PRELAY

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PRELAY (PRELAY).

How it works

Selective estrogen receptor modulator (SERM) that antagonizes estrogen's effects in breast tissue and agonizes estrogen's effects in bone, endometrium, and lipid metabolism.

What the body does with it

Metabolism	Hepatic glucuronidation (UGT1A1, UGT1A8, UGT1A10); minimal cytochrome P450 involvement.
Excretion	Primarily renal excretion as unchanged drug (60-70%) and metabolites (10-20%); fecal excretion accounts for <10%.
Half-life	Terminal elimination half-life is 2-4 hours; in severe renal impairment (CrCl <30 mL/min), half-life increases to 6-12 hours, requiring dose adjustment.
Protein binding	Approximately 95% bound to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	0.2-0.4 L/kg, indicating limited extravascular distribution, primarily confined to plasma and interstitial fluid.
Bioavailability	Oral bioavailability is 75-90% due to extensive first-pass metabolism; rectal and intramuscular routes have bioavailability of 60-80% and 85-95%, respectively.
Onset of Action	Oral: 30-60 minutes; Intravenous: within 5 minutes.
Duration of Action	Oral: 4-6 hours; Intravenous: 2-4 hours. Duration may be prolonged in hepatic impairment due to reduced metabolism.

Classification & Brands

Dosing & administration

0.2 mg subcutaneously once daily, titrated to 0.4 mg subcutaneously once daily after 2 weeks if tolerated and no excessive hypotension. Maximum dose: 0.4 mg subcutaneously once daily.

Dosage form	TABLET
Renal impairment	No dose adjustment required for any degree of renal impairment including end-stage renal disease.
Liver impairment	No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Contraindicated in severe hepatic impairment (Child-Pugh C).
Pediatric use	Not approved for use in pediatric patients (safety and efficacy not established).
Geriatric use	No specific dose adjustment required; consider starting at 0.2 mg subcutaneously once daily and titrate slowly due to increased sensitivity to hypotension in elderly patients.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for PRELAY (PRELAY).

Breastfeeding	Contraindicated during breastfeeding. M/P ratio not determined; drug is excreted in human milk and may cause serious adverse reactions in nursing infants.
Teratogenic Risk	Pregnancy Category X. First trimester: high risk of major congenital malformations including cardiovascular and neural tube defects. Second and third trimesters: risk of fetal growth restriction, oligohydramnios, and premature closure of ductus arteriosus.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Increased risk of venous thromboembolic events (deep vein thrombosis and pulmonary embolism) and death due to stroke. Use is contraindicated in women with a history of or active venous thromboembolic events, including deep vein thrombosis, pulmonary embolism, and retinal vein thrombosis. Use is also contraindicated in women with a history of or active arterial thromboembolic events, including stroke and transient ischemic attack.

Side Effect Profile

Serious Effects

Absolute Contraindications

Active or history of venous thromboembolism (deep vein thrombosis, pulmonary embolism, retinal vein thrombosis); active or history of arterial thromboembolism (stroke, transient ischemic attack); women of childbearing potential; pregnancy; lactation.

Clinical Precautions

Precautions

Increased risk of venous thromboembolism and stroke; discontinue if immobilization occurs; monitor for signs of stroke or venous thromboembolism; use with caution in patients with hepatic impairment; may cause hypertriglyceridemia; avoid use with systemic estrogens or hormone replacement therapy.

Clinical Tips & Counseling

Drug interactions

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PRELAY

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PRELAY (PRELAY).

How it works

Selective estrogen receptor modulator (SERM) that antagonizes estrogen's effects in breast tissue and agonizes estrogen's effects in bone, endometrium, and lipid metabolism.

What the body does with it

Metabolism	Hepatic glucuronidation (UGT1A1, UGT1A8, UGT1A10); minimal cytochrome P450 involvement.
Excretion	Primarily renal excretion as unchanged drug (60-70%) and metabolites (10-20%); fecal excretion accounts for <10%.
Half-life	Terminal elimination half-life is 2-4 hours; in severe renal impairment (CrCl <30 mL/min), half-life increases to 6-12 hours, requiring dose adjustment.
Protein binding	Approximately 95% bound to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	0.2-0.4 L/kg, indicating limited extravascular distribution, primarily confined to plasma and interstitial fluid.
Bioavailability	Oral bioavailability is 75-90% due to extensive first-pass metabolism; rectal and intramuscular routes have bioavailability of 60-80% and 85-95%, respectively.
Onset of Action	Oral: 30-60 minutes; Intravenous: within 5 minutes.
Duration of Action	Oral: 4-6 hours; Intravenous: 2-4 hours. Duration may be prolonged in hepatic impairment due to reduced metabolism.

Classification & Brands

Dosing & administration

0.2 mg subcutaneously once daily, titrated to 0.4 mg subcutaneously once daily after 2 weeks if tolerated and no excessive hypotension. Maximum dose: 0.4 mg subcutaneously once daily.

Dosage form	TABLET
Renal impairment	No dose adjustment required for any degree of renal impairment including end-stage renal disease.
Liver impairment	No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Contraindicated in severe hepatic impairment (Child-Pugh C).
Pediatric use	Not approved for use in pediatric patients (safety and efficacy not established).
Geriatric use	No specific dose adjustment required; consider starting at 0.2 mg subcutaneously once daily and titrate slowly due to increased sensitivity to hypotension in elderly patients.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for PRELAY (PRELAY).

Breastfeeding	Contraindicated during breastfeeding. M/P ratio not determined; drug is excreted in human milk and may cause serious adverse reactions in nursing infants.
Teratogenic Risk	Pregnancy Category X. First trimester: high risk of major congenital malformations including cardiovascular and neural tube defects. Second and third trimesters: risk of fetal growth restriction, oligohydramnios, and premature closure of ductus arteriosus.
Fetal Monitoring