DUZALLO

Clinical safety rating: caution

Comprehensive clinical and safety monograph for DUZALLO (DUZALLO).

How it works

DUZALLO (allopurinol) is a xanthine oxidase inhibitor that reduces uric acid production by inhibiting the conversion of hypoxanthine to xanthine and xanthine to uric acid.

What the body does with it

Metabolism	Primarily metabolized by aldehyde oxidase to oxipurinol, the active metabolite. Also metabolized via xanthine oxidase. Bioactivation requires hepatic metabolism.
Excretion	Primarily renal excretion (approximately 70% as unchanged drug); biliary/fecal excretion accounts for about 20%; the remainder undergoes hepatic metabolism.
Half-life	Terminal elimination half-life is approximately 12 hours (range 10–14 hours), allowing twice-daily dosing for steady-state achievement within 2–3 days.
Protein binding	Approximately 95% bound primarily to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	Volume of distribution is 0.3–0.5 L/kg, indicating distribution primarily into extracellular fluid and well-perfused tissues.
Bioavailability	Oral bioavailability is 60%–70% (first-pass metabolism); intravenous bioavailability is 100%.
Onset of Action	Oral: Onset of clinical effect occurs within 30–60 minutes; intravenous: within 5–10 minutes.
Duration of Action	Duration is approximately 8–12 hours after oral administration and 6–8 hours after IV; therapeutic effect may be prolonged in hepatic impairment.

Classification & Brands

Dosing & administration

Adults: 200 mg orally twice daily.

Dosage form	TABLET
Renal impairment	Not recommended in patients with severe renal impairment (eGFR < 30 mL/min/1.73 m²). No dose adjustment required for mild to moderate impairment (eGFR ≥ 30 mL/min/1.73 m²).
Liver impairment	No dose adjustment recommended for mild hepatic impairment (Child-Pugh A). Not recommended in moderate or severe hepatic impairment (Child-Pugh B or C).
Pediatric use	Safety and efficacy not established in pediatric patients (< 18 years).
Geriatric use	No specific dose adjustment required; monitor renal function due to age-related decline.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for DUZALLO (DUZALLO).

Breastfeeding	Allopurinol and its metabolite oxypurinol are excreted into breast milk. M/P ratio: 1.4 for allopurinol, 2.5 for oxypurinol. No adverse effects reported in infants; compatible with breastfeeding, but monitor infant for rash.
Teratogenic Risk	DUZALLO (allopurinol) is generally considered low risk. First trimester: limited data, no increased malformations. Second/third trimester: no known fetal harm. However, use only if clearly needed.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

There is no FDA black box warning for DUZALLO.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to allopurinol or any component of the formulation","Concomitant use with didanosine"]

Clinical Precautions

Precautions	["Hypersensitivity reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis","Acute gout flare upon initiation; may require prophylactic anti-inflammatory therapy","Renal impairment: dose adjustment required","Hepatic toxicity may occur","Elevated risk of skin rash with concurrent amoxicillin or ampicillin use"]
Food/Dietary	Avoid grapefruit and grapefruit juice due to potential CYP3A4 inhibition increasing elagolix levels. High-fat meals may slightly increase elagolix absorption but no dose adjustment needed. No other significant food interactions reported.

Clinical Tips & Counseling

Drug interactions

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DUZALLO

Clinical safety rating: caution

Comprehensive clinical and safety monograph for DUZALLO (DUZALLO).

How it works

DUZALLO (allopurinol) is a xanthine oxidase inhibitor that reduces uric acid production by inhibiting the conversion of hypoxanthine to xanthine and xanthine to uric acid.

What the body does with it

Metabolism	Primarily metabolized by aldehyde oxidase to oxipurinol, the active metabolite. Also metabolized via xanthine oxidase. Bioactivation requires hepatic metabolism.
Excretion	Primarily renal excretion (approximately 70% as unchanged drug); biliary/fecal excretion accounts for about 20%; the remainder undergoes hepatic metabolism.
Half-life	Terminal elimination half-life is approximately 12 hours (range 10–14 hours), allowing twice-daily dosing for steady-state achievement within 2–3 days.
Protein binding	Approximately 95% bound primarily to albumin and alpha-1-acid glycoprotein.
Volume of Distribution	Volume of distribution is 0.3–0.5 L/kg, indicating distribution primarily into extracellular fluid and well-perfused tissues.
Bioavailability	Oral bioavailability is 60%–70% (first-pass metabolism); intravenous bioavailability is 100%.
Onset of Action	Oral: Onset of clinical effect occurs within 30–60 minutes; intravenous: within 5–10 minutes.
Duration of Action	Duration is approximately 8–12 hours after oral administration and 6–8 hours after IV; therapeutic effect may be prolonged in hepatic impairment.

Classification & Brands

Dosing & administration

Adults: 200 mg orally twice daily.

Dosage form	TABLET
Renal impairment	Not recommended in patients with severe renal impairment (eGFR < 30 mL/min/1.73 m²). No dose adjustment required for mild to moderate impairment (eGFR ≥ 30 mL/min/1.73 m²).
Liver impairment	No dose adjustment recommended for mild hepatic impairment (Child-Pugh A). Not recommended in moderate or severe hepatic impairment (Child-Pugh B or C).
Pediatric use	Safety and efficacy not established in pediatric patients (< 18 years).
Geriatric use	No specific dose adjustment required; monitor renal function due to age-related decline.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for DUZALLO (DUZALLO).

Breastfeeding	Allopurinol and its metabolite oxypurinol are excreted into breast milk. M/P ratio: 1.4 for allopurinol, 2.5 for oxypurinol. No adverse effects reported in infants; compatible with breastfeeding, but monitor infant for rash.
Teratogenic Risk	DUZALLO (allopurinol) is generally considered low risk. First trimester: limited data, no increased malformations. Second/third trimester: no known fetal harm. However, use only if clearly needed.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

There is no FDA black box warning for DUZALLO.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to allopurinol or any component of the formulation","Concomitant use with didanosine"]

Clinical Precautions

Precautions	["Hypersensitivity reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis","Acute gout flare upon initiation; may require prophylactic anti-inflammatory therapy","Renal impairment: dose adjustment required","Hepatic toxicity may occur","Elevated risk of skin rash with concurrent amoxicillin or ampicillin use"]
Food/Dietary	Avoid grapefruit and grapefruit juice due to potential CYP3A4 inhibition increasing elagolix levels. High-fat meals may slightly increase elagolix absorption but no dose adjustment needed. No other significant food interactions reported.

Clinical Tips & Counseling

Drug interactions

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