indication

For treatment of skin lesions, surface wounds and eye infections

pharmacology

Gramicidin is particularly effective against gram-positive bacteria. Because the drug is highly hemolytic, it cannot be administered internally and so is used only on the skin as a lotion or ointment. It is used primarily in the treatment of infected surface wounds, and in eye, nose, and throat infections. It is normally given with two other antibiotics (neomycin and polymixin B) as an ophthalmic solution

mechanism of action

Gramicidin D binds to and inserts itself into bacterial membranes (with a strong preference to gram-positive cell membranes). This results in membrane disruption and permeabilization (it acts as a channel). This leads to (i) loss of intracellular solutes (e.g., K+ and amino acids); (ii) dissipation of the transmembrane potential; (iii) inhibition of respiration; (iv) a reduction in ATP pools; and (v) inhibition of DNA, RNA, and protein synthesis, which leads to cell death.