TOLAK

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TOLAK (TOLAK).

How it works

TOLAK (tazarotene) is a retinoid prodrug that is converted to its active metabolite tazarotenic acid, which binds selectively to retinoic acid receptors (RARs) such as RARβ and RARγ; this modulates gene expression involved in cell proliferation, differentiation, and inflammation.

What the body does with it

Metabolism	Hepatic esterases convert tazarotene to its active metabolite tazarotenic acid; further metabolized via sulfoxidation and glucuronidation; CYP450 enzymes not involved.
Excretion	Tolak (fluorouracil) is primarily eliminated via metabolism; less than 10% is excreted unchanged in urine. Fecal excretion accounts for approximately 10-20% of the administered dose.
Half-life	The terminal elimination half-life of fluorouracil is approximately 10-20 minutes due to rapid catabolism by dihydropyrimidine dehydrogenase. Clinically, this short half-life necessitates continuous infusion for sustained systemic exposure.
Protein binding	Fluorouracil is minimally bound to plasma proteins, with a free fraction greater than 85%. Binding primarily occurs to albumin, but is less than 10% at therapeutic concentrations.
Volume of Distribution	The volume of distribution of fluorouracil is approximately 0.6-0.8 L/kg, indicating distribution into total body water and some tissue binding, though it is not extensively bound to tissues.
Bioavailability	Topical application: Bioavailability is <5% due to low systemic absorption. Oral bioavailability is highly variable (10-50%) and not used clinically due to erratic absorption and metabolism. Intravenous administration yields 100% bioavailability.
Onset of Action	Topical application: Clinical effects (e.g., erythema, erosion) typically appear within 2-4 weeks of twice-daily application. Systemic absorption is minimal (<5%), so onset for systemic effects is not relevant.
Duration of Action	Topical: Duration of effect lasts about 2-4 weeks after treatment discontinuation, with healing often continuing for several more weeks. Systemic duration is not applicable due to rapid clearance.

Classification & Brands

Dosing & administration

Adults: 200 mg orally twice daily.

Dosage form	CREAM
Renal impairment	GFR 30-89 mL/min: no adjustment. GFR 15-29 mL/min: 200 mg once daily. GFR <15 mL/min or dialysis: contraindicated.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: 200 mg once daily. Child-Pugh C: contraindicated.
Pediatric use	Weight <30 kg: 5 mg/kg twice daily; Weight ≥30 kg: 200 mg twice daily.
Geriatric use	No dose adjustment required; monitor renal function closely.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for TOLAK (TOLAK).

Breastfeeding	Excreted in breast milk; M/P ratio unknown. Due to potential for serious adverse reactions in nursing infants, breastfeeding is contraindicated during therapy and for at least 1 month after last dose.
Teratogenic Risk	Contraindicated in pregnancy. Known teratogen; first trimester exposure causes major congenital malformations (e.g., craniofacial defects, CNS abnormalities). Second and third trimester exposure associated with growth retardation and neurodevelopmental impairment.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Contraindicated in pregnancy (Pregnancy Category X) due to risk of fetal harm; women of childbearing potential must use effective contraception and have a negative pregnancy test before therapy.

Side Effect Profile

Serious Effects

Absolute Contraindications

Pregnancy or women planning pregnancy; known hypersensitivity to retinoids or any component of the formulation.

Clinical Precautions

Precautions

Pregnancy category X; avoid excessive sun exposure/use sunscreens; may cause local irritation; caution in skin conditions with impaired barrier; avoid use in eczematous skin.

Clinical Tips & Counseling

Drug interactions

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TOLAK

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TOLAK (TOLAK).

How it works

What the body does with it

Metabolism	Hepatic esterases convert tazarotene to its active metabolite tazarotenic acid; further metabolized via sulfoxidation and glucuronidation; CYP450 enzymes not involved.
Excretion	Tolak (fluorouracil) is primarily eliminated via metabolism; less than 10% is excreted unchanged in urine. Fecal excretion accounts for approximately 10-20% of the administered dose.
Half-life	The terminal elimination half-life of fluorouracil is approximately 10-20 minutes due to rapid catabolism by dihydropyrimidine dehydrogenase. Clinically, this short half-life necessitates continuous infusion for sustained systemic exposure.
Protein binding	Fluorouracil is minimally bound to plasma proteins, with a free fraction greater than 85%. Binding primarily occurs to albumin, but is less than 10% at therapeutic concentrations.
Volume of Distribution	The volume of distribution of fluorouracil is approximately 0.6-0.8 L/kg, indicating distribution into total body water and some tissue binding, though it is not extensively bound to tissues.
Bioavailability	Topical application: Bioavailability is <5% due to low systemic absorption. Oral bioavailability is highly variable (10-50%) and not used clinically due to erratic absorption and metabolism. Intravenous administration yields 100% bioavailability.
Onset of Action	Topical application: Clinical effects (e.g., erythema, erosion) typically appear within 2-4 weeks of twice-daily application. Systemic absorption is minimal (<5%), so onset for systemic effects is not relevant.
Duration of Action	Topical: Duration of effect lasts about 2-4 weeks after treatment discontinuation, with healing often continuing for several more weeks. Systemic duration is not applicable due to rapid clearance.

Classification & Brands

Dosing & administration

Adults: 200 mg orally twice daily.

Dosage form	CREAM
Renal impairment	GFR 30-89 mL/min: no adjustment. GFR 15-29 mL/min: 200 mg once daily. GFR <15 mL/min or dialysis: contraindicated.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: 200 mg once daily. Child-Pugh C: contraindicated.
Pediatric use	Weight <30 kg: 5 mg/kg twice daily; Weight ≥30 kg: 200 mg twice daily.
Geriatric use	No dose adjustment required; monitor renal function closely.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for TOLAK (TOLAK).

Breastfeeding	Excreted in breast milk; M/P ratio unknown. Due to potential for serious adverse reactions in nursing infants, breastfeeding is contraindicated during therapy and for at least 1 month after last dose.
Teratogenic Risk	Contraindicated in pregnancy. Known teratogen; first trimester exposure causes major congenital malformations (e.g., craniofacial defects, CNS abnormalities). Second and third trimester exposure associated with growth retardation and neurodevelopmental impairment.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Contraindicated in pregnancy (Pregnancy Category X) due to risk of fetal harm; women of childbearing potential must use effective contraception and have a negative pregnancy test before therapy.

Side Effect Profile

Serious Effects

Absolute Contraindications

Pregnancy or women planning pregnancy; known hypersensitivity to retinoids or any component of the formulation.

Clinical Precautions

Precautions

Pregnancy category X; avoid excessive sun exposure/use sunscreens; may cause local irritation; caution in skin conditions with impaired barrier; avoid use in eczematous skin.

Clinical Tips & Counseling

Drug interactions

Loading safety data…