Can I give 5 mg of Decadron (dexamethasone) intramuscularly to a 17‑year‑old patient weighing 101 lb?

Can You Give 5 mg Decadron IM to a 17-Year-Old Weighing 101 lb?

Yes, 5 mg of dexamethasone IM is a safe and appropriate dose for a 17-year-old patient weighing 101 lb (45.9 kg), falling well within established dosing parameters for most indications. This dose represents approximately 0.11 mg/kg, which is below the typical therapeutic range for most acute conditions but may be appropriate for specific indications like antiemesis or mild inflammatory conditions.

Dose Calculation and Safety Assessment

Your patient weighs 101 lb (45.9 kg), and the proposed 5 mg dose equals approximately 0.11 mg/kg. 1

Weight-Based Dosing Context:

• Standard therapeutic range: Most acute conditions require 0.15–0.6 mg/kg 2, 1
• Your proposed dose (0.11 mg/kg) sits below this range but remains safe
• Maximum safe single dose: Up to 9 mg/day for routine use, with higher doses (up to 10 mg every 6 hours) reserved for life-threatening conditions 1, 3

For a 45.9 kg patient, typical dose ranges would be:

• Low-dose therapy: 6.9–9.2 mg (0.15–0.2 mg/kg) 2
• Moderate-dose therapy: 13.8–27.5 mg (0.3–0.6 mg/kg) 4, 5
• High-dose therapy: Up to 40 mg for specific severe conditions 1

Indication-Specific Guidance

The appropriateness of 5 mg depends entirely on your clinical indication:

Antiemesis (Chemotherapy/Radiation)

• Standard dose: 4 mg oral or IV 3
• Your 5 mg dose is appropriate and slightly above standard, providing adequate coverage 3

Allergic Reactions (Non-Anaphylactic)

• Recommended range: 1–2 mg/kg = 45.9–91.8 mg for this patient 6
• Your 5 mg dose is significantly subtherapeutic for acute allergic reactions 6
• Critical: Epinephrine 0.01 mg/kg IM (0.46 mg, rounded to 0.5 mg) is first-line for anaphylaxis, not dexamethasone 6

Asthma Exacerbations

• Effective dose range: 0.15–0.6 mg/kg = 6.9–27.5 mg 4, 7, 5
• Your 5 mg dose is below therapeutic range for acute asthma 4, 7
• Evidence-based recommendation: Use 0.6 mg/kg (27.5 mg) IM as single dose, equivalent to 5-day prednisone course 5

Croup

• Effective dose: 0.15 mg/kg = 6.9 mg, with benefit evident by 30 minutes 8
• Your 5 mg dose is slightly subtherapeutic but may provide partial benefit 8

Bacterial Meningitis

• Required dose: 0.15 mg/kg every 6 hours = 6.9 mg per dose 3, 2
• Your 5 mg dose is inadequate for this life-threatening condition 3
• Timing critical: Must give 10–20 minutes before first antibiotic dose 3, 2

Perioperative Use (Tonsillectomy)

• Standard dose: 0.15–0.5 mg/kg = 6.9–23 mg 3
• Your 5 mg dose is at the low end but acceptable for PONV prophylaxis 3

Route Considerations

IM administration is appropriate for this patient and dose. 1

• Bioequivalence: IV and oral routes are 1:1 equivalent; IM absorption is reliable 2, 1
• Injection site: Use mid-outer thigh for IM injection 6
• Maximum per site: Do not exceed 150 mg per injection site (not relevant at 5 mg dose) 3

Critical Safety Considerations

Adolescent-Specific Factors:

• At 17 years old, this patient should be dosed as an adult for most indications 3
• No dose adjustment needed for adolescent age alone 1

Monitoring Requirements:

• Observe for at least 15 minutes post-injection 6
• Monitor blood pressure, glucose if diabetic 3
• For severe conditions requiring repeat dosing, monitor for hyperglycemia, hypertension 3

Contraindications to Consider:

• Active systemic infection (unless treating specific conditions like bacterial meningitis) 3
• Uncontrolled diabetes mellitus 3
• Known hypersensitivity to dexamethasone 1

When NOT to Use 5 mg:

If treating acute severe conditions (anaphylaxis, severe asthma, bacterial meningitis), 5 mg is inadequate—you need 7–28 mg depending on indication. 3, 6, 4, 5

Tapering Requirements

No taper needed for a single 5 mg dose. 2

• Tapering only required for doses ≥8 mg/day for >5 days 2
• Single-dose or short courses (3–4 days) can be stopped abruptly 2

Common Pitfalls to Avoid

1. Underdosing severe conditions: Don't use 5 mg for anaphylaxis, severe asthma, or bacterial meningitis—these require higher doses 3, 6, 4
2. Delaying epinephrine: If anaphylaxis is suspected, give epinephrine first, not dexamethasone 6
3. Assuming oral compliance: IM route ensures medication delivery, particularly valuable in vomiting patients or those with poor adherence 4, 7
4. Ignoring indication-specific timing: For bacterial meningitis, dexamethasone must precede antibiotics by 10–20 minutes 3, 2