1. Gramicidin D Drugbank ID : DB00027
Protein chemical formula : C99H140N20O17
Protein average weight :

2. Description : Indication : Pharmacodynamics :
Gramcidin D is a heterogeneous mixture of three antibiotic compounds, gramicidins A, B and C, making up 80%, 6%, and 14% respectively all of which are obtained from the soil bacterial species Bacillus brevis and called collectively gramicidin D. Gramcidins are 15 residue peptides with alternating D and L amino acids. The peptides assemble inside of the hydrophobic interior of the cellular lipid bilayer to form a β-helix. The helix itself is not long enough to span the membrane but it dimerizes to form the elongated channel needed to span the whole membrane. Gramicidin D is used primarily as a topical antibiotic and is one of the three constituents of consumer antibiotic polysporin ophthalmic solution.
Indication :
For treatment of skin lesions, surface wounds and eye infections.
Pharmacodynamics :
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

3. Mechanism of action : Categories :
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.
Categories :
Anti-Bacterial Agents and Anti-Infective Agents and Antibiotics and Antibiotics, Topical

4. Brands : Neosporin
Company : Pfizer
Description : NEOSPORIN Ophthalmic Ointment (neomycin, polymyxin and bacitracin zinc ophthalmic ointment) (neomycin and polymyxin B sulfates and bacitracin zinc ophthalmic ointment) is a sterile antimicrobial ointment for ophthalmic use. Neomycin sulfate is the sulfate salt of neomycin B and C, which are produced by the growth of Streptomyces fradiae Waksman (Fam. Streptomycetaceae). It has a potency equivalent of not less than 600 µg of neomycin standard per mg, calculated on an anhydrous basis. Polymyxin B sulfate is the sulfate salt of polymyxin B1 and B2, which are produced by the growth of Bacillus polymyxa (Prazmowski) Migula (Fam. Bacillaceae). It has a potency of not less than 6,000 polymyxin B units per mg, calculated on an anhydrous basis.Bacitracin zinc is the zinc salt of bacitracin, a mixture of related cyclic polypeptides (mainly bacitracin A) produced by the growth of an organism of the licheniformis group of Bacillus subtilis var Tracy. It has a potency of not less than 40 bacitracin units per mg.
Used for/Prescribed for : Treating and preventing infection due to minor cuts, scrapes, and burns. Neosporin ointment is an antibiotic combination. It works by killing sensitive bacteria on the skin or in wounds.
Formulation : Each gram contains: neomycin sulfate equivalent to 3.5 mg neomycin base, polymyxin B sulfate equivalent to 10,000 polymyxin B units, bacitracin zinc equivalent to 400 bacitracin units, and white petrolatum, q.s.
Form : ointment

5. Route of administration : for external use only Dosage : Apply the ointment every 3 or 4 hours for 7 to 10 days, depending on the severity of the infection. Contraindication : contraindicated in individuals who have shown hypersensitivity to any of its components Side effects : Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); skin irritation, pain, burning, cracking, redness, or peeling not present before using Neosporin ointment; worsening or recurrence of wound symptoms. Drug interaction : A total of 19 drugs (48 brand and generic names) are known to interact moderately with Neosporin (bacitracin / neomycin / polymyxin b topical)

6. General references :
# Ketchem RR, Lee KC, Huo S, Cross TA: Macromolecular structural elucidation with solid-state NMR-derived orientational constraints. J Biomol NMR Jul;8(1):1-14. "Pubmed":
# Townsley LE, Tucker WA, Sham S, Hinton JF: Structures of gramicidins A, B, and C incorporated into sodium dodecyl sulfate micelles. Biochemistry Oct 2;40(39): "Pubmed":
# Burkhart BM, Gassman RM, Langs DA, Pangborn WA, Duax WL, Pletnev V: Gramicidin D conformation, dynamics and membrane ion transport. Biopolymers. 1999;51(2): "Pubmed":

7. References : http://www. drugs. com/cdi/neosporin-ointment