PHA3801 Lecture Notes - Lecture 5: Gingivitis, Cyp3A4, Inflammatory Bowel Disease
24 Jul 2018
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Mechanism: binds to 30s ribosomes, prevents attachment of aminoacyl trna to mrna ribosomal complex. Stops synthesis of peptide chain no protein produced. Broad spectrum: gram+/- aerobes + anaerobes, limited by development of resistance. Entry into bacterial cell: drugs enter cells by porons (gram-) or passive diffusion (gram+). Protein carrier system transports from periplasmic space inside cytosplasm membrane. Resistance: commonly involves efflux by a transporter system induced by drug. Mutations can also alter the outer membrane proteins, plasmid generated protein can compete for drug at 30s binding site. Half life: for short acting tc"s (tetracycline, oxytetracycline = 8-10hours), long acting like doxycyclin (= 18-22hours). Absorption: from gut is incomplete (exception = doxycycline) Do not pass bbb (cannot tx e. g. meningitis). Adverse reactions: git disturbances (adr common to many abs) caused by direct irritation and later by modification of gut flora, staining of teeth, dental hypoplasia and bone deformities, phototoxicity, allergic reactions are rare, liver toxic when high fosse.
