Clinical safety rating: safe
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Betamethasone is a glucocorticoid receptor agonist that binds to the glucocorticoid receptor, leading to modulation of gene expression, resulting in anti-inflammatory and immunosuppressive effects. It also suppresses the hypothalamic-pituitary-adrenal axis.
| Metabolism | Hepatic metabolism primarily via CYP3A4. |
| Excretion | Primarily renal: ~60% as metabolites, <5% unchanged. Biliary/fecal: ~15-20%. |
| Half-life | Terminal half-life: 6.4 hours (range 4.3-9.4 hours). Clinically, adrenal suppression lasts 2.7-3.5 days after single dose. |
| Protein binding | ~64% bound, primarily to albumin and corticosteroid-binding globulin (CBG). |
| Volume of Distribution | Vd: 1.4-1.8 L/kg. Clinical meaning: extensive tissue distribution, exceeding total body water. |
| Bioavailability | Oral: ~100%; Rectal: ~50%; Topical: <1% (systemic absorption minimal). |
| Onset of Action | Oral: 1-2 hours; IM: 6-12 hours; IV: rapid (within minutes); Topical: 2-4 hours. |
| Duration of Action | Duration: 3-4 days after single dose; adrenal suppression persists 2.7-3.5 days. IM: 6-14 days. |
| Molecular Weight | 392.46 Da |
0.6 to 9 mg/day orally in divided doses; intramuscularly, 0.5 to 9 mg/day; intravenously, up to 12 mg/day; topical (as valerate or dipropionate) applied thinly to affected area once to twice daily.
| Renal impairment | No specific GFR-based dose adjustments required; use with caution in severe renal impairment. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use or reduce dose by 75%. |
| Pediatric use | Oral: 0.0175 to 0.25 mg/kg/day in 3-4 divided doses; IM: 0.0175 to 0.125 mg/kg/day every 24-48 hours; topical: apply sparingly once to twice daily for short durations. |
| Geriatric use | Initiate at lower end of dosing range due to increased risk of osteoporosis, hyperglycemia, and immunosuppression; monitor for adverse effects. |
| 1st trimester | Use only if potential benefit justifies risk; associated with cleft palate in animal studies, but human data limited. Avoid systemic use if possible. |
| 2nd trimester | May be used with caution; monitor fetal growth with prolonged use. Risk of adrenal suppression in neonate if used near term. |
| 3rd trimester | Use with caution; prolonged use may cause neonatal adrenal suppression. Avoid high doses or prolonged treatment. Single course of betamethasone for fetal lung maturity is standard. |
Clinical note
Standard of care for fetal lung maturation in anticipated preterm delivery between 24 0/7 and 36 6/7 weeks gestation. A single course of betamethasone (two IM doses of 12 mg given 24 hours apart) reduces rates of RDS, IVH, NEC, and neonatal death. Penetrates the placenta without inactivation by 11β-HSD2 (unlike prednisone). Repeat courses are not recommended routinely due to potential effects on fetal brain and growth.
| Placental transfer | Betamethasone crosses the placenta. The placental transfer is moderate; the fetal concentration is approximately 30% of maternal concentration after maternal administration. |
■ FDA Black Box Warning
None.
| Serious Effects |
Systemic fungal infectionHypersensitivity to betamethasone or any component of the formulationAdministration of live or live-attenuated vaccines (immunosuppressive doses)
| Precautions | Immunosuppression: increased risk of infections, Adrenal suppression: may require dose adjustment during stress, Osteoporosis: long-term use increases fracture risk, Gastrointestinal perforation: increased risk in patients with GI disease, Growth suppression in children, Cushing's syndrome with prolonged use, Psychiatric disturbances: including euphoria, depression, psychosis, Monitor blood pressure, blood glucose, and electrolyte levels |
| Food/Dietary | Avoid grapefruit and grapefruit juice with oral betamethasone due to CYP3A4 inhibition, which can increase corticosteroid levels and risk of side effects. No specific food restrictions with topical or injectable forms, but a low-sodium diet is recommended during prolonged systemic therapy to minimize fluid retention and hypertension. |
Loading safety data…
| Breastfeeding | Enters breast milk in low amounts; unlikely to cause adverse effects in infant at maternal doses up to 10 mg/day. However, avoid high doses or prolonged use. Monitor infant for adrenal suppression if mother is on prolonged high-dose therapy. |
| Lactation Rating | L2 (limited data - probably compatible) |
| Teratogenic Risk | Betamethasone is a corticosteroid; in animal studies, it has been associated with increased risk of cleft palate at high doses. In humans, systemic use during first trimester may be associated with a small increased risk of oral clefts (odds ratio ~1.3-1.5). Second/third trimester use does not appear teratogenic but may cause fetal adrenal suppression, intrauterine growth restriction, and preterm birth with prolonged use. Betamethasone is used antenatally to accelerate fetal lung maturity (two doses of 12 mg IM, 24 hours apart) without evidence of teratogenicity at this regimen. |
| Fetal Monitoring | Monitor maternal blood pressure, blood glucose (corticosteroids can cause hyperglycemia), and signs of infection. Fetal monitoring includes serial ultrasound for growth restriction if used long-term. When used for fetal lung maturity, no specific monitoring beyond routine antenatal care. Watch for maternal adrenal suppression if therapy exceeds 2 weeks. |
| Fertility Effects | Betamethasone has no established direct effect on fertility. Chronic use may suppress the hypothalamic-pituitary-adrenal axis and alter menstrual cycle regularity, potentially impairing ovulation. Use at high doses may cause reversible amenorrhea. No evidence of permanent fertility impairment. |
| Clinical Pearls | Betamethasone is a potent corticosteroid with 25 times the anti-inflammatory potency of hydrocortisone. For acute asthma exacerbations, intramuscular betamethasone acetate and sodium phosphate provides rapid onset with sustained effect. In preterm labor, betamethasone is preferred over dexamethasone for fetal lung maturation due to lower incidence of periventricular leukomalacia. Avoid intra-articular injection in unstable joints or infections. Taper dosing after prolonged systemic use to prevent adrenal insufficiency. |
| Patient Advice | Do not stop taking this medication abruptly without consulting your doctor, as it may cause withdrawal symptoms. · Avoid exposure to infections; contact your doctor if you develop fever or illness. · Inform all healthcare providers that you are taking betamethasone before any surgery or vaccination. · Take with food or milk to reduce gastrointestinal irritation. · Do not drink grapefruit juice while on this medication if taking oral formulations, as it may increase side effects. · Report unusual weight gain, swelling, mood changes, or vision problems to your doctor. |