MAXIDEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MAXIDEX (MAXIDEX).
MAXIDEX (dexamethasone) is a potent glucocorticoid that binds to the glucocorticoid receptor (GR), leading to modulation of gene expression and inhibition of inflammatory mediators such as prostaglandins and leukotrienes. It suppresses immune response through inhibition of cytokine production (e.g., IL-1, IL-2, TNF-alpha) and reduces vasodilation and vascular permeability.
| Metabolism | Primarily hepatic via cytochrome P450 enzymes (CYP3A4); undergoes extensive metabolism to inactive metabolites, which are excreted in the urine. |
| Excretion | Primarily hepatic metabolism via CYP3A4; renal excretion of metabolites accounts for <15% unchanged drug; biliary/fecal elimination of metabolites predominates. |
| Half-life | Terminal elimination half-life is approximately 2-3 hours for dexamethasone; in ocular tissues, half-life may be prolonged due to local retention, but systemic half-life is short with minimal accumulation. |
| Protein binding | Approximately 77% bound to albumin and corticosteroid-binding globulin (transcortin). |
| Volume of Distribution | Volume of distribution is approximately 0.5-1.0 L/kg, indicating distribution throughout total body water and significant tissue penetration. |
| Bioavailability | Topical ophthalmic: Minimal systemic absorption (<1%) via conjunctival and nasal mucosa; oral: approximately 80-90% absorbed with high first-pass metabolism, resulting in effective oral bioavailability of about 60-80%. |
| Onset of Action | Topical ophthalmic: Onset of anti-inflammatory effect occurs within 2-4 hours after instillation; systemic (oral): 1-2 hours. |
| Duration of Action | Topical ophthalmic: Duration of anti-inflammatory effect is 6-8 hours, requiring frequent dosing (e.g., every 4-6 hours); systemic: biologic half-life of metabolic effects (e.g., cortisol suppression) lasts 24-36 hours. |
One to two drops of the 0.1% ophthalmic suspension into the conjunctival sac every hour during the day and every two hours at night initially; after improvement, reduce to one drop every four hours, then one drop three to four times daily.
| Dosage form | OINTMENT |
| Renal impairment | No adjustment required for renal impairment as systemic absorption is minimal. |
| Liver impairment | No adjustment required for hepatic impairment as systemic absorption is minimal. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established; use not recommended. |
| Geriatric use | No specific geriatric dose adjustments; use same as adult dosing with caution due to potential increased intraocular pressure. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MAXIDEX (MAXIDEX).
| Breastfeeding | Corticosteroids enter breast milk in low concentrations; M/P ratio for dexamethasone is approximately 0.4. Theoretical risk of adrenal suppression in high doses. Use with caution, especially prolonged high-dose therapy. |
| Teratogenic Risk | Corticosteroids cross the placenta. First trimester: Increased risk of cleft lip/palate (OR 3.35). Second/third trimester: Fetal adrenal suppression, low birth weight, premature rupture of membranes. Avoid systemic use unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to dexamethasone or any component of the formulation.","Active ocular infections: untreated bacterial, fungal, viral (e.g., herpes simplex keratitis, vaccinia, varicella) or mycobacterial infections.","Corneal epithelial defects or ulcers."]
| Precautions | ["Prolonged use may cause elevated intraocular pressure (IOP), glaucoma, cataract formation, delayed wound healing, and secondary ocular infections.","Systemic absorption may occur with ophthalmic use, especially with prolonged therapy, leading to adrenal suppression.","Use with caution in patients with corneal thinning or epithelial defects to avoid perforation."] |
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| Monitor for maternal hyperglycemia, hypertension, adrenal suppression. Fetal: Ultrasound for growth restriction; consider fetal adrenal suppression if chronic use. Neonatal: Observe for hypoglycemia, adrenal insufficiency postpartum. |
| Fertility Effects | No direct evidence of altered fertility. May disrupt menstrual cycles via HPA axis suppression, potentially impacting ovulation. Long-term use may affect steroidogenesis. |