Hydrocortisone (Cortef): Uses, Dosing, Side Effects, and How It Compares to Prednisone, Dexamethasone, and Fludrocortisone

What Is Hydrocortisone (Cortef) and What Is It Used For?

Hydrocortisone is the synthetic form of cortisol, the primary glucocorticoid secreted by the zona fasciculata of the adrenal cortex. Unlike prednisone or dexamethasone, which are purely pharmacologic anti-inflammatory agents, hydrocortisone is used at physiologic doses to replace hormone the body cannot produce on its own. The FDA has approved Cortef for adrenal insufficiency (both primary and secondary), congenital adrenal hyperplasia (CAH), and a broad list of inflammatory, allergic, rheumatic, and dermatologic conditions.

Primary adrenal insufficiency (Addison's disease) affects roughly 100, 140 people per 100 to 000 in Western populations, according to registry data published in the European Journal of Endocrinology [1]. Secondary adrenal insufficiency, caused most often by prolonged exogenous corticosteroid use suppressing the hypothalamic-pituitary-adrenal (HPA) axis, is considerably more common. The 2016 Endocrine Society Clinical Practice Guideline on adrenal insufficiency recommends hydrocortisone as the first-choice glucocorticoid for replacement therapy in adults, citing its pharmacokinetic similarity to endogenous cortisol [2].

A healthy adrenal gland secretes approximately 5 to 10 mg of cortisol per square meter of body surface area daily, which translates to roughly 15 to 25 mg of oral hydrocortisone in most adults when accounting for first-pass hepatic metabolism. Cortef tablets come in 5 mg, 10 mg, and 20 mg strengths, making it straightforward to titrate replacement to individual need.

Beyond adrenal insufficiency, short courses of higher-dose hydrocortisone (100 to 500 mg IV, as Solu-Cortef) are used in hospitals for anaphylaxis, severe asthma exacerbations, thyroid storm, and perioperative stress coverage in adrenal-insufficient patients.

How Hydrocortisone Compares to Prednisone, Prednisolone, and Dexamethasone

Choosing among corticosteroids is not arbitrary. Each agent differs in potency, duration of action, mineralocorticoid activity, and HPA-axis suppression potential.

The standard corticosteroid equivalency table used by most endocrinologists:

| Drug | Anti-inflammatory potency (relative) | Mineralocorticoid potency (relative) | Biologic half-life | |---|---|---|---| | Hydrocortisone | 1 | 1 | 8, 12 h | | Prednisone | 4 | 0.8 | 18, 36 h | | Prednisolone | 4 | 0.8 | 18, 36 h | | Dexamethasone | 25, 30 | ~0 | 36, 54 h | | Fludrocortisone | 10 (glucocorticoid) | 125, 150 | 18, 36 h |

Prednisone is a prodrug converted in the liver to prednisolone, the active form. Prednisone carries four times the anti-inflammatory potency of hydrocortisone at equal milligram doses and suppresses the HPA axis more deeply for the same anti-inflammatory effect [3]. This makes prednisone a poor choice for physiologic replacement but an efficient choice for conditions like rheumatoid arthritis, inflammatory bowel disease, or acute exacerbations of asthma, where the goal is pharmacologic suppression rather than replacement.

Prednisolone is the active metabolite of prednisone, used directly in patients with significant hepatic impairment who may not convert prednisone reliably. It is the preferred oral glucocorticoid for children in the United Kingdom and Australia. Bioavailability is more predictable than prednisone but clinical anti-inflammatory equivalency is essentially the same [4].

Dexamethasone has no clinically meaningful mineralocorticoid activity and a biologic half-life of 36 to 54 hours, making it the most potent and longest-acting agent in routine clinical use. The RECOVERY trial (N=6,425) demonstrated that dexamethasone 6 mg daily for up to 10 days reduced 28-day mortality in hospitalized COVID-19 patients requiring respiratory support, with a rate ratio of 0.83 (95% CI 0.75, 0.93, P<0.001) [5]. Dexamethasone is also the agent of choice for cerebral edema, bacterial meningitis adjunctive therapy, and fetal lung maturation in preterm labor because it crosses the placenta efficiently and does not bind placental 11-beta-hydroxysteroid dehydrogenase type 2.

Fludrocortisone (Florinef) occupies a separate niche. It has roughly 10 times the glucocorticoid potency of hydrocortisone but 125 to 150 times the mineralocorticoid potency, making it the standard agent for mineralocorticoid replacement in primary adrenal insufficiency and for managing salt-wasting forms of CAH. The Endocrine Society guideline recommends 0.05 to 0.2 mg of fludrocortisone once daily as adjunctive therapy alongside hydrocortisone in patients with primary adrenal insufficiency [2]. Fludrocortisone is not appropriate as a standalone glucocorticoid replacement because its glucocorticoid effect at mineralocorticoid-effective doses would produce significant HPA suppression and cushingoid features.

Hydrocortisone Dosing for Adrenal Insufficiency: Physiologic Replacement

Standard physiologic replacement targets the body's normal daily cortisol production rate and mimics its circadian rhythm. Cortisol peaks within 30 to 60 minutes of waking and falls to its nadir around midnight.

The 2016 Endocrine Society guideline recommends 15 to 25 mg of hydrocortisone daily, divided into two or three doses [2]. A common split is 10 mg on waking, 5 mg at noon, and 5 mg in the early afternoon (no later than 4:00 PM to avoid nocturnal sleep disruption). The largest dose is given on waking to replicate the cortisol awakening response. Patients who are overreplaced chronically face the same metabolic consequences as those on long-term prednisone: weight gain, dysglycemia, hypertension, osteoporosis, and adrenal axis suppression that prevents recovery.

A prospective cohort study published in the Journal of Clinical Endocrinology and Metabolism (N=91) found that patients on mean daily hydrocortisone doses above 20 mg had significantly lower bone mineral density at the lumbar spine than those on doses at or below 20 mg (P<0.05) [6]. This underscores the importance of using the lowest effective replacement dose.

Modified-release hydrocortisone (Plenadren, not yet widely available in the United States but used in Europe) delivers a once-daily dose with a delayed-release tail designed to better approximate the diurnal cortisol curve. A randomized crossover trial (N=64) showed improved metabolic profiles and reduced weight versus conventional immediate-release hydrocortisone at 12 months [7].

Stress Dosing: When and How to Double or Triple the Dose

Patients with adrenal insufficiency cannot mount the normal cortisol stress response that healthy individuals produce automatically during illness, surgery, or trauma. Without additional hydrocortisone, they risk adrenal crisis, which carries a mortality rate of approximately 6% per crisis episode based on German registry data (N=883 patients, 1,675 crisis events) [8].

The general stress-dosing framework:

• Minor physiologic stress (common cold, mild fever): double the daily dose for the duration of the illness.
• Moderate stress (vomiting, high fever above 38.5 degrees C, moderate dental procedure, colonoscopy): triple the daily dose; if oral intake is compromised, switch to parenteral hydrocortisone.
• Major stress (surgery under general anesthesia, severe infection, significant trauma): 50 to 100 mg IV hydrocortisone at the time of the procedure, followed by 200 mg per 24 hours by continuous infusion or divided bolus until the patient is stable and tolerating oral intake.

Patients should carry a medical alert bracelet and an emergency injection kit containing hydrocortisone 100 mg (Solu-Cortef Act-O-Vial) for self-administration or administration by a bystander if they lose consciousness. The Society for Endocrinology and the Endocrine Society both publish patient sick-day rules reinforcing this protocol [2].

Side Effects of Hydrocortisone at Replacement Versus Pharmacologic Doses

Side effects depend heavily on whether hydrocortisone is used at physiologic replacement doses or at higher pharmacologic doses for inflammatory conditions.

At physiologic replacement doses (15 to 25 mg/day): Most patients tolerate this well. The main risks are overreplacement (cushingoid features, weight gain, hypertension, dysglycemia, osteoporosis) and underreplacement (fatigue, hypotension, hyponatremia, hypoglycemia). Insomnia is a common complaint when afternoon doses are taken too late in the day.

At pharmacologic doses (above 30 to 40 mg/day for more than 3 weeks):

• HPA axis suppression and subsequent adrenal insufficiency on tapering
• Weight gain and redistribution of fat to the trunk, face, and posterior neck
• New-onset or worsened diabetes mellitus (steroid-induced hyperglycemia affects up to 32% of hospitalized patients receiving moderate-to-high-dose corticosteroids, per a systematic review in Diabetes Care) [9]
• Osteoporosis: the American College of Rheumatology recommends calcium (1,000, 1 to 200 mg/day), vitamin D (600 to 800 IU/day), and bisphosphonate therapy for any patient expected to take the equivalent of 7.5 mg or more of prednisone for 3 or more months [10]
• Gastrointestinal: peptic ulcer, particularly when combined with NSAIDs
• Neuropsychiatric: mood lability, euphoria, insomnia, and at higher doses, steroid psychosis
• Immune suppression: increased susceptibility to bacterial, viral, fungal, and opportunistic infections
• Ocular: posterior subcapsular cataracts and elevated intraocular pressure with prolonged use
• Hypokalemia and sodium retention at higher doses due to residual mineralocorticoid activity

Prednisone at equivalent doses carries a broadly similar side-effect profile, but because prednisone has greater per-milligram potency, a lower absolute daily milligram dose is needed to produce the same anti-inflammatory effect, which may reduce some mineralocorticoid-mediated effects (fluid retention, hypertension) compared to equivalent hydrocortisone.

Tapering Hydrocortisone and Avoiding Adrenal Crisis

Any patient who has received more than the equivalent of 20 mg/day of hydrocortisone (or 5 mg/day of prednisone) for more than 3 weeks should be tapered, not stopped abruptly. Abrupt discontinuation risks adrenal insufficiency because prolonged exogenous corticosteroid suppresses hypothalamic CRH secretion and pituitary ACTH release, and the adrenal cortex then atrophies from disuse.

A common tapering schedule for moderate-duration courses:

1. Reduce total daily hydrocortisone by 10 to 20% every 1 to 2 weeks until reaching 20 mg/day.
2. At 20 mg/day, slow the taper to 2.5 to 5 mg decrements every 2 to 4 weeks.
3. At 10 mg/day, check morning (8:00 AM) serum cortisol to assess axis recovery. A level above 18 mcg/dL generally indicates adequate adrenal function, though institutional cut-offs vary.

The pace must be individualized. Patients with longer exposure, higher prior doses, or comorbid autoimmune conditions often need slower tapers. Symptoms of steroid withdrawal (fatigue, myalgia, arthralgia, mood changes, nausea) can mimic an adrenal insufficiency flare and complicate clinical assessment.

Hydrocortisone in Congenital Adrenal Hyperplasia

Hydrocortisone is the preferred glucocorticoid for children with CAH because its shorter biologic half-life reduces the risk of growth suppression compared to dexamethasone or prednisone [2]. CAH most often results from 21-hydroxylase deficiency (accounting for approximately 95% of cases), which blocks cortisol synthesis and causes a compensatory ACTH surge that drives adrenal androgen overproduction.

In pediatric CAH management, hydrocortisone doses of 10 to 15 mg/m2/day in three divided doses suppress excess androgen synthesis while minimizing growth-suppressive effects. A study published in JAMA (N=203 children with classic CAH) found that mean hydrocortisone doses above 17 mg/m2/day were independently associated with reduced adult height standard deviation scores (P<0.05) [11]. Salt-wasting CAH also requires fludrocortisone at 0.05 to 0.2 mg/day alongside hydrocortisone.

Fludrocortisone (Florinef): The Mineralocorticoid Component of Replacement

Fludrocortisone acts primarily on the mineralocorticoid receptor in the distal nephron, increasing sodium reabsorption and potassium excretion. This maintains extracellular fluid volume and blood pressure in patients who lack aldosterone, the adrenal gland's primary mineralocorticoid.

Standard dosing for adults with primary adrenal insufficiency is 0.05 to 0.2 mg once daily by mouth [2]. Monitoring includes blood pressure (target <130/80 mmHg), serum potassium (target within normal range), plasma renin activity (target upper-normal), and clinical assessment for signs of over-replacement (edema, hypertension) or under-replacement (salt craving, postural hypotension, hyperkalemia).

Fludrocortisone is not used in secondary adrenal insufficiency because aldosterone secretion is regulated by the renin-angiotensin system rather than ACTH, and patients with secondary adrenal insufficiency typically retain intact mineralocorticoid function.

The Endocrine Society guideline states directly: "We suggest fludrocortisone (starting dose 50 mcg/day) for patients with primary adrenal insufficiency, with the daily dose adjusted by clinical assessment and biochemical monitoring" [2].

Drug Interactions With Hydrocortisone and Other Corticosteroids

Several drug classes alter corticosteroid exposure or amplify side effects:

• CYP3A4 inducers (rifampicin, phenytoin, carbamazepine, St. John's Wort): accelerate hepatic metabolism of hydrocortisone, prednisolone, and prednisone, potentially precipitating adrenal crisis in replacement-dependent patients. Dose increases of 50 to 100% may be required.
• CYP3A4 inhibitors (ketoconazole, ritonavir, clarithromycin): reduce corticosteroid clearance and increase toxicity risk.
• NSAIDs: additive GI ulceration risk. Proton pump inhibitor prophylaxis is generally recommended for patients on both agents for more than 2 weeks.
• Oral hypoglycemic agents and insulin: corticosteroids antagonize insulin action; dose adjustments are often needed in patients with diabetes.
• Loop diuretics: additive hypokalemia, particularly with high-dose hydrocortisone or fludrocortisone.
• Antihypertensives: corticosteroid-mediated sodium retention may blunt the effect of ACE inhibitors and diuretics.

Patients transitioning between corticosteroids (for example, from prednisone to hydrocortisone when shifting from pharmacologic to replacement therapy) should use the equivalency table above to calculate the starting dose and should be monitored for signs of both over- and under-replacement during the first 4 to 8 weeks.

Monitoring Patients on Long-Term Hydrocortisone or Prednisone

Long-term corticosteroid therapy warrants systematic monitoring to catch complications early. The American College of Rheumatology and the Endocrine Society recommend:

• Bone density (DEXA scan): at baseline for anyone expected to need the equivalent of 7.5 mg prednisone per day for 3 months or more, then annually [10].
• Fasting glucose or HbA1c: at baseline and every 6 to 12 months.
• Blood pressure: at every visit.
• Ophthalmic exam: annually for patients on long-term therapy to screen for cataracts and glaucoma.
• Weight and body composition: at each visit.
• Serum potassium: particularly in patients also receiving fludrocortisone or diuretics.
• Morning serum cortisol (8:00 AM): when tapering toward discontinuation to assess HPA recovery.

For patients with primary adrenal insufficiency on stable hydrocortisone and fludrocortisone replacement, annual visits with an endocrinologist are standard practice. Plasma renin activity is the preferred biochemical marker for adequacy of fludrocortisone dosing.

The Endocrine Society guideline explicitly states: "We recommend against routinely measuring serum or urinary cortisol to assess the adequacy of glucocorticoid replacement in most patients with adrenal insufficiency, because these measurements do not reliably reflect tissue cortisol exposure" [2].

The most reliable guide to adequate glucocorticoid replacement remains clinical assessment: energy levels, blood pressure (both lying and standing), weight, electrolytes, and absence of adrenal crisis episodes.