NEODEXONE COMBINATION PRODUCT EYE OINTMENT

Indications

• Bowel sterilization before surgery
• Hepatic coma
• Topical infections caused by susceptible organisms

Dosage

Children: Refer to the BNF for Children for appropriate dosing information.

Adults: By mouth: 1 g every 1 hour for 4 hours, then 1 g every 4 hours for 2–3 days. For hepatic coma: Up to 4 g daily in divided doses usually for 5–7 days.

Mechanism of action

Neomycin sulfate binds to the 30S ribosomal subunit of bacteria, leading to the misreading of mRNA and the inhibition of protein synthesis. This disrupts the production of essential proteins needed for bacterial growth and function, ultimately resulting in cell death.

Pharmacodynamics

Neomycin demonstrates bactericidal activity against susceptible bacteria. Its efficacy is enhanced in alkaline environments, which is why it is often used in combination with other agents for surgical prophylaxis. The drug is primarily effective against a range of gram-negative organisms, including Escherichia coli and Klebsiella species, but also has some activity against gram-positive organisms.

Pharmacokinetics

Neomycin is poorly absorbed from the gastrointestinal tract, and its systemic absorption is minimal when administered orally. In cases of systemic use, such as intramuscular or intravenous administration, neomycin is distributed widely in the body but is primarily excreted unchanged in the urine. The elimination half-life varies but is generally around 2 to 3 hours in individuals with normal renal function. Monitoring of serum concentrations is essential to prevent toxicity, especially in patients with renal impairment.

Adverse effects

• neurotoxicity
• ototoxicity
• nephrotoxicity
• allergic reactions
• skin rashes
• hearing loss

Interactions

• other nephrotoxic drugs
• loop diuretics
• neuromuscular blocking agents

Precautions

• monitor renal function
• use cautiously in patients with hearing impairment
• avoid concurrent use with other ototoxic medications
• ensure adequate hydration

Pregnancy

Safety in pregnancy has not been established. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Use caution; neomycin can be absorbed systemically and may affect the nursing infant.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• oral tablets
• topical ointments
• injectable solutions

Indications

• Allergic conditions
• Autoimmune disorders (such as lupus and rheumatoid arthritis)
• Certain cancers (e.g., multiple myeloma, leukemias)
• Inflammatory conditions (e.g., asthma, inflammatory bowel disease)
• Cerebral edema
• Adrenal insufficiency
• Post-operative inflammation

Dosage

Adults: Refer to specific

Mechanism of action

Dexamethasone exerts its effects by binding to the glucocorticoid receptor (GR) in the cytoplasm of target cells, which leads to the translocation of the receptor-ligand complex to the nucleus. Once in the nucleus, this complex modulates the expression of specific genes involved in the inflammatory response, resulting in decreased production of pro-inflammatory cytokines and inhibition of immune cell activation. Additionally, dexamethasone influences metabolic processes, including gluconeogenesis, protein metabolism, and lipolysis.

Pharmacodynamics

The pharmacodynamics of dexamethasone involve its potent anti-inflammatory and immunosuppressive effects. It inhibits the accumulation of immune cells at sites of inflammation and decreases the production of inflammatory mediators such as prostaglandins and leukotrienes. Dexamethasone also enhances the responsiveness of the body to catecholamines, which can affect carbohydrate metabolism and promote gluconeogenesis, leading to increased blood glucose levels.

Pharmacokinetics

Dexamethasone is rapidly absorbed after oral administration, with peak plasma concentrations occurring within 1 to 2 hours. It has a high bioavailability due to extensive first-pass metabolism. The drug is primarily metabolized in the liver via CYP3A4 enzymes and has a half-life of approximately 3 to 4 hours, although the biological effects can last significantly longer. Dexamethasone is excreted in the urine, primarily as metabolites, with less than 1% excreted unchanged.

Contra-indications

• Systemic fungal infections
• Hypersensitivity to dexamethasone or any component of the formulation
• Live vaccines in immunosuppressed patients

Adverse effects

• Increased risk of infection
• Hyperglycemia
• Hypertension
• Osteoporosis
• Cushing's syndrome
• Mood changes
• Gastrointestinal disturbances such as peptic ulcers
• Weight gain

Interactions

• Non-steroidal anti-inflammatory drugs (NSAIDs) may increase the risk of gastrointestinal side effects
• Anticoagulants may have altered effects
• Antidiabetic agents may require dosage adjustments due to hyperglycemic effects
• Vaccines may be less effective or cause more severe reactions in immunosuppressed individuals

Precautions

• Use with caution in patients with diabetes, hypertension, or cardiovascular disease
• Monitor for signs of infection
• Tapering may be necessary if used long-term to avoid adrenal insufficiency
• Use with caution in patients with peptic ulcer disease or renal impairment

Pregnancy

Dexamethasone falls under category C. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Dexamethasone is excreted in breast milk. Use with caution and monitor the infant for side effects.

Storage

Store at room temperature, away from light and moisture. Do not freeze.

Formulations

• Oral tablets
• Oral solution
• Injection (intravenous, intramuscular)
• Topical cream

Indications

• Bacterial infections caused by aerobic organisms
• Topical treatment of skin infections

Mechanism of action

Neomycin binds to specific proteins and 16S rRNA within the 30S ribosomal subunit of susceptible bacteria. This binding interferes with the decoding site, causing misreading of mRNA and leading to the incorporation of incorrect amino acids into polypeptides. As a result, nonfunctional or toxic peptides are produced, and polysomes are disrupted into nonfunctional monosomes. Neomycin's bactericidal action is characterized by its ability to irreversibly bind to the 30S ribosomal subunit, thereby inhibiting bacterial protein synthesis.

Pharmacodynamics

Neomycin is primarily active against aerobic bacteria and is not effective against fungi, viruses, or most anaerobic bacteria. It mediates its bactericidal effects by inhibiting protein synthesis, which suppresses bacterial growth and survival. Following oral administration, neomycin exhibits a duration of bactericidal activity lasting between 48 to 72 hours. It is particularly useful in treating infections caused by strains of E. coli and Klebsiella, and it also acts to reduce colonic bacterial populations in patients with hepatic coma.

Pharmacokinetics

Neomycin is poorly absorbed from the gastrointestinal tract when taken orally, which limits its systemic availability and enhances its utility in targeting colonic bacteria. It is generally not used parenterally due to its potential for nephrotoxicity and ototoxicity. The duration of action following oral administration can last from 48 to 72 hours, and it is primarily excreted unchanged in the urine. Caution should be exercised when using neomycin in patients with renal impairment, as the risk of toxicity increases.

Adverse effects

• Nephrotoxicity
• Ototoxicity
• Allergic reactions
• Diarrhea
• Nausea
• Vomiting

Interactions

• neomycin+digoxin: Unknown (decreases absorption)
• neomycin+sorafenib: Unknown (decreases exposure)

Precautions

• Use with caution in patients with renal impairment
• Monitor renal function during therapy
• Evaluate hearing function in long-term use

Pregnancy

Neomycin is classified as category D; it should be used only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Neomycin is excreted in breast milk; caution should be exercised when administered to nursing mothers.

Storage

Store in a cool, dry place away from light. Keep out of reach of children.

Formulations

• Topical ointment
• Cream
• Eye drops
• Oral tablets

Mechanism of action

Framycetin binds to specific 30S-subunit proteins and 16S rRNA, four nucleotides of 16S rRNA and a single amino acid of protein S12. This interferes with decoding site in the vicinity of nucleotide 1400 in 16S rRNA of 30S subunit. This region interacts with the wobble base in the anticodon of tRNA. This leads to interference with the initiation complex, misreading of mRNA so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and the breakup of polysomes into nonfunctional monosomes. Like other aminoglycoside antibiotic drugs, neomycin inhibits bacterial ribosomes by binding to the 30S ribosomal subunit of susceptible bacteria and disrupting the translational machinery of bacterial protein synthesis. Bacterial translation is normally initiated by the mRNA binding to the 30S ribosomal subunit and subsequent binding with 50S subunit for elongation. Aminoglycosides are usually bactericidal in action. Although the exact mechanism of action has not been fully elucidated, the drugs appear to inhibit protein synthesis in susceptible bacteria by irreversibly binding to 30S ribosomal subunits. /Aminoglycosides/ A class of angiogenesis inhibitor has emerged from our mechanistic study of the action of angiogenin, a potent angiogenic factor. Neomycin, an aminoglycoside antibiotic, inhibits nuclear translocation of human angiogenin in human endothelial cells, an essential step for angiogenin-induced angiogenesis. The phospholipase C-inhibiting activity of neomycin appears to be involved, because U-73122, another phospholipase C inhibitor, has a similar effect. In contrast, genistein, oxophenylarsine, and staurosporine, inhibitors of tyrosine kinase, phosphotyrosine phosphatase, and protein kinase C, respectively, do not inhibit nuclear translocation of angiogenin. Neomycin inhibits angiogenin-induced proliferation of human endothelial cells in a dose-dependent manner. At 50 microM, neomycin abolishes angiogenin-induced proliferation but does not affect the basal level of proliferation and cell viability. Other aminoglycoside antibiotics, including gentamicin, streptomycin, kanamycin, amikacin, and paromomycin, have no effect on angiogenin-induced cell proliferation. Most importantly, neomycin completely inhibits angiogenin-induced angiogenesis in the chicken chorioallantoic membrane at a dose as low as 20 ng per egg. These results suggest that neomycin and its analogs are a class of agents that may be developed for anti-angiogenin therapy. ... Aminoglycosides are aminocyclitols that kill bacteria by inhibiting protein synthesis as they bind to the 16S rRNA and by disrupting the integrity of bacterial cell membrane. Aminoglycoside resistance mechanisms include: (a) the deactivation of aminoglycosides by N-acetylation, adenylylation or O-phosphorylation, (b) the reduction of the intracellular concentration of aminoglycosides by changes in outer membrane permeability, decreased inner membrane transport, active efflux, and drug trapping, (c) the alteration of the 30S ribosomal subunit target by mutation, and (d) methylation of the aminoglycoside binding site. ... /Aminoglycosides/

Pharmacodynamics

Framycetin is used for the treatment of bacterial eye infections such as conjunctivitis. Framycetin is an antibiotic. It is not active against fungi, viruses and most kinds of anaerobic bacteria. Framycetin works by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth. Framycetin is useful primarily in infections involving aerobic bacteria bacteria. Neomycin mediates its bactericidal action by inhibiting bacterial protein synthesis, thereby suppressing the growth and survival of susceptible bacteria. Following oral administration, the duration of bactericidal activity of neomycin ranged from 48 to 72 hours. By decreasing colonic bacteria that produce ammonia, neomycin was shown to be effective as an adjunctive therapy in hepatic coma to improve neurologic symptoms. Neomycin is active against both gram positive and gram negative organisms, including the major _E. coli_ species resident in the colon as well as the enteropathogenic forms of _E. coli_. It is also active against _Klebsiella_-_Enterobacter_ group. Resistant strains of _E. coli_, _Klebsiella_ and _Proteus spp_. may emerge from neomycin therapy. Neomycin has no antifungal activity and has some activity against some protozoa.