Fusidic acid

Fusidic acid is an antibiotic that belongs to a class of medications known as fusidanes. It is primarily used to treat bacterial infections caused by susceptible organisms, particularly those involving the skin, such as impetigo, folliculitis, and cellulitis. Fusidic acid works by inhibiting bacterial protein synthesis, thereby stopping the growth and multiplication of bacteria.

Mechanism of Action

Fusidic acid exerts its antibacterial effect by binding to the elongation factor G (EF-G) in bacterial cells. This binding interferes with the translocation step in protein synthesis, a critical phase in the bacterial ribosomal cycle. As a result, the synthesis of bacterial proteins is halted, leading to the inhibition of bacterial growth and replication.

Pharmacokinetics

After oral administration, fusidic acid is well absorbed from the gastrointestinal tract. It exhibits a high degree of protein binding and has a relatively long half-life, which allows for dosing intervals of typically twice or thrice a day. Fusidic acid is metabolized in the liver and excreted in bile and, to a lesser extent, in urine.

Clinical Uses

Fusidic acid is used to treat a variety of skin infections caused by Gram-positive bacteria, including Staphylococcus aureus and Streptococcus spp. It is effective against methicillin-resistant Staphylococcus aureus (MRSA) strains, making it a valuable option in treating infections caused by these resistant bacteria. In addition to skin infections, fusidic acid is also used in the treatment of osteomyelitis, pneumonia, and septic arthritis when caused by susceptible strains of bacteria.

Side Effects

The most common side effects of fusidic acid include gastrointestinal disturbances such as nausea, vomiting, and diarrhea. Liver enzyme elevations may occur, and therefore, monitoring of liver function tests is recommended during prolonged therapy. Allergic reactions, although rare, can also occur.

Resistance

The emergence of bacterial resistance to fusidic acid has been reported, particularly with prolonged use. Resistance mechanisms include mutations in the EF-G gene and the development of efflux pumps that reduce drug concentration within bacterial cells. To minimize resistance development, fusidic acid should be used judiciously and, when possible, in combination with other antibiotics.

Formulations

Fusidic acid is available in various formulations, including creams, ointments, eye drops, and oral forms (tablets and suspensions). The choice of formulation depends on the location and severity of the infection.

Conclusion

Fusidic acid is a valuable antibiotic in the treatment of skin infections and other infections caused by susceptible Gram-positive bacteria. Its unique mechanism of action and efficacy against MRSA make it an important option in the antibiotic arsenal. However, the potential for resistance development necessitates careful use of this medication.