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Tetracyclines PowerPoint Presentation

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Description : antibiotics

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Published on : Sep 10, 2021 | Views : 2240 | Downloads : 7

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Slide 1-

Tetracyclines
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Chemical Structure
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Classification on bases of serum half life Short acting; (tetracycline, chlortetracycline, and oxytetracycline), i.e 6-9 hours Intermediate acting; (demeclocycline and methacycline), i.e 12-13 hours Long acting; (minocycline and doxycycline) i.e 18-16hours
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Mechanism of action Tetracycines inhibit bacterial protein synthesis: Inside the cell, tetracyclines bindi reversibly to the 30S subunit of bacterial ribosome blocking the binding of aminoacyl-tRNA to the acceptor site on mRNA-ribosome complex Thus Prevent addition of amino acid to the growing peptide chain
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Mech. of action
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Pharmacokinetics Absorbtion These antibiotics are partially absorbed from the stomach and upper gastrointestinal tract. Food impairs absorption of all tetracyclines except doxycycline and minocycline whose, absorbtion is improved with food. Tetracyclines form insoluble chelates with calcium , magnesium, and other metal ions,
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Distribution Distributed throughout body tissues and fluids in concentrations that reflect the lipid solubility of each individual agent. Minocycline and doxycycline are the most lipid soluble, while oxytetracycline is the least lipid soluble The tetracyclines penetrate the uninflamed meninges and cross the placental barrier.
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Simultaneous administration with milk (calcium), magnesium hydroxide, aluminum hydroxide, or iron will interfere with absorption. Because some of the tetracyclines are not completely absorbed, any drug remaining in the intestine may inhibit sensitive intestinal microorganisms and alter the normal intestinal flora.
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Peak serum levels are reached approximately 2 hours after oral administration; Cerebrospinal fluid (CSF) levels are only one-fourth those of plasma. Serum half-life of different agents
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Serum protien binding ranges from as low as 25-60% of tetraycline to as high as 70-75% of minocycline
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Metabolism The tetracyclines are metabolized in the liver and are concentrated in the bile. Bile concentrations can be up to five times those of the plasma.
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Doxycycline, minocycline, and chlortetracycline are excreted primarily in the feces. The other tetracyclines are eliminated primarily in the urine by glomerular filtration.
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Anti-bacterial spectrum These drugs are broad spectrum bacteriostatic antibiotics Effective against both gram-positive and gram-negative bacteria, including certain anaerobes, Rickettsia, Chlamydia and Mycoplasmas. Tetracyclines are active against Spirochetes, including Borrelia burgdorferi (Lyme disease) and Treponema pallidum (syphilis)
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Clinical uses Cholera Gastric ulcers (H.Pylori) Gonorrhea UTIs Bronchitis Community acquired Pneumonia Acnes Plaque, tularemia and brucellosis (in combination with other antibiotics) Prophylaxis of plasmodium falciparum infection
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Resistance Three type of resistance mechanisms are; Impaired influx or increased efflux by an active transport protein pump Ribosomal protection due to the production of proteins that interfere with tetracycline binding to ribosome Enzyme inactivation efflux
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Adverse effects Hypersensitivity reactions: Drug fever, skin rashes Direct toxicity: GIT: Nausea, vomiting, dirrhea and Intestinal irritation Bony structures and teeth: tetracycline's bound to calcium deposited in newly formed bone or teeth in young children During pregnancy, In fetus causes discoloration (yellow) of teeth and bone deformity and growth inhibition
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Liver: Impair hepatic function, hepatic necrosis at daily dose of 4g or more i.v. Kidney: Renal tubular acidosis and other renal injuries resulting gin nitrogen retention I.V can lead to venous thrombosis i.M produces painful local irritation Photosensitivity: especially demeclocycline Dizziness, vertigo (at high doses above 100 mg)
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Contraindication Hypersensitive individuals Pregnancy Children's under the age of 8 years Not used with milks or food containing Mg, Ca or other metals Renal insufficiency