Macrolides

Once absorbed macrolides diffuse well into body fluids, except cerebrospinal fluid, and are concentrated in phagocytes. Excretion is mainly in bile.

Macrolides are active against

• Aerobic and anaerobic gram-positive cocci, except for most enterococci, many Staphylococcus aureus strains (especially methicillin-resistant strains), and some Streptococcus pneumoniae and S. pyogenes strains

• Mycoplasma pneumoniae

• Chlamydia trachomatis

• Chlamydophila pneumoniae

• Legionella species

• Corynebacterium diphtheriae

• Campylobacter species

• Treponema pallidum

• Cutibacterium acnes (formerly Propionibacterium acnes)

• Borrelia burgdorferi

Bacteroides fragilisHaemophilus influenzae and activity against Mycobacterium avium complex.

Macrolides have been considered the drug of choice for group A streptococcal and pneumococcal infections when penicillin cannot be used. However, pneumococci with reduced penicillin sensitivity are often resistant to macrolides, and macrolide resistance among S. pyogenes varies globally. Because they are active against atypical respiratory pathogens, they are often used empirically for lower respiratory tract infections, but another drug is often necessary to cover macrolide-resistant pneumococci. Macrolides have other clinical uses (see table Some Clinical Uses of Macrolides). Macrolides are not used to treat meningitis.

Clostridioides difficile (formerly Clostridium difficile).

Macrolides are contraindicated in patients who have had an allergic reaction to them.

Main concerns with macrolides include

• QT-interval prolongation

• Inhibition of hepatic metabolism, leading to numerous drug interactions