Macrolides

Macrolides:
Group of related compounds that are characterised by a macrocyclic lactone ring(14 or 16 atoms) that deoxy sugars attach to.

Erythromycin*:
• produced by Streptomyces erythraeus
• binds to 50S subunit of bacterial ribosomes  interferes with protein synthesis by blocking addition of new amino acids to growing peptide chain
• effective against a wide range of organisms; enhanced activity in alkaline pH
• acid-sensitive  buffered or have enteric coating to protect from gastric acids
• well absorbed orally, but food can interfere with it
• resistance can develop by three mechanisms – reduced permeability of cell membrane; production of esterases that can hydrolyse macrolides; modification of the ribosomal binding site by a chromosomal mutation
• destroyed by stomach acid  administered with enteric coating; food can interfere with absorption
• eg EES®, EMU-v®, E-mycin®, Eryc®, Erythrocin®,
• used if allergic to penicillins, but some cross-sensitivity can occur
• well absorbed from GI tract and widely distributed in body, except for cerebrospinal fluid; primarily eliminated by liver
• adverse effects – GI disturbances (anorexia, nausea, vomiting, diarrhoea); liver injury (hepatitis)

Roxithromycin*
• Biaxsig®, Rulide®,

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