Gramicidin is an antibacterial drug that is too lethal to be utilized in the body, so it is used in the skin and eyes and is blended with different antibacterials (neomycin and polymixin B) and furthermore, with corticosteroids.
This drug is a heterogeneous mixture of antibiotic compounds containing linear pentadecapeptides that are chained up to some amino acids. It is active against all bacteria except for Gram-positive bacilli and some Gram-negative organisms such as Neisseria bacteria. Topical application limits its therapeutic uses, and it cannot be administered internally. Since the exterior epidermis is composed of dead cells, applying it to the surface of the skin will not cause harm.
This drug is also one of the three constituents of over-the-counter polysporin ointments and solutions. It is primarily a topical antibiotic. In 1993, a French-born American microbiologist, Rene Dubos, isolated a substance called thyrothricin, thus creating an antibiotic that can be manufactured commercially.
Increasing the permeability of the bacterial cell membrane can result to bactericidal activity of the drug, allowing inorganic monovalent cations to destroy the ion gradient in the cytoplasm and in the extracellular environment, or to some parts that are unprotected.