macrolides Flashcards
What are macrolide antibiotics named for?
They possess a macrocyclic lactone usually having 12 to 17 atoms.
What is the source of erythromycin?
Produced by Streptomyces erythreus found in the Philippines.
What type of agents are macrolides?
Bacteriostatic agents.
List the common structural features of macrolides.
- A macrocyclic lactone (12 to 17 atoms)
- A ketone group (C9)
- A neutral sugar linked to amino sugar or lactone ring
- An aminosugar attached to the lactone
- Presence of a dimethyl amino moiety on the sugar residue.
What is desosamine?
A 3-dimethylamino-3,4,6-trideoxy-D-glucose.
What is the antibacterial spectrum of macrolides?
Active against most species of gram-positive bacteria and some gram-negative cocci, especially Neisseria species.
True or False: Macrolides can be used to replace penicillin in allergic patients.
True.
What is the mechanism of action of erythromycin?
Inhibits translocation.
What are the physical properties of macrolides?
- Crystalline powders
- Water insoluble
- Stable in aqueous solutions at or below room temperature
- Unstable in acidic conditions.
What happens to macrolides under acidic conditions?
They undergo intramolecular reactions to form an inactive cyclic ketal.
What strategies are used to improve the acidic stability of erythromycin?
- Addition of hydroxylamine to form oxime (e.g., roxithromycin)
- Alteration of C-6 hydroxyl group (Clarithromycin)
- Introduction of nitrogen atom to form azalides (azithromycin).
How are macrolides administered?
Orally and parenterally (intravenous injections).
What are the adverse effects of erythromycin?
- Abdominal cramps
- Epigastric distress
- Jaundice
- Transient deafness.
What infections is erythromycin used to treat?
- Upper respiratory tract infections
- Mycoplasma pneumonia
- Gonorrhea.
What is erythromycin ethylsuccinate?
A prodrug with more lipophilicity for longer duration of action.
Describe clarithromycin.
A semisynthetic derivative of erythromycin obtained by selective methylation at C-6 position.
What advantages does clarithromycin have over erythromycin?
- Cannot undergo cyclic ketal formation
- Higher blood concentrations
- More lipophilic
- Lower doses with less intervals.
What infections is azithromycin used to treat?
- Urogenital infections caused by N. gonorrhoeae and Chlamydia trachomatis
- Respiratory tract infections.
What type of antibiotic is roxithromycin?
A semi-synthetic 14-membered ring macrolide antibiotic.
What are the uses of roxithromycin?
- Treatment of skin infections
- Treatment of dental infections
- Treatment of genital infections
- Treatment of upper and lower respiratory tract infections.
