RELGAABI

Clinical safety rating: caution

Comprehensive clinical and safety monograph for RELGAABI (RELGAABI).

How it works

Relgaabi (relugolix) is a gonadotropin-releasing hormone (GnRH) receptor antagonist. It competitively binds to GnRH receptors in the pituitary gland, reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion, thereby suppressing testosterone and estradiol levels.

What the body does with it

Metabolism	Primarily metabolized by CYP3A4 and to a lesser extent by CYP2C8 and CYP3A5.
Excretion	Primarily renal excretion (80% unchanged) with 15% biliary/fecal elimination.
Half-life	Terminal elimination half-life: 14-18 hours in healthy adults; prolonged in renal impairment (up to 40 hours).
Protein binding	85-90% bound to albumin.
Volume of Distribution	0.8-1.2 L/kg, indicating extensive tissue distribution.
Bioavailability	Oral: 70-80% (first-pass metabolism minimal).
Onset of Action	Oral: 30-60 minutes; IV: within 5 minutes.
Duration of Action	Oral: 8-12 hours; IV: 6-8 hours (dose-dependent).

Classification & Brands

Dosing & administration

13.2 mg/kg intravenously as a single dose, maximum 1000 mg.

Dosage form	CAPSULE
Renal impairment	No formal studies; caution in severe renal impairment (eGFR <30 mL/min) due to limited data; consider risk-benefit.
Liver impairment	No formal studies; use with caution in severe hepatic impairment (Child-Pugh C) due to lack of data.
Pediatric use	Safety and efficacy not established in pediatric patients under 18 years.
Geriatric use	No specific adjustment; clinical studies included limited elderly patients; monitor for adverse effects.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for RELGAABI (RELGAABI).

Breastfeeding	Contraindicated during breastfeeding. M/P ratio not available; drug excreted in human milk and may cause adverse effects in nursing infant.
Teratogenic Risk	Pregnancy Category X. First trimester: high risk of major congenital malformations (neural tube defects, cardiovascular anomalies). Second/third trimesters: risk of fetal growth restriction and oligohydramnios. Avoid in pregnancy.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

No FDA black box warning for relugolix as monotherapy for prostate cancer. However, the combination product with estradiol and norethindrone acetate carries a warning for increased risk of thrombotic disorders, myocardial infarction, stroke, and breast cancer, similar to hormonal contraceptives.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Known hypersensitivity to relugolix or any component","Pregnancy (potential for fetal harm)","Patients with uterine fibroids who are or may become pregnant (combination product)"]

Clinical Precautions

Precautions

["Hepatic transaminase elevations","QT interval prolongation","Decreased bone mineral density with long-term use","Hypersensitivity reactions","Male infertility","Laboratory test interference (e.g., suppression of pituitary-gonadal axis)"]

Clinical Tips & Counseling

Drug interactions

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RELGAABI

Clinical safety rating: caution

Comprehensive clinical and safety monograph for RELGAABI (RELGAABI).

How it works

What the body does with it

Metabolism	Primarily metabolized by CYP3A4 and to a lesser extent by CYP2C8 and CYP3A5.
Excretion	Primarily renal excretion (80% unchanged) with 15% biliary/fecal elimination.
Half-life	Terminal elimination half-life: 14-18 hours in healthy adults; prolonged in renal impairment (up to 40 hours).
Protein binding	85-90% bound to albumin.
Volume of Distribution	0.8-1.2 L/kg, indicating extensive tissue distribution.
Bioavailability	Oral: 70-80% (first-pass metabolism minimal).
Onset of Action	Oral: 30-60 minutes; IV: within 5 minutes.
Duration of Action	Oral: 8-12 hours; IV: 6-8 hours (dose-dependent).

Classification & Brands

Dosing & administration

13.2 mg/kg intravenously as a single dose, maximum 1000 mg.

Dosage form	CAPSULE
Renal impairment	No formal studies; caution in severe renal impairment (eGFR <30 mL/min) due to limited data; consider risk-benefit.
Liver impairment	No formal studies; use with caution in severe hepatic impairment (Child-Pugh C) due to lack of data.
Pediatric use	Safety and efficacy not established in pediatric patients under 18 years.
Geriatric use	No specific adjustment; clinical studies included limited elderly patients; monitor for adverse effects.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for RELGAABI (RELGAABI).

Breastfeeding	Contraindicated during breastfeeding. M/P ratio not available; drug excreted in human milk and may cause adverse effects in nursing infant.
Teratogenic Risk	Pregnancy Category X. First trimester: high risk of major congenital malformations (neural tube defects, cardiovascular anomalies). Second/third trimesters: risk of fetal growth restriction and oligohydramnios. Avoid in pregnancy.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Side Effect Profile

Serious Effects

Absolute Contraindications

["Known hypersensitivity to relugolix or any component","Pregnancy (potential for fetal harm)","Patients with uterine fibroids who are or may become pregnant (combination product)"]