Tetracycline, effect metabolism

The tetracyclines are a group of antibiotics with the same basic chemical structure they are derivatives of the naphthacene ring system. Compounds of the series differ in the composition of the side chains (Fig. 1). These antibiotics derived from different Streptomyces species show closely related spectra of bacteriostatic properties, with the exception of minocycline, which is very effective against most Staphylococcus strains resistant to other tetracyclines. Absorption, metabolism, and excretion of the different tetracyclines vary, however. After oral application, tetracycline, oxytetracycline, and chlortetracycline are absorbed to a much lesser degree than demethylchlortetracycline, methacycline, or the almost entirely absorbed minocycline. Maximum blood levels are found 2-6 h after oral intake and immediately in the case of intravenous infusion. Half-lives between 8 and 15 h were reported. The tetracyclines diffuse readily across the vascular barrier and are found in various tissues such as the liver, spleen, bone marrow, kidney, skin, and lungs as well as the peritoneal and pericardiac cavities. The tetracyclines are also able to... 

Bismuth Subsalicylate (Pepto-Bismol) [Antidiarrheal/ Adsorbent] [OTC] Uses Indigestion, N, D combo for Rx of H. pylori Infxn Action Antisecretory anti-inflammatory E>o e Adults. 2 tabs or 30 mL PO PRN (max 8 doses/24 h) Feds. 3—6 y 1/3 tab or 5 mL PO PRN (max 8 doses/24 h) 5-9 y 2/3 tab or 10 mL PO PRN (max 8 doses/24 h) 9-72 y 1 tab or 15 mL PO PRN (max 8 doses/24 h) Caution [C, D (3rd tri), -] Avoid w/ renal failure Hx severe GI bleed Contra Influenza or chickenpox (T risk of Reye synd), ASA allergy (see Aspirin) Disp Chew tabs, caplets, Liq, susp SE May turn tongue stools black Interactions T Effects OF ASA, MTX, valproic acid effects OF tetracyclines i effects W/ corticosteroids, probenecid EMS Monitor for hypovolemia and electrolyte disturbances d/t D may darken tongue stool OD Similar to ASA OD V, tinnitus, metabolic acidosis activated charcoal may be effective... 

Mechanism of Action A tetracycline antibacterial that inhibits bacterial protein synthesis by binding to ribosomal receptor sites also inhibits ADH-induced water reabsorption. Therapeutic Effect Bacteriostatic also produces water diuresis. Pharmacokinetics Food and dairy products interfere with absorption. Protein binding 41 %-91%. Metabolized in liver. Excreted in urine. Removed by hemodialysis. Half-life 10-15 hr. 

Pelletier JP, Cloutier JM, Martel-Pelletier J (1989) In vitro effects of tiaprofenic acid, sodium salicylate and hydrocortisone on the proteoglycan metabolism of human osteoarthritic cartilage. J Rheumatol 16 646-655 Steinmeyer J, Daufeldt S, Taiwo YO (1998) Pharmacological effect of tetracyclines on proteoglycanases from interleukin-l-treated articular cartilage. Biochem Pharmacol 55 93-100... 

Antibiotics. Long-term administration of antibiotics could lead to vitamin B6 deficiency, If symptoms of peripheral neuropathy develop (numbness and tingling of the extremities), administer vitamin B6. Sulfasalazine can decrease the absorption of folic acid, and trimethoprim can cause folate deficiency, hence the need to administer folic acid if there is evidence of deficiency. Rifampicin can cause disturbances in vitamin D metabolism and lead to osteomalacia. The absorption of tetracyclines can be reduced by calcium, magnesium, iron and zinc, while this antibiotic could also decrease the absorption of these minerals. This effect is probably least with minocycline and is not confirmed with doxycycline. Doses of minerals and antibiotic should be separated by at least 2 hours. The absorption of quinolones is reduced by cationic and anionic supplements. 

The spectra of bacterial effectiveness of the various tetracyclines are fairly similar. However, metabolism and excretion vary. In general, preference is currently given to drugs that can be given in relatively low doses (not above 1.0 g/day). 

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