MILFLOX DM

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
• Complicated skin and soft-tissue infections
• Pelvic inflammatory disease
• Respiratory tract infections
• Intra-abdominal infections

Dosage

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

Adults: 400 mg once daily for 7-21 days, depending on the specific infection being treated.

Mechanism of action

Moxifloxacin's bactericidal effect is primarily due to its inhibition of the enzymes topoisomerase II (DNA gyrase) and topoisomerase IV. By interfering with these enzymes, moxifloxacin prevents the replication, transcription, and repair of bacterial DNA. This mechanism is crucial for bacterial cell division and survival.

Pharmacodynamics

As a quinolone antibiotic, moxifloxacin is effective against a range of bacteria including aerobic Gram-positive organisms such as _Staphylococcus aureus_ and _Streptococcus pneumoniae_, as well as Gram-negative organisms like _Haemophilus influenzae_. It is known for its high affinity for bacterial DNA gyrase, which is approximately 100 times greater than its affinity for mammalian enzymes, making it selectively toxic to bacteria.

Pharmacokinetics

Moxifloxacin exhibits good oral bioavailability and is widely distributed in body tissues, reaching peak plasma concentrations approximately 1 to 2 hours after administration. The drug is primarily metabolized in the liver and excreted via the urine. The half-life of moxifloxacin is approximately 12 hours, allowing for once-daily dosing.

Contra-indications

• Acute myocardial infarction (risk factor for QT interval prolongation)
• Bradycardia (risk factor for QT interval prolongation)
• Congenital long QT syndrome (risk factor for QT interval prolongation)
• Electrolyte disturbances (risk factor for QT interval prolongation)
• Heart failure with reduced left ventricular ejection fraction (risk factor for QT interval prolongation)
• History of symptomatic arrhythmias (risk factor for QT interval prolongation)

Adverse effects

• Increased risk of infection
• Akathisia
• Angina pectoris
• Colitis associated with antibiotics
• Asthma
• Dehydration
• Gastritis
• Hyperlipidaemia
• Malaise
• Oedema
• Pelvic pain
• Thrombocytosis
• Vasodilation

Precautions

• May impair performance of skilled tasks (e.g. driving)
• Use with caution in patients with a history of seizures or CNS disorders

Pregnancy

Manufacturer advises use only if potential benefit outweighs risk.

Breast-feeding

Manufacturer advises avoid-present in milk in animal studies.

Storage

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

Formulations

• Tablets 400 mg
• Injection solution 400 mg/250 ml
• Nebuliser solution 100 mg/1 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

The bactericidal action of moxifloxacin results from inhibition of the enzymes topoisomerase II (DNA gyrase) and topoisomerase IV. DNA gyrase is an essential enzyme that is involved in the replication, transcription and repair of bacterial DNA. Topoisomerase IV is an enzyme known to play a key role in the partitioning of the chromosomal DNA during bacterial cell division. The fluoroquinolone antibiotic moxifloxacin has been associated with the acquired long QT syndrome and is used as a positive control in the evaluation of the QT-interval prolonging potential of new drugs. In common with other QT-prolonging agents, moxifloxacin is known to inhibit the hERG potassium K+ channel, but at present there is little mechanistic information available on this action. This study was conducted in order to characterise the inhibition of hERG current (I(hERG)) by moxifloxacin, and to determine the role in drug binding of the S6 aromatic amino-acid residues Tyr652 and Phe656. hERG currents were studied using whole-cell patch clamp (at room temperature and at 35-37 degrees C) in an HEK293 cell line stably expressing hERG channels. Moxifloxacin reversibly inhibited currents in a dose-dependent manner. We investigated the effects of different voltage commands to elicit hERG currents on moxifloxacin potency. Using a 'step-ramp' protocol, the IC50 was 65 uM at room temperature and 29 microM at 35 degrees C. When a ventricular action potential waveform was used to elicit currents, the IC50 was 114 microM. Block of hERG by moxifloxacin was found to be voltage-dependent, occurred rapidly and was independent of stimulation frequency. Mutagenesis of the S6 helix residue Phe656 to Ala failed to eliminate or reduce the moxifloxacin-mediated block whereas mutation of Tyr652 to Ala reduced moxifloxacin block by approximately 66%. Our data demonstrate that moxifloxacin blocks the hERG channel with a preference for the activated channel state. The Tyr652 but not Phe656 S6 residue is involved in moxifloxacin block of hERG, concordant with an interaction in the channel inner cavity. The bactericidal action of moxifloxacin results from inhibition of the topoisomerase II (DNA gyrase) and topoisomerase IV required for bacterial DNA replication, transcription, repair, and recombination. It appears that the C8-methoxy moiety contributes to enhanced activity and lower selection of resistant mutants of Gram-positive bacteria compared to the C8-H moiety. The presence of the bulky bicycloamine substituent at the C-7 position prevents active efflux, associated with the NorA or pmrA genes seen in certain Gram-positive bacteria. Torsade de pointes (TdP) is increasingly recognized as a complication of drug therapy. The most common cause of drug-induced QT prolongation is inhibition of the rapidly activating component of the delayed potassium current (I(Kr)). Moxifloxacin, a widely used fluoroquinolone, is a weak I(Kr) inhibitor and has been associated with QT prolongation. Fluoroquinolones prolong the QT interval by blocking voltage-gated potassium channels, especially the rapid component of the delayed rectifier potassium current I(Kr), expressed by HERG (the human ether-a-go-go-related gene). According to the available case reports and clinical studies, moxifloxacin carries the greatest risk of QT prolongation from all available quinolones in clinical practice and it should be used with caution in patients with predisposing factors for Torsades de pointes (TdP).

Pharmacodynamics

Moxifloxacin is a quinolone/fluoroquinolone antibiotic. Moxifloxacin can be used to treat infections caused by the following bacteria: Aerobic Gram-positive microorganisms: _Corynebacterium_ species, _Micrococcus luteus_, _Staphylococcus aureus_, _Staphylococcus epidermidis_, _Staphylococcus haemolyticus_, _Staphylococcus hominis_, _Staphylococcus warneri_, _Streptococcus pneumoniae_, and _Streptococcus viridans_ group. Aerobic Gram-negative microorganisms: _Acinetobacter lwoffii_, _Haemophilus influenzae_, and _Haemophilus parainfluenzae_. Other microorganisms: _Chlamydia trachomatis_. Moxifloxacin is bactericidal and its mode of action depends on blocking of bacterial DNA replication by binding itself to an enzyme called DNA gyrase, which allows the untwisting required to replicate one DNA double helix into two. Notably the drug has 100 times higher affinity for bacterial DNA gyrase than for mammalian. Moxifloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and Gram-negative bacteria.