What Are Corticosteroids?

Corticosteroids are synthetic versions of hormones naturally produced by the adrenal glands. They are among the most powerful anti-inflammatory and immunosuppressant agents available, used in conditions ranging from asthma to autoimmune disease to severe allergic reactions.

Mechanism

Bind to glucocorticoid receptors inside cells, altering gene expression to suppress inflammatory cytokine production, reduce immune cell activity, and stabilize cell membranes.

Common Uses

Asthma, COPD exacerbations, allergic reactions, rheumatoid arthritis, lupus, inflammatory bowel disease, organ transplant rejection prevention, adrenal insufficiency.

Key Risks

Immune suppression (infection risk), blood sugar elevation, osteoporosis with long-term use, adrenal suppression, weight gain, mood changes, cataracts, HPA axis suppression.

Examples

Prednisone (oral, systemic), budesonide (inhaled/GI), fluticasone (inhaled/nasal), dexamethasone, hydrocortisone, methylprednisolone.

How Corticosteroids Work

Corticosteroids are lipid-soluble molecules that pass easily through cell membranes. Inside the cell, they bind to the glucocorticoid receptor (GR) — a protein that sits in the cytoplasm. The steroid-receptor complex then moves into the nucleus, where it directly regulates the transcription of hundreds of genes.

The net effect is a broad suppression of inflammation: reduced production of pro-inflammatory cytokines (interleukin-1, interleukin-6, TNF-alpha), decreased activity of immune cells (lymphocytes, macrophages, eosinophils), and reduced vascular permeability that limits swelling and redness. Corticosteroids also increase the production of anti-inflammatory proteins such as lipocortin, which inhibits phospholipase A2 — the enzyme that initiates arachidonic acid pathway inflammation (the same pathway NSAIDs block downstream).

Route of administration dramatically influences systemic exposure and side-effect burden. Inhaled corticosteroids (budesonide, fluticasone) are designed to act locally in the airways with high first-pass metabolism in the liver, minimizing systemic effects. Oral systemic agents (prednisone) and IV forms produce robust systemic effects appropriate for acute severe inflammation or autoimmune conditions — but this potency comes with a substantial side-effect profile, particularly with long-term use.

Drugs in This Class

Prednisone

Deltasone, Rayos — oral systemic

View drug →

Budesonide

Pulmicort, Entocort EC, Symbicort

View drug →

Fluticasone

Flovent, Flonase, Advair

View drug →

Common Side Effects Across the Class

Weight gain and increased appetite

Elevated blood sugar (glucose)

Mood changes, insomnia, anxiety

Fluid retention and swelling

Increased infection susceptibility

Bone loss (osteoporosis) with long-term use

Skin thinning and easy bruising

Oral thrush (inhaled steroids)

Important Interactions & Warnings

NSAIDs — Combining corticosteroids with NSAIDs dramatically increases the risk of GI ulceration and bleeding. A proton pump inhibitor should be co-prescribed if this combination is necessary.
Diabetes medications — Corticosteroids raise blood glucose levels, sometimes significantly. Patients with diabetes may require upward adjustments to their antidiabetic regimen during steroid courses. Blood glucose should be monitored.
Live vaccines — Systemic corticosteroids suppress the immune system. Live attenuated vaccines (MMR, varicella, yellow fever) are generally contraindicated during systemic steroid use. Consult your provider about vaccine timing.
HPA axis suppression and adrenal insufficiency — Prolonged systemic corticosteroid use suppresses the hypothalamic-pituitary-adrenal (HPA) axis. Abrupt discontinuation after long-term use can cause adrenal insufficiency — a potentially life-threatening deficiency in the body's own cortisol production. Always taper systemic steroids gradually under medical supervision.
Antifungals (ketoconazole, itraconazole) — Strong CYP3A4 inhibitors can increase corticosteroid blood levels, enhancing effects and side effects.
Bone protection — Patients on long-term systemic corticosteroids should receive calcium, vitamin D supplementation, and bisphosphonate therapy (e.g., alendronate) if indicated, to prevent steroid-induced osteoporosis.

Frequently Asked Questions

Are inhaled corticosteroids the same as systemic steroids?

No — they are very different in terms of systemic exposure and side effects. Inhaled corticosteroids (ICS) like fluticasone and budesonide are delivered directly to the airways in very small amounts and are designed to be absorbed locally with minimal systemic absorption. They are safe for long-term use in asthma. Systemic corticosteroids (oral prednisone, IV methylprednisolone) distribute throughout the body and carry significant side effects with prolonged use. ICS do not cause the bone loss, weight gain, or immunosuppression associated with systemic steroids at typical therapeutic doses.

Why must prednisone be tapered and not stopped abruptly?

When the body is exposed to exogenous (external) corticosteroids, the adrenal glands reduce their own cortisol production — a process called HPA axis suppression. If the drug is stopped suddenly, the adrenals cannot immediately resume normal output, and the body enters a state of adrenal insufficiency. This can cause weakness, hypotension, nausea, and in severe cases, adrenal crisis. Gradual tapering gives the adrenal glands time to recover function. The longer and higher the steroid exposure, the more gradual the taper needs to be.

Do corticosteroids cause weight gain?

Yes — especially with systemic use lasting more than a few weeks. Corticosteroids promote fat redistribution (toward the face, neck, and abdomen), increase appetite, and cause fluid retention. The characteristic "moon face" and "buffalo hump" of Cushing's syndrome reflect the effects of chronically elevated cortisol, which can be drug-induced. Inhaled or topical steroids at standard doses are far less likely to cause significant weight gain.

Can I use a steroid nasal spray every day?

Yes. Intranasal corticosteroids like fluticasone propionate (Flonase) and budesonide (Rhinocort) are designed for daily use and are considered safe for long-term management of allergic rhinitis. They act locally in the nasal passages with minimal systemic absorption. They are actually first-line for allergic rhinitis, more effective than oral antihistamines for nasal congestion. Rinse the throat and mouth after use to minimize any local irritation.