Neomycin

Neomycin

Clinical data
Routes of administration	Topical, Oral
ATC code	A01AB08 (WHO) A07AA01 (WHO), B05CA09 (WHO), D06AX04 (WHO), J01GB05 (WHO), R02AB01 (WHO), S01AA03 (WHO), S02AA07 (WHO), S03AA01 (WHO)
Legal status
Legal status	OTC
Pharmacokinetic data
Elimination half-life	2 to 3 hours
Identifiers
IUPAC name (1R,2R,3S,4R,6S)-4,6-diamino-2- {[3-O-(2,6-diamino-2,6-dideoxy-β-L-idopyranosyl)- β-D-ribofuranosyl]oxy}-3-hydroxycyclohexyl 2,6-diamino-2,6-dideoxy-α-D-glucopyranoside
CAS Number	1404-04-2
PubChem CID	8378
IUPHAR/BPS	709
DrugBank	APRD00013
ChemSpider	8075
ECHA InfoCard	100.014.333
Chemical and physical data
Formula	C23H46N6O13
Molar mass	614.644 g/mol g·mol−1

Neomycin is an aminoglycoside antibiotic that is found in many topical medications such as creams, ointments, and eyedrops.

Uses

Neomycin is overwhelmingly used as a topical preparation, such as Neosporin. It can also be given orally, where it is usually combined with other antibiotics. Neomycin is not absorbed from the gastrointestinal tract, and has been used as a preventive measure for hepatic encephalopathy and hypercholesterolemia. By killing bacteria in the intestinal tract, it keeps ammonia levels low and prevents hepatic encephalopathy, especially prior to GI surgery. It has also been used to treat small intestinal bacterial overgrowth. It is not given intravenously, as neomycin is extremely nephrotoxic (causes kidney damage), especially compared to other aminoglycosides. The exception is when neomycin is included, in very small quantities, as a preservative in some vaccines - typically 0.025 mg per dose.

Molecular biology

Neomycin resistance is conferred by either one of two aminoglycoside phosphotransferase genes. A neo gene is commonly included in DNA plasmids used by molecular biologists to establish stable mammalian cell lines expressing cloned proteins in culture; many commercially available protein expression plasmids contain neo as a selectable marker. Non-transfected cells will eventually die off when the culture is treated with neomycin or similar antibiotic. Neomycin or kanamycin can be used for prokaryotes, but geneticin (G418) is generally needed for eukaryotes.

Spectrum

Similar to other aminoglycosides, neomycin has excellent activity against Gram negative bacteria, and has partial activity against Gram positive bacteria. It is relatively toxic to humans, and many people have allergic reactions to it. See: Hypersensitivity. Physicians sometimes recommend using antibiotic ointments without neomycin, such as Polysporin.

History

Neomycin was discovered in 1949 by the microbiologist Selman Waksman and his student Hubert Lechevalier at Rutgers University. It is produced naturally by the bacterium Streptomyces fradiae.

Neomycin as a DNA binder

Neomycin belongs to the family of aminoglycosides. This family includes many other medicinally important drugs: streptomycin, Paromomycin and kanamycin to name just a few. Aminoglycosides are proverbially known for their ability to bind to duplex RNA with high affinity. A study done by Daniel Pilch, Associate Professor Dept. of Pharmacology at Rutgers University, and his coworkers, determined the association constant for neomycin with A-site RNA was found to be in the ~10⁹ range. However more than 50 years after its discovery, its DNA binding properties were still unknown. In 2000, Dev P. Arya, currently Director of the Laboratory of Medicinal Chemistry at Clemson University, and his coworkers discovered that neomycin induces enormous thermal stabilization of triplex DNA while having little or almost no effect on the DNA duplex stabilization. They also showed that, neomycin binds anything that adopts A-form type structure, triplex DNA being one of them. They later went on to show that neomycin even induces DNA:RNA hybrid triplex formation. Their continuous search for selective ligands for a particular type of nucleic acid gave rise to many new conjugates. Neomycin-BQQ when they tried to combined the best in triplex recognition, Neomycin-Hoechst 33258 conjugate for targeting B-DNA (neomycin alone doesn't bind to a typical duplex B-DNA) and Neomycin Methidium conjugate for targeting DNA:RNA hybrids.