Gramicidin

Ophthalmic: 0.025 mg/mL (1-2 drops) or thin layer of ointment

Standard ophthalmic dosing for mild bacterial conjunctivitis. Apply 1-2 drops of gramicidin-containing ophthalmic solution (Neosporin Ophthalmic: gramicidin 0.025 mg/mL + neomycin 1.75 mg/mL + polymyxin B 10,000 units/mL) to the affected eye. Or apply thin ribbon of ophthalmic ointment to the lower conjunctival sac. Topical skin use: apply thin layer of triple antibiotic ointment to clean wound.

Ophthalmic: 0.025 mg/mL (1-2 drops); Topical: thin layer of ointment

Standard treatment course for bacterial conjunctivitis and moderate superficial infections. Ophthalmic: apply every 4-6 hours while awake. For topical wound care: clean wound, apply thin layer of gramicidin-containing antibiotic ointment, cover with sterile bandage. Do not use for longer than 10 days without medical reassessment. Available over-the-counter in most topical antibiotic preparations.

Research use: 1-50 µg/mL in electrophysiology or antimicrobial assays

Research applications for ion channel biophysics, single-channel electrophysiology, antimicrobial susceptibility testing, or anticancer activity evaluation. Gramicidin is dissolved in methanol, ethanol, or DMSO stock solutions (typically 1-10 mg/mL) and diluted to working concentrations. For planar lipid bilayer experiments, picomolar to nanomolar concentrations are sufficient for single-channel recordings. For anticancer research, working concentrations of 1-50 µg/mL.

Gramicidin is a cyclic peptide antibiotic derived from Bacillus brevis with a 70+ year track record of topical safety. It functions as a pore-former in bacterial membranes and shows minimal systemic absorption when applied to intact skin or mucous membranes, making it extremely low-toxicity for localized use. The primary safety concern is sensitization reactions in 1-5% of users with prolonged exposure, not organ toxicity. Gramicidin is FDA-approved for topical antibacterial applications and generally well-tolerated across age groups.

Gramicidin safety derives from extensive clinical use since 1940s as a topical antibiotic in wound care and oral preparations, with minimal adverse event reporting. In vitro studies confirm rapid bacterial cell death via ion channel disruption without mammalian toxicity at therapeutic concentrations. Contact dermatitis and allergic sensitization are the documented safety signals, not systemic toxicity. FDA oversight and decades of post-marketing surveillance support its continued use in medical devices and antimicrobial formulations.

Experienced by some users

• •Superinfection

These typically resolve with continued use or dose adjustment.

Common reasons

• •Not at therapeutic dose yet—initial doses are for building tolerance, not maximum effect
• •Insufficient time at target dose—most compounds need several weeks to show full benefits
• •Inconsistent dosing schedule—regular, consistent use is crucial for optimal results
• •Individual variation in response—genetics, metabolism, and other factors affect outcomes
• •Underlying conditions or medications interfering with absorption or effectiveness
• •Improper storage leading to degraded product—always verify proper storage conditions