Bedside Snapshot

Use It For: Croup; asthma exacerbation; bacterial meningitis (with the first antibiotic) and vasogenic cerebral edema; antenatal steroids for threatened preterm birth at 24–34 weeks
Adult Dose: Asthma: 16 mg PO once daily for 2 days
Cerebral edema (brain metastases): 4–8 mg/day if mild; 16 mg/day or more if severe (e.g. 10 mg IV, then 4 mg IM every 6 hr)
Meningitis: 10 mg IV every 6 hr for 4 days
Pediatric Dose: Croup: 0.6 mg/kg PO/IM/IV once (max 16 mg); 0.15 mg/kg may be as effective but is less studied
Asthma (age 2 yr and older): 0.6 mg/kg PO once, or IV/IM if critically ill (max 16 mg)
Onset / Duration: PO/IV/IM: croup scores improve within about 2 hr; effect lasts ≥24 hr (once-daily regimens). Plasma T½ about 4 hr
Do Not Give / Hold If: Systemic fungal infection; hypersensitivity (some vials contain sulfite or benzyl alcohol); traumatic brain injury; cerebral malaria; IM route in immune thrombocytopenic purpura
Watch For: Hyperglycemia (glucose); hypokalemia (K⁺, ECG); delirium or steroid psychosis (mental status); masked infection (fever may be blunted)
Reversal / Rescue: No reversal agent: supportive care. Correct glucose and K⁺. Courses over 3–4 weeks: taper, and give stress-dose hydrocortisone for adrenal crisis
Must Remember: Dexamethasone never replaces epinephrine: nebulized epinephrine for stridor at rest, IM epinephrine for anaphylaxis. Adrenal crisis: hydrocortisone first; dexamethasone only if no other glucocorticoid is available.

Indications

Emergency & Prehospital

Croup (laryngotracheobronchitis): the first-line drug for children with croup, whatever the severity. Croup scores improve within 2 hr, and return visits and admissions drop. Moderate to severe croup (stridor at rest) also needs nebulized epinephrine (off-label)
Asthma exacerbation: a 1- or 2-dose oral course can stand in for 3–5 days of prednisone or prednisolone in children and adults. The label covers severe asthma. Short regimens are off-label
Severe allergic reaction or acute laryngeal edema: an adjunct only, given after IM epinephrine. The label names IM epinephrine as the drug of first choice. Steroids do not reliably prevent a biphasic anaphylactic reaction
High-altitude illness: used for moderate to severe acute mountain sickness and high-altitude cerebral edema (Wilderness Medical Society guideline). Descent matters most. Use oxygen when descent is not possible. Dexamethasone (NASEMSO v3.0): acute mountain sickness 4 mg IM, IV or PO every 6 hr until symptoms resolve (children 0.15 mg/kg every 6 hr, max 4 mg per dose); HACE 8 mg once, then 4 mg every 6 hr (children 0.15 mg/kg per dose every 6 hr). Give the dexamethasone with the descent. It does not replace it

ED / ICU / Transport

Suspected or proven bacterial meningitis: start the adjunct 10–20 min before the first antibiotic dose, or with it (e.g. ceftriaxone). The strongest evidence is in adult pneumococcal and pediatric Haemophilus influenzae type b (Hib) meningitis (off-label)
Vasogenic cerebral edema: a symptomatic brain tumor, metastases or neurosurgery (labeled). Not for traumatic brain injury. Metastatic spinal cord compression (MSCC) with neurological symptoms or signs: give it as soon as you can, before imaging if needed. Continue until surgery or radiotherapy (off-label)
Threatened preterm birth at 24–34 weeks: antenatal corticosteroid for fetal lung maturity when birth is likely within 7 days (off-label)
Hospitalized COVID-19 on oxygen or mechanical ventilation: lowers 28-day mortality; no benefit in patients without respiratory support. Acute respiratory distress syndrome (ARDS): the Society of Critical Care Medicine (SCCM) 2024 guideline conditionally recommends corticosteroids. It names no preferred agent or dose. Trial regimen (DEXA-ARDS, moderate-to-severe ARDS, started at 24 hr): dexamethasone 20 mg IV once daily days 1–5, then 10 mg once daily days 6–10. In that trial, ventilator-free days rose by 4.8 and 60-day mortality fell (21% vs 36%). Hyperglycemia hit 76% vs 70%. The trial stopped early (277 of 314 planned). This is not a guideline dose. ESICM 2023 makes no corticosteroid recommendation for ARDS (off-label)
Post-extubation stridor prevention: ventilated adults at high risk who fail a cuff-leak test should get systemic steroids at least 4 hr before extubation (ATS/ACCP 2017, conditional); agent and dose per ICU protocol
Acute migraine in the ED: one parenteral dose lowers the chance the headache comes back after discharge (American Headache Society 2016). It does not treat the headache you have now, so pair it with an acute migraine drug (off-label)

Other Uses

Antiemetic: one piece of multimodal prophylaxis for postoperative nausea and vomiting (PONV) and for chemotherapy-induced nausea and vomiting (CINV). Dose per the anesthesia or oncology protocol
Adrenal insufficiency: reach for hydrocortisone first. It is the labeled drug of choice. In primary adrenal insufficiency you also need a mineralocorticoid. In adrenal crisis, dexamethasone is the least-preferred alternative. Use it only when no other glucocorticoid is available
Labeled inflammatory, immune and diagnostic uses: allergic, rheumatic, dermatologic, ophthalmic, hematologic and neoplastic conditions, hypercalcemia of malignancy, multiple sclerosis flares (specialist use), and dexamethasone suppression testing for adrenocortical hyperfunction

Dosing & Administration

The doses below are E3's reviewed positions. Where a dose departs from the FDA label, the row tells you so. Follow your agency's protocols and medical direction.

Available Forms

Injection (dexamethasone sodium phosphate): 4 mg/mL in 1 mL (4 mg) and 5 mL (20 mg) vials; 10 mg/mL in 1 mL (10 mg) and 10 mL (100 mg) vials. The strength is written as dexamethasone phosphate. Concentrations vary by manufacturer. Your EMS or transport unit carries one of these, so confirm which before you draw up.
Excipients vary by manufacturer: some vials, in both 4 mg/mL and 10 mg/mL, contain sodium sulfite and benzyl alcohol. Preserved multiple-dose vials carry a preservative, often benzyl alcohol. Preservative-free single-dose vials exist. Check the vial.
Tablets: 0.25–6 mg (common strengths 0.5, 0.75, 1, 1.5, 2, 4 and 6 mg; strengths vary by manufacturer). Hemady 20 mg tablets are for multiple myeloma only.
Oral liquids: elixir 0.5 mg/5 mL; concentrate (Intensol) 1 mg/mL with a calibrated oral syringe.

Adult Dosing

Indication	Dose & Route	Repeat / Max	Notes
Asthma exacerbation	16 mg PO once daily	2 days (2 doses); max 16 mg/dose	At least as effective as prednisone 50 mg daily for 5 days in an ED trial of adults aged 18–45 yr. Give IV or IM when the patient cannot take PO, per protocol. In pregnancy, prednisone or prednisolone is usually preferred (see Special Populations).
Vasogenic cerebral edema (tumor, neurosurgery)	Brain metastases, mild symptoms: start 4–8 mg/day. Severe symptoms of raised ICP: 16 mg/day or more, e.g. the label regimen of 10 mg IV, then 4 mg IM every 6 hr	Titrate to symptoms: no fixed max; use the lowest effective dose	Congress of Neurological Surgeons (CNS) 2019: too little evidence to give steroids for asymptomatic metastases without mass effect; taper as rapidly as possible but no faster than clinically tolerated. Label: switch to PO (1–3 mg three times daily) as soon as possible and taper over 5–7 days. Never for traumatic brain injury.
Metastatic spinal cord compression with neurological symptoms or signs	16 mg PO (or the equivalent IV dose) as soon as possible, then 16 mg once daily	16 mg/day until surgery or the start of radiotherapy, then taper to stop	NICE 2023 regimen; US regimens vary, so follow oncology or neurosurgery direction. Stop if imaging rules out spinal metastases and MSCC. Never delay MRI or definitive treatment for the steroid.
Bacterial meningitis (adjunct)	Usual adult regimen: 10 mg IV every 6 hr (the dose used in the landmark adult trial). IDSA alternative: 0.15 mg/kg IV every 6 hr	Trial regimen: 10 mg/dose for 4 days (adult trial dose). IDSA: 2–4 days. The 10 mg per-dose cap is an E3 inference, not a sourced limit: IDSA states no per-dose cap (owner to confirm). 0.15 mg/kg would exceed 10 mg above about 67 kg	First dose 10–20 min before or with the first antibiotic; never delay antibiotics. Stop rules differ: IDSA continues only if Gram-positive diplococci or S. pneumoniae are found; NICE continues for pneumococcus or H. influenzae type b, stops for all other organisms (including meningococcus) and seeks infection specialist advice when no organism is found. Late start: IDSA does not start it after antibiotics; NICE gives it if within 12 hr of the first antibiotic.
Hospitalized COVID-19 on oxygen or ventilation	6 mg IV or PO once daily	Up to 10 days; max 6 mg/day	Mortality benefit with oxygen or invasive ventilation; no benefit (possible harm) without respiratory support.
ARDS (trial regimen, off-label)	20 mg IV once daily, days 1–5; then 10 mg IV once daily, days 6–10	10 days; max 20 mg/day	DEXA-ARDS trial, started 24 hr into moderate-to-severe ARDS. Not a guideline dose: SCCM 2024 names no agent or dose. Ventilator-free days +4.8; 60-day mortality 21% vs 36%; hyperglycemia 76% vs 70%.
Antenatal corticosteroids (24–34 weeks, birth likely within 7 days)	6 mg IM every 12 hr	4 doses (24 mg total); one repeat course only if ≥7 days since the first course and birth is again likely within 7 days	Start even if the full course may not finish before birth. Alternative: betamethasone 12 mg IM every 24 hr ×2. WHO: give only when there is no clinical evidence of maternal infection. US obstetric protocols differ on infection criteria and the gestational window, so follow OB direction.
Severe allergic reaction, laryngeal edema (adjunct)	Label schedule (acute self-limited allergic disorders): 4–8 mg IM on day 1, then a short oral taper over days 2–6	Single day-1 dose; then the taper above	Give IM epinephrine first. A steroid does not reverse airway edema, bronchospasm or shock in the first hours, and does not reliably prevent a biphasic reaction: observe as usual and treat any recurrence with epinephrine.

Pediatric Dosing

Indication	Dose (per kg) & Route	Max Single / Max Total	Notes
Croup (any severity)	0.6 mg/kg PO, IM or IV once	Max 16 mg; single dose	PO when the child can swallow; IM or IV if vomiting or unable. 0.15 mg/kg may be as effective but is less studied: no difference in 2-hr croup scores, return visits or need for epinephrine, but 0.6 mg/kg probably gave lower 24-hr croup scores (one small trial). 0.6 mg/kg is the NASEMSO dose (p. 156). Stridor at rest: add nebulized epinephrine.
Asthma exacerbation	Age 2 yr and older: 0.6 mg/kg PO (solution), or IV/IM if critically ill, once	Max 16 mg; single dose	Relapse rates similar to 3–5 days of prednisolone. Differs: GINA 2026 gives 0.3–0.6 mg/kg, max 12 mg, for total 1–2 days; some trials give 0.6 mg/kg daily for 2 days.
Bacterial meningitis (adjunct)	0.15 mg/kg IV every 6 hr	Max 10 mg per dose (E3 inference from the adult trial dose; IDSA states no cap; owner to confirm); 2–4 days (IDSA)	First dose 10–20 min before or with the first antibiotic. Continue if pneumococcus or Hib is found; stop for other organisms, such as meningococcus; no organism found: infection specialist advice (NICE). Strongest evidence in Hib meningitis; benefit in pediatric pneumococcal meningitis is uncertain. Age 28 days to 3 months: infection specialist advice (NICE gives it routinely only over 3 months); not routine in neonates.
Vasogenic cerebral edema	About 0.2 mg/kg/day in divided doses, preferably PO	Smallest effective dose; no fixed max: titrate to symptoms	Label guidance; neurosurgery or oncology directs the course.
Neonates	Not routinely used (consult): neonatal (NICU) dosing is specialist only	Specialist dosing only	Benefit to the newborn comes from the maternal antenatal course.

Weight-based dose checks: pediatric weight-based dosing.

Preparation & Administration

IV push: go slow. A rapid injection can trigger premature ventricular contractions (PVCs) in a stressed myocardium. Tell the patient that transient perineal (ano-genital) burning, tingling or itching can happen.
IM: the soluble phosphate ester still acts quickly when given IM. Skip IM in idiopathic thrombocytopenic purpura, where it is IV only.
Inspect: do not use a hazy solution or one with a precipitate.
PO: tablets or oral liquid; measure the concentrate only with its calibrated syringe.
Never epidural: not an approved route. Spinal cord infarction, paraplegia, stroke and death have been reported.

Dosing Notes: These doses match each other, oral or IV: dexamethasone 0.75 mg ≈ prednisone 5 mg ≈ methylprednisolone 4 mg ≈ hydrocortisone 20 mg. Kidney and liver issues are covered under Special Populations.

Contraindications & Precautions

Contraindications

Systemic fungal infection (unless needed to control a drug reaction)
Hypersensitivity to dexamethasone or a product component (sulfite, benzyl alcohol)
IM injection in idiopathic thrombocytopenic purpura
Cerebral malaria (avoid)
Live or live-attenuated vaccines: avoid during immunosuppressive doses

Precautions

Infection: hides the signs and raises the risk of any infection. Watch for latent tuberculosis, hepatitis B reactivation, Strongyloides hyperinfection (known or suspected infestation), and varicella or measles exposure in non-immune patients.
Diabetes: pushes glucose and insulin needs up.
Heart failure, hypertension, renal insufficiency: sodium and fluid build up, and potassium drops. Potassium loss is less than with hydrocortisone at equivalent doses.
Recent myocardial infarction: steroids are linked to left ventricular free-wall rupture.
Pheochromocytoma (suspected or known): systemic steroids can set off a pheochromocytoma crisis, and that crisis can be fatal. Weigh the risk before you give them.
GI disease: peptic ulcer, diverticulitis or a fresh anastomosis. Perforation signs may be minimal.
Psychiatric history, myasthenia gravis, ocular herpes simplex: mood or psychotic decompensation, acute weakness, corneal perforation.

Hold / Reassess If

Meningitis course: cerebrospinal fluid (CSF) not consistent with bacterial meningitis; an organism other than pneumococcus (IDSA, adults) or other than pneumococcus or Hib (NICE); no organism found (NICE: infection specialist advice)
New fever, hypotension or peritoneal signs: look for infection or perforation
Glucose above the institutional target despite insulin
New delirium, agitation or psychosis

Not for traumatic brain injury: Steroids do not help a head injury. They hurt. In the CRASH trial (10,008 adults with head injury), a 48-hr corticosteroid infusion raised 6-month mortality (25.7% vs 22.3%). Skip them for head injury. Older dexamethasone labeling lists head-injury cerebral edema, but the trial data say no.

Adverse Effects & Toxicity

Common

Hyperglycemia and higher insulin needs
Insomnia, mood swings, euphoria
Fluid retention, hypertension (less than with hydrocortisone)
Weight gain, hiccups
Leukocytosis: the steroid itself can raise the WBC, so judge infection on the whole picture
Transient perineal burning or itching after IV injection
With prolonged use: Cushingoid features, thin skin, poor wound healing, osteoporosis, aseptic (avascular) necrosis of the femoral and humeral heads, cataracts, growth suppression in children

Serious / Life-Threatening

Effect	Recognition	Management
Hyperglycemia	Rising glucose, polyuria; worse in diabetes and ICU patients	Check glucose; start or adjust insulin per protocol
Hypokalemia, hypokalemic alkalosis	Low K⁺, U waves, ectopy; worse with diuretics or amphotericin B	Replace K⁺; ECG if on digoxin
Infection (masked, opportunistic, reactivated)	Fever and peritoneal signs may be blunted; tuberculosis, hepatitis B, Strongyloides hyperinfection with gram-negative sepsis	Culture and treat; reduce or stop the steroid if possible
GI bleeding or perforation	Melena, falling hemoglobin, abdominal pain with few peritoneal signs	Resuscitate, imaging, surgical consult
Steroid psychosis, delirium	Insomnia, euphoria, agitation, hallucinations, severe depression	Safety measures, lowest effective dose, psychiatric input
Acute myopathy	Generalized weakness, including respiratory muscles, with neuromuscular blockers or myasthenia gravis; CK may rise	Minimize steroid and blocker exposure; recovery can take weeks to years
Anaphylactoid reaction	Rare; urticaria, bronchospasm, hypotension; sulfite-sensitive asthma	Stop; treat as anaphylaxis with IM epinephrine
Adrenal insufficiency after withdrawal	Hypotension, hypoglycemia, weakness during stress after a prolonged course	Stress-dose hydrocortisone. Courses longer than 3–4 weeks need a planned taper; shorter courses can usually stop without one

Overdose & Toxicity Management

Acute overdose: it is rarely dangerous. Expect hyperglycemia, hypokalemia, hypertension and agitation.
Management: supportive and symptomatic; check glucose and electrolytes.
Antidote: none.
Chronic excess: a Cushingoid state and adrenal suppression. Never stop a long course abruptly.

Monitoring

Parameter	When / How Often	Target / Act If
Clinical: croup or asthma response	Work of breathing, stridor, SpO₂ and peak flow before and after treatment	Stridor at rest or worsening distress: nebulized epinephrine (croup) or bronchodilators, and escalate; the steroid will not act in time
Clinical: neurologic status	Serial neuro checks in cerebral edema or meningitis	Falling level of consciousness or new deficit: imaging and neurosurgical review
Clinical: mental status	Every assessment, especially older adults and high doses	New delirium or psychosis: reassess dose and other causes
Clinical: BP, fluid balance, weight	During multi-day courses, more often in heart failure	Edema or rising BP: salt restriction, diuretic per protocol
Laboratory: glucose	Baseline in diabetes or critical illness, then regularly through the course	Glucose above target: insulin per protocol
Laboratory: potassium	Baseline and during multi-day courses, especially with diuretics, amphotericin B or digoxin	Low K⁺: replace; ECG if on digoxin
Laboratory: INR on warfarin	Frequently while the drugs are combined	Response to warfarin is usually reduced: adjust to the target INR
Infection surveillance	Temperature, WBC and cultures in prolonged or high-dose therapy	Fever may be blunted and WBC raised by the steroid itself: culture early
Ophthalmic	Intraocular pressure if therapy lasts more than 6 weeks	Raised pressure: ophthalmology review
Neonate after maternal therapy	Infants born to mothers who received substantial doses	Signs of hypoadrenalism: neonatal team evaluation

Interactions & Compatibility

Clinically Significant Interactions

Drug / Class	Effect	What To Do
Strong CYP3A4 inhibitors (itraconazole, ketoconazole, clarithromycin, ritonavir, cobicistat)	Raise dexamethasone exposure (itraconazole: AUC 3.7-fold)	Avoid if possible; otherwise watch for steroid adverse effects
Aprepitant (moderate CYP3A4 inhibitor)	Raises dexamethasone AUC about 2.2-fold	Expect a stronger effect; follow the antiemetic protocol's dexamethasone dose
CYP3A4 inducers (phenytoin, carbamazepine, phenobarbital, rifampin), ephedrine, cholestyramine	Lower dexamethasone exposure; phenytoin levels may rise or fall	A higher steroid dose may be needed; monitor seizure control and phenytoin levels
CYP3A4 substrates (e.g. indinavir, erythromycin)	Dexamethasone is a moderate CYP3A4 inducer and can lower their levels	Check the partner drug's labeling
Potassium-depleting drugs (loop and thiazide diuretics, amphotericin B), digoxin	Hypokalemia; arrhythmia risk with digoxin	Monitor K⁺ and ECG
Warfarin and other oral anticoagulants	Anticoagulant response usually reduced	Monitor INR closely
NSAIDs and aspirin	More GI ulceration and bleeding; salicylate clearance increased	Avoid the combination or add GI protection per protocol
Neuromuscular blockers; anticholinesterases in myasthenia gravis	Acute myopathy; severe weakness	Limit blocker duration; withdraw anticholinesterases 24 hr before starting if possible

Watch these too. Insulin and other antidiabetics: expect higher glucose. Vaccines: a weaker response, and live vaccines may replicate. Estrogens: higher steroid exposure. Cyclosporine: higher levels of both drugs, and seizures have been reported. Isoniazid: corticosteroids may lower its serum levels.

IV Compatibility

The label covers IV or IM injection. Give the IV dose as a slow push.
Some products contain sodium sulfite or benzyl alcohol. Check the vial when the patient has a sulfite allergy or is a neonate.
Verify with an institutional compatibility resource.

Special Populations

Pediatrics: croup and asthma are the main acute uses. The Pediatric Dosing table has the doses. Long courses slow growth, even at low doses. Track height, weight, blood pressure and intraocular pressure.
Neonates: babies whose mothers got substantial corticosteroid doses can end up with hypoadrenalism. Many vials, some single-dose ones included, contain benzyl alcohol. That is toxic to neonates. When a neonate needs dexamethasone, use a preservative-free product.
Pregnancy: dexamethasone crosses the placenta largely unchanged. The placenta inactivates far more cortisol and prednisolone than it does dexamethasone or betamethasone. That is why it is used for fetal lung maturity. For the mother's own problem, such as an asthma exacerbation, a non-fluorinated steroid (prednisone, prednisolone, methylprednisolone or hydrocortisone) is usually preferred. Never hold steroid treatment for a clear maternal indication. Use dexamethasone where it is the indicated agent (bacterial meningitis, antenatal course). Orofacial clefts, intrauterine growth restriction and lower birth weight are reported with maternal corticosteroid use. Animal studies show cleft palate. Steroids raise maternal glucose, so pair them with glucose control in diabetes.
Lactation: it passes into breast milk and could suppress infant growth or adrenal function. A short emergency course is no reason to withhold treatment. For high-dose, prolonged therapy, the multiple-myeloma labeling advises no breastfeeding during treatment and for 2 weeks after the last dose.
Older Adults: start at the low end of the dose range. Diabetes, fluid retention and hypertension are more likely in this group.
Renal Impairment: less than 10% leaves in the urine, and no dose adjustment has been established. Watch for fluid retention and hypokalemia.
Hepatic Impairment: cirrhosis slows metabolism, so the effect is stronger. The label gives no adjustment. Use the lowest effective dose.
Obesity / Dosing Weight: adult doses are fixed, not weight-based. Pediatric doses are per kg up to the adult cap.
Thyroid Disease: clearance drops in hypothyroidism and climbs in hyperthyroidism. Reassess the dose whenever thyroid status changes.

Field & Transport Considerations

Scope: Paramedic, RN and critical-care transport. Many EMS croup and asthma protocols carry it. It varies by state and agency protocol.
Storage & Stability: 20–25°C (68–77°F). Keep it in the carton, out of the light and away from freezing. The solution is heat-sensitive, so limit how much heat it sees in the vehicle. Discard it if hazy or precipitated.
Carried Concentration: the 4 mg/mL and 10 mg/mL vials look alike. A 16 mg dose is 4 mL of 4 mg/mL, but 1.6 mL of 10 mg/mL. Read the label out loud and state the volume.
Name Confusion: dexamethasone and dexmedetomidine are an ISMP confused-name pair. The mix-up swaps a steroid for a sedative infusion.
Interfacility Transport: antenatal course: time of each dose and when the next is due; meningitis: time of the first steroid dose relative to the first antibiotic; COVID-19 or ARDS: day of the course.
Handoff Essentials: dose (mg), route, time, indication, planned number of doses or taper, latest glucose and K⁺.

Clinical Pearls

A steroid does not open the airway now: Croup scores start to improve about 2 hr after dexamethasone. Stridor at rest needs nebulized epinephrine now. In croup, the steroid helps later by cutting return visits. Anaphylaxis needs IM epinephrine. Steroids won't reliably stop a biphasic reaction. Watch until symptoms have fully resolved, and make sure there is an epinephrine auto-injector plan.

Croup: treat every severity: Mild croup gets dexamethasone too. It cuts return visits and admissions. If the child can swallow, use the oral route. An injection adds distress to an airway that is already narrowed.

Exam discriminator: which steroid?:

Dexamethasone: about 25 times the glucocorticoid punch of hydrocortisone, with almost no salt-retaining effect. It acts once a day. Think croup, cerebral edema, meningitis and the antenatal course.
Hydrocortisone: glucocorticoid and salt-retaining (mineralocorticoid) effect both. Think adrenal crisis and septic shock.
Pregnancy: dexamethasone reaches the fetus, which is why it matures the lungs. For the mother's own illness, use prednisone or prednisolone.

Adrenal crisis needs hydrocortisone: Hydrocortisone 100 mg IV or IM is the drug of choice. Dexamethasone lacks the salt-retaining effect that primary adrenal failure needs. No hydrocortisone on hand? Give another glucocorticoid. Dexamethasone is the least-preferred option, but never delay treatment.

Meningitis: steroid with the antibiotic, never instead of it: Draw the dexamethasone up with the first antibiotic dose. Never hold the antibiotic while you hunt for it.

Short asthma courses fix adherence: One or two oral doses match a 3–5 day prednisone or prednisolone course for relapse. A single dose is finished before the patient leaves the ED. A 2-day regimen needs only one take-home dose.

COVID-19: oxygen is the trigger: Dexamethasone cut mortality only in hospitalized patients on oxygen or invasive ventilation. Patients without respiratory support did not benefit, and they may be harmed.

Pharmacology

Mechanism of Action

It binds intracellular glucocorticoid receptors, which changes gene transcription. The result is suppressed inflammatory and immune responses.
It reduces airway mucosal and peritumoral (vasogenic) edema, so you get less stridor and lower intracranial pressure over hours to days.
At equivalent anti-inflammatory doses, it has almost no mineralocorticoid (sodium-retaining) effect. That makes it a poor substitute for hydrocortisone in primary adrenal failure.
Given to the mother before preterm birth, it speeds fetal lung maturation.

Pharmacokinetics

Route	Onset	Peak	Duration
IV	Clinical effect within hours (croup scores improve by 2 hr)	Plasma: end of injection	≥24 hr (once-daily regimens)
IM	Rapid (soluble phosphate ester)	—	≥24 hr
PO	Clinical effect within hours (croup scores improve by 2 hr)	Plasma: 1 hr (range 0.5–4 hr)	≥24 hr (once-daily regimens)

Half-life: plasma T½ is about 4 hr. The biologic effect lasts far longer. That is why once-daily and single-dose regimens work.
Metabolism: the liver does it through CYP3A4. Dexamethasone is also a moderate CYP3A4 inducer.
Elimination: less than 10% excreted unchanged in urine.
Protein binding: about 77%.
Potency: 0.75 mg is equivalent to 20 mg hydrocortisone or 5 mg prednisone.

Names & Classification

Generic Name: Dexamethasone (injection: dexamethasone sodium phosphate)
Brand Names: Decadron (brand discontinued in the US; generics widely available); Hemady (20 mg tablets for multiple myeloma); Dexamethasone Intensol (oral concentrate)
Pharmacologic Class: Long-acting synthetic glucocorticoid
Therapeutic Class: Anti-inflammatory and immunosuppressant corticosteroid
Controlled Substance: Not controlled
ISMP High-Alert: No
Look-Alike / Sound-Alike: dexAMETHasone / dexmedeTOMIDine (ISMP confused drug names list)

References

Fresenius Kabi USA. (2026). Dexamethasone sodium phosphate injection, USP [prescribing information] (revised March 2026); and Edenbridge Pharmaceuticals. (2026). Hemady (dexamethasone) tablets [prescribing information] (pharmacokinetics, pregnancy, lactation and drug interactions); and Hikma Pharmaceuticals USA. (2026). Dexamethasone sodium phosphate injection, USP, 4 mg/mL and 10 mg/mL [prescribing information] (concentrations and excipients); and Major Pharmaceuticals. (2026). Dexamethasone tablets, USP (4 mg and 6 mg) [prescribing information] (drug interactions, including CYP3A4 induction; allergic-disorder dosing schedule). DailyMed, National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cca2c160-9188-48e8-9505-49a52388dcb7 ; https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6b9cf32c-6d60-4853-bbfd-2304ffc2c129 ; https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=0277cc0a-2fd4-4605-a310-b613be84ee26 ; https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=64b46398-9b97-45e8-b1ba-1a202d574448
Aregbesola, A., Tam, C. M., Kothari, A., Le, M. L., Ragheb, M., & Klassen, T. P. (2023). Glucocorticoids for croup in children. Cochrane Database of Systematic Reviews, 1(1), CD001955. doi:10.1002/14651858.CD001955.pub5. https://pmc.ncbi.nlm.nih.gov/articles/PMC9831289/
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Dexamethasone (Decadron)