Synthetic ACTH (short Synacthen test) Pregnancy: Limited data in pregnant women; animal studies insufficient. Use during pregnancy only if the expected benefit outweighs the potential risk to the foetus. It is not known whether tetracosactide enters breast milk — caution if administered to a breastfeeding woman.

Tetracosactide

Brand names: Synacthen, Synacthen Depot

Tetracosactide is a synthetic adrenocorticotrophic hormone (ACTH) analogue used mainly as a diagnostic agent to test adrenocortical function (the short Synacthen test). A depot form has also been used therapeutically in certain inflammatory conditions.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 250 micrograms (1 ml)

Route: Single intramuscular or intravenous injection

Frequency: Single dose — diagnostic use only; this preparation is not to be used for repeated therapeutic administration

30-minute Synacthen (short synacthen) diagnostic test: measure plasma cortisol immediately before and exactly 30 minutes after a 250 microgram intramuscular or intravenous injection. Adrenocortical function is regarded as normal if the post-injection plasma cortisol rises by 200 nmol/litre (70 micrograms/litre), i.e. if the 30-minute value is >500 nmol/litre (180 micrograms/litre). Store all plasma samples in a refrigerator until cortisol estimation. Where the 30-minute test is inconclusive, or to determine adrenocortical functional reserve, a 5-hour test can be performed with Synacthen Depot (separate SPC); a 3-day Synacthen Depot test may be used to differentiate primary from secondary adrenocortical insufficiency. Elderly: no evidence that dosage should differ. Children: the SPC suggests an intravenous dose of 250 micrograms/1.73 m2 body surface area (body-surface-area based, NOT per kg) — thus for children aged 5 to 7 years approximately half the adult dose will be adequate; consult standard body surface area tables for other ages, and verify paediatric dosing against a children's formulary. Administer only under the supervision of appropriate senior hospital medical staff; hypersensitivity reactions tend to occur within 30 minutes, so keep the patient under observation for that period with preparation in advance to treat anaphylaxis (adrenaline and steroids). Results may be misleading where cortisol-binding globulin is altered (oral contraceptives, post-operative patients, critical illness, severe liver disease, nephrotic syndrome). Source: eMC SPC for Synacthen Ampoules 250 micrograms.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to tetracosactide and/or ACTH or to any of the excipients
Allergic disorders (e.g. asthma)
Acute psychosis
Infectious diseases
Peptic ulcer
Refractory heart failure
Cushing's syndrome
Treatment of primary adrenocortical insufficiency and adrenocongenital syndrome

Side effects

Hypersensitivity reactions (frequency not known) — skin reactions at the injection site, dizziness, nausea, vomiting, urticaria, pruritus, flushing, malaise, dyspnoea, angioneurotic and Quincke's oedema; anaphylactic shock, particularly in patients susceptible to allergies (especially asthma)
Adrenal haemorrhage
Glucocorticoid/mineralocorticoid effects (unlikely with short-term diagnostic use): hypokalaemia, sodium and fluid retention, hyperglycaemia
Psychiatric disturbance; convulsions, vertigo, headache; raised intraocular pressure, glaucoma, cataract
Hypertension, thromboembolism, congestive cardiac failure; pancreatitis, peptic ulcer with possible perforation and haemorrhage

Interactions

Altered cortisol-binding globulin states (oral contraceptives, post-operative patients, critical illness, severe liver disease, nephrotic syndrome) — post-administration total plasma cortisol may be misleading; consider alternative parameters (SPC §4.4)
Live vaccines — Synacthen Ampoules should not be used when use of a live vaccine is contemplated, or in the presence of reduced immune response, unless disease-specific therapy is given (SPC §4.4)
Diuretics — corticotropin may accentuate the electrolyte loss associated with diuretic therapy (US cosyntropin labelling)
Dosage adjustments may be necessary in patients being treated for diabetes or hypertension (SPC §4.4)

Clinical monograph

How it works

It is a synthetic polypeptide corresponding to the first part of the ACTH molecule that stimulates the adrenal cortex, via melanocortin receptors, to synthesise and release corticosteroids, principally cortisol.

Prescribing in practice

It is contraindicated in patients with a history of allergic disorders or previous hypersensitivity to ACTH preparations, as it can cause serious anaphylactic reactions, and facilities to treat anaphylaxis should be available.
A normal cortisol response to the test does not exclude all forms of adrenal insufficiency, and results must be interpreted in clinical context.
When used therapeutically it produces the same adverse effects as systemic corticosteroids and does not allow the precise control of an oral steroid dose.

Monitoring

For the diagnostic test, monitor plasma cortisol before and after administration and observe the patient for any hypersensitivity reaction.

Counselling the patient

This is usually given as a one-off injection as part of a hormone test, with a blood sample taken before and after.
Tell the clinician beforehand if you have any history of allergy or asthma.
Report any rash, wheeze, swelling, or faintness after the injection.

Evidence & guidelines

Its use in assessing adrenocortical reserve is well established and forms the basis of the standard short synacthen test.

Reference: UK Endocrine Society; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways