METHYLPREDNISOLONE ACETATE
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.
Methylprednisolone acetate is a synthetic glucocorticoid that binds to the glucocorticoid receptor, modulating gene expression to suppress inflammation, immune response, and adrenal function. It inhibits phospholipase A2, reduces prostaglandin and leukotriene synthesis, and decreases cytokine production.
| Metabolism | Hepatic metabolism via CYP3A4; also metabolized by 11β-hydroxysteroid dehydrogenase and other pathways. |
| Excretion | Renal: <10% unchanged; extensive hepatic metabolism to inactive metabolites primarily excreted renally as glucuronides and sulfates. |
| Half-life | Terminal half-life: 3-3.5 hours; correlates with duration of anti-inflammatory effect due to receptor-mediated action. |
| Protein binding | ~77% bound to albumin and corticosteroid-binding globulin (transcortin). |
| Volume of Distribution | Vd: 1-1.2 L/kg; indicates extensive tissue distribution including synovium. |
| Bioavailability | IM: 100% after methylprednisolone acetate suspension; Intra-articular: 100% locally; Oral: not applicable (acetate form). |
| Onset of Action | Intra-articular/soft tissue injection: 6-48 hours; IM: 24-48 hours; Topical: variable, typically within days. |
| Duration of Action | Intra-articular: 1-4 weeks depending on dose and joint; IM: 6-12 days; Topical: weeks with tapering. |
| Molecular Weight | 416.51 |
40-80 mg intramuscular (IM) or intra-articular (IA) injection; for IM use, dose may be repeated every 1-4 weeks as needed. Maximum single IM dose: 120 mg.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for any degree of renal impairment, including end-stage renal disease. |
| Liver impairment | No specific dose adjustment guidelines based on Child-Pugh class; use with caution in severe hepatic impairment due to risk of adverse effects. |
| Pediatric use | 0.03-2 mg/kg/day IM or IA; alternatively, 1-4 mg/kg/day for 3-7 days depending on indication. Maximum dose: 120 mg. |
| Geriatric use | Start at lower end of dosing range (40-80 mg IM/IA) due to increased risk of osteoporosis, hyperglycemia, and infections; monitor closely. |
| 1st trimester | Associated with cleft palate (1-2% risk) with first trimester exposure; use only if benefit outweighs risk. |
| 2nd trimester | May cause fetal adrenal suppression; use if clearly needed. |
| 3rd trimester | May cause neonatal adrenal suppression; use if clearly needed. |
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 form. Fetal levels are about 50% of maternal levels. |
| Breastfeeding |
■ FDA Black Box Warning
Methylprednisolone acetate is not for intrathecal or epidural administration. Inadvertent injection into the dural sac may result in arachnoiditis, meningitis, paraparesis, or death.
| Common Effects | immunosuppression |
| Serious Effects |
Systemic fungal infectionHypersensitivity to methylprednisolone or any excipientAdministration of live or live attenuated vaccines (due to immunosuppression)
| Precautions | May mask signs of infection; avoid in active infections unless specific antimicrobial therapy is given., Prolonged use may lead to adrenal suppression; taper dose gradually after long-term therapy., Increased risk of osteoporosis with long-term use., May cause gastrointestinal bleeding; use cautiously in patients with peptic ulcer disease., May exacerbate psychiatric conditions; caution in patients with emotional instability or psychotic tendencies., May increase blood pressure and sodium retention; monitor for edema and hypertension., May decrease bone density; use lowest effective dose for shortest duration. |
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| Enters breast milk in low levels; use with caution, especially with high doses. Monitor infant for growth and adrenal suppression. |
| Lactation Rating | L2 – Safer |
| Teratogenic Risk | First trimester: Increased risk of cleft lip and palate (odds ratio ~1.3-3.3) with systemic use. Second/third trimester: Potential for fetal adrenal suppression, intrauterine growth restriction (IUGR), and premature birth with prolonged high-dose use. Avoid use near term due to risk of neonatal adrenal insufficiency. |
| Fetal Monitoring | Monitor maternal blood pressure, blood glucose (gestational diabetes risk), and signs of infection. Fetal monitoring: serial ultrasound for growth restriction if prolonged use; consider neonatal evaluation for adrenal suppression if used near delivery. |
| Fertility Effects | No direct evidence of impaired fertility; may suppress ovulation at high doses via hypothalamic-pituitary-adrenal axis inhibition, reversible upon discontinuation. |
| Food/Dietary | Avoid grapefruit and grapefruit juice (potential CYP3A4 interaction). Limit sodium intake to reduce fluid retention. Increase calcium and vitamin D intake to counteract bone loss. Avoid alcohol (increases gastric irritation risk). |
| Clinical Pearls | Synthetic glucocorticoid with high potency; avoid intra-articular injection into unstable joints. Taper dose after prolonged therapy (≥3 weeks) to avoid adrenal crisis. Monitor for iatrogenic Cushing's syndrome, hyperglycemia, and osteoporosis. Local injection can cause post-injection flare (crystal-induced synovitis). Not for intrathecal use (risk of arachnoiditis). |
| Patient Advice | Do not stop taking this medication abruptly; follow your doctor's tapering schedule. · Report signs of infection (fever, sore throat) or mood changes. · Avoid live vaccines during treatment. · Use with caution if you have diabetes, high blood pressure, or osteoporosis. · May cause increased appetite, weight gain, and fluid retention. |