Comparative Pharmacology
Head-to-head clinical analysis: GENOSYL versus NEOMYCIN AND POLYMYXIN B SULFATES AND GRAMICIDIN.
Peer-Reviewed Evidence
Head-to-head clinical analysis: GENOSYL versus NEOMYCIN AND POLYMYXIN B SULFATES AND GRAMICIDIN.
GENOSYL vs NEOMYCIN AND POLYMYXIN B SULFATES AND GRAMICIDIN
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Genosyl (sodium phenylbutyrate) is a prodrug that is metabolized to phenylacetate, which conjugates with glutamine via acetylation to form phenylacetylglutamine. This alternative pathway facilitates waste nitrogen excretion in patients with urea cycle disorders.
Neomycin and gramicidin are aminoglycoside and polypeptide antibiotics, respectively, that inhibit bacterial protein synthesis by binding to the 30S and 50S ribosomal subunits, while polymyxin B is a cationic detergent that disrupts bacterial cell membrane integrity by binding to lipopolysaccharides.
5 mg orally once daily for 14 days, then 2.5 mg orally once daily thereafter.
1-2 drops or a small amount applied to affected eye(s) every 4 hours, or more frequently if severe, for up to 7-10 days. Ophthalmic ointment: apply a 1/2-inch ribbon into conjunctival sac every 3-4 hours.
None Documented
None Documented
Terminal half-life 3.5 hours; clinically relevant for dosing every 6-8 hours in renal impairment.
Neomycin: plasma half-life ~2-3 hours in patients with normal renal function, but can extend to 12-24 hours or more in renal impairment. Polymyxin B: half-life ~6 hours in normal renal function, prolonged significantly in renal failure (up to 2-3 days). Gramicidin: not systemically absorbed; half-life not applicable.
Renal: 85% unchanged; biliary/fecal: 15% as metabolites.
Neomycin and polymyxin B sulfates and gramicidin are poorly absorbed from intact skin or ophthalmic sites. After topical application, absorbed neomycin is excreted primarily unchanged in urine (30-50% of absorbed dose) via glomerular filtration; polymyxin B is excreted slowly via renal tubular secretion and glomerular filtration (60-70% of absorbed dose in urine); fecal elimination accounts for minor amounts. Gramicidin is not significantly absorbed.
Category C
Category A/B
Aminoglycoside Antibiotic
Aminoglycoside Antibiotic