DEXAMETHASONE SODIUM PHOSPHATE
Clinical safety rating: avoid
CYP3A4 inducers (eg phenytoin) may decrease efficacy and inhibitors may increase effects Can cause hyperglycemia and adrenal suppression with prolonged use.
Dexamethasone sodium phosphate is a glucocorticoid that binds to the glucocorticoid receptor, leading to anti-inflammatory and immunosuppressive effects by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis, and modulating gene expression.
| Metabolism | Primarily hepatic via CYP3A4; also undergoes 5α-reductase and 5β-reductase metabolism. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for approximately 60-70% of elimination; biliary/fecal excretion accounts for 30-40%. |
| Half-life | Terminal elimination half-life is 3-4 hours in adults; however, the duration of action extends beyond the plasma half-life due to intracellular receptor-mediated effects. |
| Protein binding | Approximately 77-84% bound, primarily to albumin and corticosteroid-binding globulin. |
| Volume of Distribution | Apparent volume of distribution is 0.8-1.0 L/kg, indicating distribution into total body water and extensive tissue penetration. |
| Bioavailability | Oral bioavailability is approximately 80-90%; intramuscular bioavailability is virtually 100%. |
| Onset of Action | Intravenous: rapid (within minutes); intramuscular: 30-60 minutes; oral: 1-2 hours. |
| Duration of Action | Duration of action is 24-72 hours depending on dose and route; the biological half-life is longer than plasma half-life due to glucocorticoid receptor binding and downstream effects. |
| Molecular Weight | 516.4 |
4-20 mg IV or IM every 4-6 hours; for cerebral edema: 10 mg IV followed by 4 mg IM/IV every 6 hours; for shock: 20 mg IV initially then 2-6 mg/kg IV bolus or 40 mg IV every 2-6 hours as needed.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment for GFR; use caution in severe renal impairment (e.g., GFR <30 mL/min) due to potential fluid retention; monitor electrolytes. |
| Liver impairment | Child-Pugh A or B: no dose adjustment; Child-Pugh C: reduce dose by 50% or use with caution due to impaired metabolism. |
| Pediatric use | 0.15-0.3 mg/kg/day IV/IM divided every 6-12 hours; for cerebral edema: loading dose 1-2 mg/kg IV then 1-1.5 mg/kg/day divided every 4-6 hours; maximum 16 mg/day. |
| Geriatric use | Start at lower end of adult dosing (e.g., 2-4 mg IV/IM every 6 hours); monitor for hyperglycemia, fluid retention, and osteoporosis; adjust based on renal function. |
| 1st trimester | Use only if clearly needed due to risk of oral clefts (approx. 0.1% absolute risk increase) and potential for adrenal suppression. Avoid high doses. |
| 2nd trimester | Use with caution; may cause fetal adrenal suppression, growth restriction, and preterm delivery. Monitor for maternal hyperglycemia. |
| 3rd trimester | Use with caution; risk of neonatal adrenal suppression, low birth weight, and premature closure of ductus arteriosus. Infants require monitoring for adrenal insufficiency. |
Clinical note
CYP3A4 inducers (eg phenytoin) may decrease efficacy and inhibitors may increase effects Can cause hyperglycemia and adrenal suppression with prolonged use.
| FDA category | Positive |
| Placental transfer | Readily crosses placenta; metabolized to active dexamethasone. Approximately 75% of maternal concentration found in fetal circulation. |
■ FDA Black Box Warning
None.
| Common Effects | immunosuppression |
| Serious Effects |
Systemic fungal infectionHypersensitivity to dexamethasone or any componentAdministration of live or live-attenuated vaccines (due to immunosuppression)
| Precautions | Increased risk of infection due to immunosuppression, Adrenal suppression with prolonged use, Osteoporosis with long-term use, Gastrointestinal perforation or ulceration, Corticosteroid-induced myopathy, Neuropsychiatric effects including mood swings and psychosis, Cushing's syndrome with prolonged therapy, Growth suppression in children, Ocular effects such as glaucoma and cataracts, Cardiovascular effects including hypertension and fluid retention |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they may increase dexamethasone levels. Limit sodium intake (e.g., salty snacks, processed foods) to reduce fluid retention. Increase potassium-rich foods (bananas, oranges, spinach) if hypokalemia develops. Alcohol may increase risk of GI irritation and ulceration; avoid during high-dose therapy. |
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| Breastfeeding | Enters breast milk in low concentrations. Doses up to 8 mg/day are considered compatible with breastfeeding. Prolonged high doses may suppress infant adrenal function or growth. Monitor infant for signs of adrenal suppression (e.g., poor feeding, vomiting, lethargy). |
| Lactation Rating | L2 (Safer) |
| Teratogenic Risk | First trimester: Increased risk of cleft palate (odds ratio 3.4). Second/third trimesters: Fetal adrenal suppression, intrauterine growth restriction, premature birth. Chronic therapy: Additive risk of maternal hypertension, gestational diabetes, preterm birth. |
| Fetal Monitoring | Maternal: Blood pressure, glucose tolerance testing (24-28 weeks), weight gain, signs of infection. Fetal: Serial ultrasound for growth, amniotic fluid index; consider fetal adrenal axis assessment if prolonged use. |
| Fertility Effects | High doses may inhibit ovulation and delay conception. No permanent effect on fertility in prospective studies; dose-dependent reversible disruption of menstrual cyclicity. |
| Clinical Pearls | Dexamethasone sodium phosphate is a high-potency corticosteroid with negligible mineralocorticoid activity; ideal for cerebral edema due to its excellent CNS penetration. For acute exacerbations of multiple sclerosis, use high-dose IV (e.g., 30 mg/day for 3 days) followed by oral taper. Rapid IV administration can cause perineal itching; slow infusion over 10-15 minutes. Monitor blood glucose frequently, as hyperglycemia is common even in non-diabetics. Do not use in active infections without appropriate antimicrobial coverage due to immunosuppression. |
| Patient Advice | Do not stop taking this medicine suddenly; the dose must be tapered under your doctor's guidance to avoid adrenal crisis. · Report any signs of infection (fever, sore throat, cough) promptly as this drug lowers your immune response. · Avoid live vaccines (e.g., MMR, nasal flu) while on this medication. · If you have diabetes, monitor your blood sugar closely; your diabetes medication dose may need adjustment. · Take with food or milk to reduce stomach upset; do not take on an empty stomach. |