Cah Infant Hydrocortisone Dosing

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name: cah-infant-hydrocortisone-dosing
description: Calculate and prescribe oral hydrocortisone replacement in infants and young children with classical congenital adrenal hyperplasia (21-hydroxylase deficiency, SW or SV) — including dose (mg/m²/day), schedule, formulation, route, choice of agent, and what NOT to use. Use when a clinician asks "what dose of hydrocortisone for a CAH baby", "starting hydrocortisone for a newborn with CAH", "how to split the hydrocortisone schedule in CAH", "can I use prednisolone or dexamethasone in a CAH infant", "how to prepare hydrocortisone for an infant", or any initiation/maintenance dosing question for classical CAH in children under 12 years. Source: Dabas et al., Indian Pediatrics 2020;57:159–164.
---

# CAH Infant Hydrocortisone Dosing Tool

**Source:** Dabas A, et al. Management of Infants with Congenital Adrenal Hyperplasia. *Indian Pediatrics* 2020;57:159–164. (Delhi Pediatric Endocrinology Newborn Screening Group consensus.)

Scope: classical CAH (21-hydroxylase deficiency — SW or SV) from newborn period through early childhood. Not for non-classical CAH, post-pubertal, or adult patients.

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## STEP 1 — Confirm the indication

Use this dosing for:

- Newborn / infant / child with **classical CAH** (salt-wasting OR simple-virilizing).
- Diagnosis confirmed on 17-OHP ± genetics; gender assignment counselling done where relevant.

Do **NOT** use this skill for:

- Non-classical CAH (different dosing, often no GC needed).
- Post-pubertal or adult patients (longer-acting agents become appropriate).
- Adrenal crisis management — use [[cah-adrenal-crisis-protocol]].

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## STEP 2 — Choose the agent (and what to avoid)

| Agent | Use in infants/young children? |
|---|---|
| **Hydrocortisone (oral tablet)** | **First-line.** Short half-life mimics physiological cortisol rhythm. |
| Prednisolone | **Avoid** in young children — overdosing risk, poor 17-OHP suppression, shorter adult height. Acceptable post-puberty. |
| Dexamethasone | **Avoid** in young children — too potent, growth suppression. Acceptable in adults. |
| Modified / extended-release hydrocortisone | **Not advisable** in paediatrics. |
| Cortisone acetate | Not recommended (variable conversion). |

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## STEP 3 — Calculate the daily dose

**Physiological replacement dose: 10–15 mg/m²/day of oral hydrocortisone.**

- Endogenous cortisol production rate ≈ 5.7–7.4 mg/m²/day; the 10–15 mg/m²/day target accounts for first-pass metabolism and bioavailability (~94%).
- Stay within this range. Higher chronic doses → Cushingoid features, growth failure. Lower doses → virilization, accelerated bone age.

**Body surface area (BSA) — Mosteller formula:**

> BSA (m²) = √[ (Height in cm × Weight in kg) / 3600 ]

**Worked example:**
A 6-month-old, weight 7 kg, length 65 cm:
- BSA = √(65 × 7 / 3600) = √0.126 = **0.355 m²**
- Daily dose = 0.355 × 12 mg/m² (mid-range) ≈ **4.3 mg/day**

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## STEP 4 — Split into a thrice-daily schedule

- **Three divided doses per day.** Twice-daily achieves normal serum cortisol in only ~15% of patients vs ~60% with TDS.
- **Morning dose: as early as possible** (matches circadian rhythm).
- Do **NOT** delay the evening dose till bedtime — it does not improve morning 17-OHP suppression.

**Suggested split (for a TDD of ~4.5 mg):**

| Time | Dose |
|---|---|
| Early morning (on waking) | ~1.5 mg (largest or equal share) |
| Mid-day / lunch | ~1.5 mg |
| Early evening | ~1.5 mg |

Some clinicians give a slightly larger morning dose (e.g. 40 / 30 / 30 split); evenly divided is also acceptable.

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## STEP 5 — Prepare and administer correctly

- Use **tablet form**. Crush the tablet and mix with milk or liquid as a **fresh preparation immediately before each dose**.
- Do **NOT** pre-dissolve or pre-suspend hydrocortisone in liquid for later use — drug delivery becomes uneven.
- Oral hydrocortisone has ~94% bioavailability; no need for an IV route in stable outpatients.

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## STEP 6 — Build in stress-dose rules and a disease card

Every CAH infant/child must have:

1. **Sick-day rule prescription** (see [[cah-adrenal-crisis-protocol]] for details):
   - Minor illness (URI, mild fever, mild diarrhoea): **double** oral hydrocortisone.
   - Moderate–severe illness (vomiting, fever > 38.5 °C, lethargy, dehydration, surgery, trauma): **3–5×** oral or switch to IV.
2. **Disease/identification card** to carry at all times (school, travel, picnic):
   - Name, DOB, gender, parent contact, diagnosis "Congenital Adrenal Hyperplasia", emergency steroid instructions, treating doctor.

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## STEP 7 — Plan monitoring at every visit

Clinical (every visit): weight, length/height, BP, genital exam, signs of virilization, skin pigmentation, Cushingoid features.

Biochemical:
- First 3 months: monthly serum electrolytes; baseline 17-OHP recorded.
- 3–12 months: 3-monthly electrolytes + 17-OHP (sample **before** the morning HC dose).
- 12–30 months: 4-monthly electrolytes + 17-OHP; bone age annually after 24 months.
- Optional adjuncts: androstenedione, total testosterone, ACTH, plasma renin activity, aldosterone:renin ratio.

**Targets:**
- 17-OHP: 5–10 ng/mL (do NOT push to age-appropriate normal — implies over-treatment).
- Total testosterone (>6 months, pre-puberty): < 20 ng/dL.
- Normal growth velocity, normal BP, no progressive virilization, no Cushingoid features.

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## STEP 8 — Adjust the dose

| Pattern | Likely problem | Action |
|---|---|---|
| Growth spurt + accelerated bone age + virilization signs | **Under-treatment** | ↑ HC dose (stay ≤ 15 mg/m²/day; rule out missed doses, poor preparation) |
| Weight gain, Cushingoid features, poor growth velocity, hypertension | **Over-treatment** | ↓ HC dose toward 10 mg/m²/day |
| Persistently high 17-OHP but good growth + no virilization | Acceptable — do NOT chase normal 17-OHP | No change |

Adjust by ~10–20% at a time and re-check in 4–6 weeks.

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## Quick reference card

- **Drug:** Oral hydrocortisone tablet (crushed, fresh in milk).
- **Dose:** 10–15 mg/m²/day.
- **Schedule:** 3 divided doses; morning as early as possible.
- **Avoid in young children:** prednisolone, dexamethasone, modified-release HC.
- **Add:** fludrocortisone (all classical CAH) + salt 1–3 g/day (SW first year).
- **Always:** sick-day plan + disease card.
- **Monitor:** 17-OHP target 5–10 ng/mL, growth velocity, bone age, BP, electrolytes.