experience to date indicates that the incidence of sulfasalazine-induced adverse effects in patients with ulcerative colitis generally is similar to that reported in patients with rheumatoid arthritis, although there is a greater incidence of some reactions. The most frequent adverse effects associated with sulfasalazine therapy in patients with ulcerative colitis are anorexia, headache, nausea, vomiting, gastric distress, and reversible oligospermia.

Sulfasalazine conventional and delayed-release tablets are administered orally. The total daily dosage should be divided into equally divided doses, and, if possible, doses should be administered after meals. The delayed-release tablets should be swallowed whole. For the treatment of ulcerative colitis, the interval between doses of sulfasalazine given as conventional or delayed-release tablets should not exceed 8 hours.

Sulfamethizole shares the actions and uses of the other antibacterial sulfonamides. Sulfamethizole is used principally in the treatment of urinary tract infections caused by sulfonamide-susceptible organisms.