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. |
| Molecular Weight | 392.46 |
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 | Avoid. Corticosteroids are associated with increased risk of orofacial clefts (odds ratio ~3.35) when used in first trimester. However, if necessary for maternal condition, use lowest effective dose. |
| 2nd trimester | Use caution. May cause fetal growth restriction, adrenal suppression, and increased risk of preterm delivery. Monitor fetal growth. |
| 3rd trimester | Use caution. Prolonged use may lead to neonatal adrenal suppression. Monitor neonate for signs of adrenal insufficiency. |
Clinical note
Comprehensive clinical and safety monograph for MAXIDEX (MAXIDEX).
| Placental transfer | Dexamethasone readily crosses the placenta. About 76% of maternal concentration is achieved in fetal circulation. It is not extensively metabolized by placenta, leading to significant fetal exposure. |
| Breastfeeding | Dexamethasone is excreted into breast milk in small amounts. After a single dose, the milk-to-plasma ratio is about 0.15. Potential for adrenal suppression in the infant if maternal doses are high or prolonged. Use lowest effective dose for shortest duration. Consider waiting 3-4 hours after dose to breastfeed. |
■ FDA Black Box Warning
None
| Serious Effects |
Systemic fungal infectionHypersensitivity to dexamethasone or any componentAdministration of live or live-attenuated vaccines (due to immunosuppression)Idiopathic thrombocytopenic purpura (for ophthalmic use of Maxidex)
| 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. |
| Food/Dietary | No significant food interactions. However, grapefruit juice may increase systemic dexamethasone levels if large amounts are ingested, though ophthalmic use is minimal. No dietary restrictions required. |
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| Lactation Rating | L3 (Moderately Safe) - Limited data suggest potential for adverse effects but generally compatible with breastfeeding with caution. |
| 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 | 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. |
| Clinical Pearls | Maxidex (dexamethasone 0.1%) is a potent corticosteroid ophthalmic suspension. Use with caution in patients with corneal epithelial defects or stromal thinning due to risk of delayed healing and perforation. Monitor intraocular pressure (IOP) closely; >40% of patients may develop significant IOP elevation, especially in known steroid responders. Taper dose rather than abrupt discontinuation to avoid rebound inflammation. Contraindicated in epithelial herpes simplex keratitis (dendritic keratitis), fungal infections, and mycobacterial infections. Not for use in ocular hypertension or glaucoma. |
| Patient Advice | Shake the bottle well before each use to ensure uniform suspension. · Do not touch the dropper tip to your eye or any surface to avoid contamination. · Remove contact lenses before instillation and wait at least 15 minutes before reinserting. · Apply gentle pressure to the inner corner of the eye (nasolacrimal occlusion) for 1-2 minutes after each drop to minimize systemic absorption. · Report any eye pain, redness, light sensitivity, vision changes, or discharge immediately. · Do not use this medication for longer than prescribed; prolonged use can increase eye pressure and risk of cataracts. · If you have diabetes, monitor blood glucose more frequently as systemic absorption can raise blood sugar. · Avoid stopping the medication suddenly without consulting your doctor to prevent inflammation recurrence. |