Macrocyclic lactone antibiotics

• This family includes 4 subfamilies which are: 1- Macrolide 2- Polyene 3- Other macrocylic lactone

• A group of antibiotics containing a macrocyclic lactone ring linked glycosidically to one or more sugar moieties. These antibiotics are produced by certain species of Streptomyces. They often inhibit protein synthesis by binding to the 50S subunits...

Erythromycin

• It has 14 membered lactones.• It is whitish, fairly yellow crystalline substance• Soluble in water• It is unstable at room temperature.• It is only stable in neutral solutions for weeks

at refrigerators temperature.

Absorption

• Erythromycin base is absorbed in the small intestine, but its activity is reduced due to the action of acid in the stomach.

• It is excreted in bile• It crosses the placental barrier

Antibacterial action

• It inhibits protein synthesis of E.coli.• For the relatively narrow spectrum of

erythromycin it causes less changes in the intestinal flora than expected with broad spectrum antibiotics.

Toxicity:Fever, Skin eruption, gastrointestinal upset, Diarrhoea are among the common toxicity.

Polyene antibiotics

• Amphotericin B is a polygene antifungal drug, often used intravenously because it is poorly absorbed from the intestinal tract.

• It was originally extracted from Streptomyces nodosus, a filamentous bacterium.

• Its name originates from the chemical's amphoteric properties.

• Two amphotericins, Amphotericin A and Amphotericin B are known, but only B is used clinically because it is significantly more active in vivo

• It is used to treat fungal meningities• In this case amphotricin is given intrathecally

through the cerebrospinal fluid.

Side effects

• Amphotericin B is well-known for its severe and potentially lethal side effects.

• Very often a serious acute reaction after the infusion (1 to 3 hours later) is noted consisting of high fever, hypotension, anorexia, nausea, vomiting, headache, drowsiness, generalised weakness.

• This reaction sometimes subsides with later applications

of the drug and may in part be due to histamine liberation.

Nystatin

Antimicrobial Action

• It increases the leakage of intracellular components from sterol-containing mycellium especially sugar and protein components but do not cause lysis of the organism.

Other macrocyclic lactone

• E.g: Boromycin Belong to ionophorous antibiotics

Brefeldin A

• Antifungal• Has cytotoxic properties