ALEMTOB D 0.3%W/V, 0.1%W/V SOLUTION

Indications

• Suppression of inflammatory and allergic disorders
• Adjunctive treatment of suspected bacterial meningitis
• Reduction of peri- and neonatal morbidity and mortality in preterm birth
• Management of severe croup
• Congenital adrenal hyperplasia
• COVID-19 requiring supplemental oxygen

Dosage

Adults: For adults, the typical dosing varies by condition

Mechanism of action

Dexamethasone binds to the glucocorticoid receptor, leading to changes in gene expression that result in decreased inflammatory and immune responses. It inhibits phospholipase A2, reducing the formation of pro-inflammatory mediators, and promotes anti-inflammatory genes like interleukin-10. The drug also inhibits neutrophil apoptosis and demargination, contributing to its anti-inflammatory effects. Its glucocorticoid activity results in significant immunosuppression at higher doses.

Pharmacodynamics

Dexamethasone's pharmacodynamics involve the modulation of inflammatory responses through glucocorticoid receptor binding. It inhibits pro-inflammatory signals while promoting anti-inflammatory signals. The duration of action varies based on the administration route, and careful dosing is required to avoid suppression of the hypothalamic-pituitary-adrenal axis and increased infection risk. The drug has a wide therapeutic window, allowing for higher doses than the body's natural production.

Pharmacokinetics

Dexamethasone is well-absorbed after oral administration, with peak plasma concentrations typically occurring within 1-2 hours. It is extensively metabolized in the liver, primarily through hepatic cytochrome P450 enzymes. The elimination half-life ranges from 3 to 4 hours, although it may be longer in certain populations. The drug is excreted mainly in urine as metabolites. The pharmacokinetics can be affected by factors such as liver function and co-administered medications.

Contra-indications

• Systemic fungal infections
• Hypersensitivity to dexamethasone or any component of the formulation
• Active tuberculosis
• Cautious use in patients with peptic ulcer disease

Adverse effects

• Oedema
• Hypotension
• Increased susceptibility to infections
• Mood changes
• Cushing's syndrome
• Hyperglycemia
• Gastrointestinal perforation
• Osteoporosis
• Adrenal suppression

Interactions

• Severe interaction with avapritinib (decreases exposure)
• Moderate interaction with mitotane (decreases exposure)
• Moderate interaction with monoclonal antibodies (decreases exposure)
• Moderate interaction with tocilizumab (decreases exposure)
• Moderate interaction with aprepitant (increases exposure)
• Moderate interaction with netupitant (increases exposure)
• Moderate interaction with rifampicin (decreases exposure)
• Unknown interaction with cobicistat (increases exposure)
• Unknown interaction with caspofungin (decreases concentration)
• Unknown interaction with idelalisib (increases exposure)

Precautions

• Use with caution in patients with a history of tuberculosis
• Monitor for signs of infection due to immunosuppressive effects
• Consider dose adjustments in hepatic impairment
• Taper dosage to avoid withdrawal symptoms after prolonged use
• Monitor blood glucose levels in diabetic patients

Pregnancy

Dexamethasone is classified as a pregnancy category C drug. It should only be used if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Dexamethasone is excreted in breast milk. Caution is advised when administering to breastfeeding women, and the risks versus benefits should be considered.

Storage

Store at room temperature (15-30 degrees Celsius), protect from light, and keep out of reach of children.

Formulations

• Tablet (6 mg)
• Solution for injection (3.3 mg/1 ml)
• Dexamethasone sodium phosphate solution for injection (6.6 mg/2 ml)

Indications

• Bacterial infections (systemic use)
• Septicaemia
• Meningitis and other CNS infections
• Urinary tract infections
• Acute pyelonephritis or prostatitis
• Pneumonia in hospital patients
• Chronic pulmonary Pseudomonas aeruginosa infection in patients with cystic fibrosis

Mechanism of action

Tobramycin binds to the bacterial 30S ribosomal subunit, disrupting protein synthesis. This binding causes misreading of mRNA, leading to the production of non-functional proteins. Additionally, tobramycin increases the permeability of the bacterial cell membrane, facilitating further entry of the drug. This dual action results in both immediate and delayed bactericidal effects.

Pharmacodynamics

Tobramycin has a broad spectrum of activity against a variety of Gram-negative bacteria including Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, as well as some Gram-positive organisms such as Staphylococcus spp. It is particularly effective in treating infections associated with cystic fibrosis and serious hospital-acquired infections. Due to its mechanism of action, tobramycin is also associated with potential toxic effects, especially in renal and auditory systems.

Pharmacokinetics

Tobramycin is poorly absorbed from the gastrointestinal tract, necessitating parenteral administration for systemic effects. It is distributed widely in body fluids, including synovial and peritoneal fluids, and it crosses the placenta. The drug is primarily excreted unchanged in the urine, and its half-life is approximately 2 hours in normal renal function, extending in cases of renal impairment. Monitoring of serum tobramycin levels is essential to avoid toxicity, particularly nephrotoxicity and ototoxicity.

Contra-indications

• History of hypersensitivity to tobramycin or other aminoglycosides
• Severe renal impairment
• Pre-existing auditory or vestibular disorders

Adverse effects

• Ototoxicity
• Nephrotoxicity
• Electrolyte imbalance
• Diarrhoea
• Nausea
• Vomiting
• Confusion
• Paraesthesia
• Malaise
• Respiratory disorders
• Abdominal pain
• Drowsiness
• Ear disorders
• Asthenia
• Sputum discolouration
• Hypertension

Interactions

• Increased risk of nephrotoxicity with other nephrotoxic agents
• Potentially decreased exposure with miconazole
• Enhanced neuromuscular blockade when used with neuromuscular blockers

Precautions

• Monitor renal function before and during treatment
• Auditory and vestibular function should be monitored during treatment
• Caution in patients with pre-existing neuromuscular disorders
• Use with caution in hepatic impairment

Pregnancy

There is a risk of auditory or vestibular nerve damage in the infant when aminoglycosides are used in the second and third trimesters of pregnancy.

Breast-feeding

Tobramycin is excreted in breast milk; caution is advised when administering to breastfeeding mothers.

Storage

Store in a cool, dry place away from direct sunlight. Protect from moisture.

Formulations

• Injectable solution (e.g., 300 mg/5 mL)
• Nebulised solution (e.g., 170 mg every 12 hours for 28 days)
• Ophthalmic ointment (e.g., applied 3 times a day for 5 days)
• Oral solution (e.g., 125 mg/5 mL)

Mechanism of action

The short term effects of corticosteroids are decreased vasodilation and permeability of capillaries, as well as decreased leukocyte migration to sites of inflammation. Corticosteroids binding to the glucocorticoid receptor mediates changes in gene expression that lead to multiple downstream effects over hours to days. Glucocorticoids inhibit neutrophil apoptosis and demargination; they inhibit phospholipase A2, which decreases the formation of arachidonic acid derivatives; they inhibit NF-Kappa B and other inflammatory transcription factors; they promote anti-inflammatory genes like interleukin-10. Lower doses of corticosteroids provide an anti-inflammatory effect, while higher doses are immunosuppressive. High doses of glucocorticoids for an extended period bind to the mineralocorticoid receptor, raising sodium levels and decreasing potassium levels. Corticosteroids diffuse across cell membranes and complex with specific cytoplasmic receptors. These complexes then enter the cell nucleus, bind to DNA, and stimulate transcription of mRNA and subsequent protein synthesis of enzymes ultimately responsible for anti-inflammatory effects of topical application of corticosteroids to the eye. In high concentrations which may be achieved after topical application, corticosteroids may exert direct membrane effects. Corticosteroids decrease cellular and fibrinous exudation and tissue infiltration, inhibit fibroblastic and collagen-forming activity, retard epithelial regeneration, diminish postinflammatory neovascularization and reduce toward normal levels the excessive permeability of inflamed capillaries. /Corticosteroids (Otic)/ Glucocorticoids are capable of suppressing the inflammatory process through numerous pathways. They interact with specific intracellular receptor proteins in target tissues to alter the expression of corticosteroid-responsive genes. Glucocorticoid-specific receptors in the cell cytoplasm bind with steroid ligands to form hormone-receptor complexes that eventually translocate to the cell nucleus. There these complexes bind to specific DNA sequences and alter their expression. The complexes may induce the transcription of mRNA leading to synthesis of new proteins. Such proteins include lipocortin, a protein known to inhibit PLA2a and thereby block the synthesis of prostaglandins, leukotrienes, and PAF. Glucocorticoids also inhibit the production of other mediators including AA metabolites such as COX, cytokines, the interleukins, adhesion molecules, and enzymes such as collagenase. /Glucocorticoids/ Corticosteroids diffuse across cell membranes and complex with specific cytoplasmic receptors. These complexes then enter the cell nucleus, bind to DNA (chromatin), and stimulate transcription of messenger RNA (mRNA) and subsequent protein synthesis of various inhibitory enzymes responsible for the anti-inflammatory effects of topical corticosteroids. These anti-inflammatory effects include inhibition of early processes such as edema, fibrin deposition, capillary dilatation, movement of phagocttes into the area, and phagocytic activities. Later processes, such as capillary production, collagen deposition, and keloid formation also are inhibited by corticosteroids. The overall actions of topical corticosteroids are catabolic. /Corticosteroids (topical)/

Pharmacodynamics

Corticosteroids bind to the glucocorticoid receptor, inhibiting pro-inflammatory signals, and promoting anti-inflammatory signals. Dexamethasone's duration of action varies depending on the route. Corticosteroids have a wide therapeutic window as patients may require doses that are multiples of what the body naturally produces. Patients taking corticosteroids should be counselled regarding the risk of hypothalamic-pituitary-adrenal axis suppression and increased susceptibility to infections.

Mechanism of action

Tobramycin is a 4,6-disubstituted 2-deoxystreptamine (DOS) ring-containing aminoglycoside antibiotic with activity against various Gram-negative and some Gram-positive bacteria. The mechanism of action of tobramycin has not been unambiguously elucidated, and some insights into its mechanism rely on results using similar aminoglycosides. In general, like other aminoglycosides, tobramycin is bactericidal and exhibits both immediate and delayed killing, which are attributed to different mechanisms, as outlined below. Aminoglycosides are polycationic at physiological pH, such that they readily bind to bacterial membranes ("ionic binding"); this includes binding to lipopolysaccharide and phospholipids within the outer membrane of Gram-negative bacteria and to teichoic acid and phospholipids within the cell membrane of Gram-positive bacteria. This binding displaces divalent cations and increases membrane permeability, which allows aminoglycoside entry. Additional aminoglycoside entry ("energy-dependent phase I") into the cytoplasm requires the proton-motive force, allowing access of the aminoglycoside to its primary intracellular target of the bacterial 30S ribosome. Mistranslated proteins produced as a result of aminoglycoside binding to the ribosome (see below) integrate into and disrupt the cell membrane, which allows more of the aminoglycoside into the cell ("energy-dependent phase II"). Hence, tobramycin and other aminoglycosides have both immediate bactericidal effects through membrane disruption and delayed bactericidal effects through impaired protein synthesis; observed experimental data and mathematical modelling support this two-mechanism model. Inhibition of protein synthesis was the first recognized effect of aminoglycoside antibiotics. Structural and cell biological studies suggest that aminoglycosides bind to the 16S rRNA in helix 44 (h44), near the A site of the 30S ribosomal subunit, altering interactions between h44 and h45. This binding also displaces two important residues, A1492 and A1493, from h44, mimicking normal conformational changes that occur with successful codon-anticodon pairing in the A site. Overall, aminoglycoside binding has several negative effects, including inhibiting translation initiation and elongation and ribosome recycling. Recent evidence suggests that the latter effect is due to a cryptic second binding site situated in h69 of the 23S rRNA of the 50S ribosomal subunit. Also, by stabilizing a conformation that mimics correct codon-anticodon pairing, aminoglycosides promote error-prone translation; mistranslated proteins can incorporate into the cell membrane, inducing the damage discussed above. Although direct mutation of the 16S rRNA is a rare resistance mechanism, due to the gene being present in numerous copies, posttranscriptional 16S rRNA modification by 16S rRNA methyltransferases (16S-RMTases) at the N7 position of G1405 or the N1 position of A1408 are common resistance mechanisms in aminoglycoside-resistant bacteria. These mutants also further support the proposed mechanism of action of aminoglycosides. Direct modification of the aminoglycoside itself through acetylation, adenylation, and phosphorylation by aminoglycoside-modifying enzymes (AMEs) are also commonly encountered resistance mutations. Finally, due to the requirement for active transport of aminoglycosides across bacterial membranes, they are not active against obligately anaerobic bacteria. Aminoglycosides are usually bacterial 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/ ... 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-acetyl

Pharmacodynamics

Tobramycin is an aminoglycoside antibiotic derived from the actinomycete _Streptomyces tenebrarius_. It has a broad spectrum of activity against Gram-negative bacteria, including _Enterobacteriaceae_, _Escherichia coli_, _Klebsiella pneumoniae_, _Morganella morganii_, _Moraxella lacunata_, _Proteus_ spp., _Haemophilus_ spp., _Acinetobacter_ spp., _Neisseria_ spp., and, importantly, _Pseudomonas aeruginosa_. Aminoglycosides also generally retain activity against the biothreat agents _Yersinia pestis_ and _Francisella tularensis_. In addition, aminoglycosides are active against some Gram-positive bacteria such as _Staphylococcus_ spp., including methicillin-resistant (MRSA) and vancomycin-resistant strains, _Streptococcus_ spp., and _Mycobacterium_ spp. Like other aminoglycosides, tobramycin is taken up and retained by proximal tubule and cochlear cells in the kidney and ear, respectively, and hence carries a risk of nephrotoxicity and ototoxicity. There is also a risk of neuromuscular block, which may be more pronounced in patients with preexisting neuromuscular disorders such as myasthenia gravis or Parkinson's disease. Aminoglycosides can cross the placenta, resulting in total, irreversible, bilateral congenital deafness in babies born to mothers who were administered an aminoglycoside during pregnancy. Due to the low systemic absorption of inhaled and topical tobramycin formulations, these effects are more pronounced with injected tobramycin than with other formulations. However, all formulations carry a risk of hypersensitivity reactions, including potentially fatal cutaneous reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis.