dexamethasone/ tobramycin

Action and Spectrum

Actions and Spectrum: 

• tobramycin is an antibiotic that belongs to the class of aminoglycosides. It works by binding to the bacterial ribosomes and inhibiting protein synthesis. tobramycin is active against many gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli, Klebsiella, and Proteus species. It is commonly used to treat respiratory, skin, urinary, and bloodstream infections. 
• dexamethasone is a corticosteroid that suppresses the immune response and reduces inflammation. It binds to specific intracellular receptors, and this complex then regulates gene expression by altering the transcription of specific genes. dexamethasone is used in various conditions such as allergic reactions, asthma, inflammatory bowel disease, rheumatoid arthritis, and other autoimmune conditions. It is also combined with antibiotics to reduce eye and ear inflammation. 
• When combined, tobramycin and dexamethasone are often prescribed as ear drops to treat ear canal infections and inflammation. tobramycin kills bacteria that cause infections, while dexamethasone reduces inflammation and swelling in the ear. This combination therapy is effective against many bacterial strains, including those resistant to other antibiotics. 

Drug Interaction

Adverse Reaction

Frequency not defined 

Conjunctival erythema 

development of glaucoma 

Cataract formation 

Delayed wound healing 

Keratitis 

Ocular lid itching and swelling 

Elevation of intraocular pressure (IOP) with possible 

Infrequent optic nerve damage 

Posterior subcapsular cataract formation 

Secondary infections 

Post-marketing reports 

Erythema multiforme 

Anaphylactic reaction 

Black Box Warning

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

• Hypersensitivity: Individuals allergic to tobramycin, dexamethasone, or any of their components should not use these medications. 
• Viral infections: tobramycin and dexamethasone should not be used to treat viral infections like herpes simplex or varicella because they can worsen the infection. 
• Fungal infections: These medications should not be used to treat fungal infections because they can promote the growth of fungi. 
• Myasthenia gravis: tobramycin and dexamethasone can exacerbate muscle weakness in patients with myasthenia gravis. 
• Corneal ulcers: tobramycin and dexamethasone should not be used to treat corneal ulcers caused by fungi or viruses. 
• Pregnancy and lactation: Using these medications during pregnancy and lactation should be avoided as they can harm the developing fetus or infant. 

Caution: 

• Renal impairment: tobramycin is primarily excreted by the kidneys, and its dose may need to be adjusted in patients with impaired renal function to avoid toxic levels in the bloodstream. 
• Neurotoxicity: Aminoglycosides like tobramycin can cause neurotoxicity, mainly when used in high doses or for prolonged periods. Symptoms of neurotoxicity include hearing loss, tinnitus, vertigo, and difficulty with coordination. 
• Gastrointestinal effects: dexamethasone can cause gastrointestinal side effects, such as nausea, vomiting, and abdominal pain. 
• Glaucoma: dexamethasone can increase intraocular pressure, which may worsen glaucoma. 
• Diabetes: dexamethasone can increase blood glucose levels, which may be problematic for individuals with diabetes. 
• Immunocompromised individuals: Immunocompromised individuals, such as those with HIV, may be more susceptible to infections when using tobramycin and dexamethasone. 
• Use in pediatric patients: Caution should be exercised when using tobramycin and dexamethasone, especially for those under six months, as they may be more susceptible to adverse effects. 

Pregnancy / Lactation

Pregnancy consideration: Insufficient data available 

Lactation:  

• Excretion of the drug in human breast milk is in small amounts 
• The use of tobramycin and dexamethasone during lactation should be approached with caution 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

• tobramycin is an aminoglycoside antibiotic that works by inhibiting bacterial protein synthesis. It binds to the 30S ribosomal subunit of bacteria and interferes with the initiation and elongation of protein synthesis, leading to bacterial cell death. tobramycin has a broad spectrum of activity and is effective against gram-negative bacteria, including Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Proteus species. 
• dexamethasone is a synthetic glucocorticoid steroid that has anti-inflammatory and immunosuppressive effects. It binds to the cytoplasmic glucocorticoid receptor and forms a complex that regulates gene expression. This leads to suppressing pro-inflammatory cytokines and chemokines, resulting in decreased inflammation and immune response. dexamethasone also has anti-allergic effects and treats various conditions, including asthma, rheumatoid arthritis, and inflammatory bowel disease. 

Pharmacodynamics: 

The pharmacodynamics of tobramycin and dexamethasone are related to their pharmacological actions. 

• tobramycin exerts its antibacterial effect by binding to the bacterial ribosomes and disrupting protein synthesis, leading to cell death. The pharmacodynamic properties of tobramycin include concentration-dependent killing, a post-antibiotic effect, and a dose-dependent increase in bacterial eradication. Concentration-dependent killing means that the bactericidal activity of tobramycin increases with increasing drug concentration up to a certain maximum level. The post-antibiotic effect refers to the ongoing bactericidal activity of tobramycin even after removing the drug from the bacterial environment. This effect may be significant in treating bacterial infections, allowing for longer intervals between doses. 

• dexamethasone exerts its anti-inflammatory and immunosuppressive effects by modulating gene expression in various cells, including immune cells. The pharmacodynamic properties of dexamethasone include dose-dependent suppression of inflammatory mediators, inhibition of immune cell activation and migration, and modulation of cytokine production. dexamethasone has been shown to reduce the production of pro-inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha), and increase the production of anti-inflammatory cytokines, such as interleukin-10 (IL-10). 
• Combined, tobramycin and dexamethasone work synergistically to treat ear infections and inflammation. Tobramycin kills bacteria, while dexamethasone reduces inflammation and swelling in the ear. The combination is effective against many bacterial strains, including those resistant to other antibiotics. 

Pharmacokinetics: 

Absorption 

tobramycin is typically administered topically as an ointment, solution, or suspension for ear, eye, or skin infections. When administered orally, tobramycin is not well absorbed and is usually given intravenously. When given intravenously, tobramycin has a rapid onset of action. 

dexamethasone is available in various formulations, including oral tablets, intravenous injections, topical creams, and ophthalmic solutions. The oral and topical formulations are well absorbed, while the intravenous formulation has a rapid onset of action.  

Distribution 

tobramycin is distributed widely throughout the body, including the lungs, kidneys, and tissues. The drug can cross the placenta and enter breast milk. 

dexamethasone is distributed widely throughout the body, including the brain and other tissues. The drug can cross the placenta and enter breast milk.  

Metabolism 

tobramycin is not metabolized significantly by the liver and is excreted primarily unchanged in the urine. 

dexamethasone is metabolized by the liver and excreted in the urine as metabolites.  

Elimination and Excretion 

tobramycin is excreted primarily unchanged in the urine, with a half-life of about 2 hours in patients with normal renal function. 

dexamethasone is excreted in the urine and feces, with a half-life of 36 to 54 hours. 

Adminstartion

Administration: 

tobramycin and dexamethasone are available in various formulations and can be administered via different routes depending on the treated condition. Here are some standard administration methods for each drug: 

• Ophthalmic solution: To treat bacterial eye infections, tobramycin is typically administered as an ophthalmic solution. The usual dosage is 1 or 2 drops into the affected eye(s) every 4 to 6 hours, depending on the severity of the infection. 
• Ophthalmic solution: dexamethasone is also available as an ophthalmic solution for the treatment of eye conditions, such as inflammation and allergies. The usual dosage is 1 or 2 drops into the affected eye(s) 2 to 4 times per day. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: dexamethasone/ tobramycin 

Why do we use dexamethasone/ tobramycin? 

tobramycin and dexamethasone are often used as topical medications for treating eye infections and inflammation. Here are some common uses of these drugs: 

• Eye infections: tobramycin and dexamethasone are used in an ophthalmic solution to treat eye infections caused by bacteria. Tobramycin is an antibiotic that helps to kill the bacteria causing the infection, while dexamethasone is a steroid that helps to reduce inflammation and swelling in the eye. 
• Eye inflammation: tobramycin and dexamethasone are also used in an ophthalmic solution to treat inflammation and swelling in the eye caused by conditions such as uveitis, conjunctivitis, and allergic reactions. 
• Skin infections: tobramycin can be applied topically as a solution or ointment to treat skin infections caused by bacteria. 
• Inflammatory and allergic disorders: dexamethasone is a steroid administered orally, topically, or intravenously to treat various inflammatory and allergic conditions, such as asthma, rheumatoid arthritis, and skin disorders eczema and psoriasis.