11β-hydroxylase inhibitor

Osilodrostat

Brand names: Isturisa

Osilodrostat is an oral cortisol synthesis inhibitor used to treat endogenous Cushing's syndrome.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits 11-beta-hydroxylase, the enzyme catalysing the final step of cortisol biosynthesis, thereby reducing cortisol production.

Prescribing in practice

Hypocortisolism can occur as cortisol falls, so patients must be monitored and educated to recognise and manage adrenal insufficiency.
It can prolong the QT interval, so an ECG and electrolytes should be checked before and during treatment.
Accumulation of adrenal hormone precursors may cause hypokalaemia, oedema, hypertension and increased androgenic effects such as hirsutism.

Monitoring

Monitor cortisol levels, potassium, blood pressure and ECG (QT interval), titrating the dose to achieve cortisol control without insufficiency.

Counselling the patient

Seek urgent help for symptoms of low cortisol such as severe tiredness, nausea, dizziness or low blood pressure.
Attend all blood tests and heart tracings so the dose can be adjusted safely.
Report palpitations or fainting promptly.

Evidence & guidelines

Osilodrostat is licensed for Cushing's syndrome based on trials demonstrating normalisation of urinary free cortisol.

Reference: NICE TA928 (Osilodrostat); SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways