TARGRETIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TARGRETIN (TARGRETIN).
Selective retinoid X receptor (RXR) agonist that modulates gene expression involved in cell differentiation, proliferation, and apoptosis.
| Metabolism | Primarily metabolized by CYP3A4; also involves CYP2C8, CYP2C9, CYP2C19, and CYP2D6. |
| Excretion | Primarily metabolized in the liver via CYP3A4; elimination is mainly through hepatobiliary excretion into feces. Renal excretion is minimal (<3% as unchanged drug). |
| Half-life | Terminal elimination half-life is approximately 7 hours (range 3–10 hours) for the parent drug. The active metabolite (bexarotene glucuronide) has a half-life of about 9 hours. Clinically, steady state is reached within 3–5 days. |
| Protein binding | >99% bound primarily to albumin and lipoproteins. |
| Volume of Distribution | Approximately 0.3 L/kg (range 0.2–0.5 L/kg), indicating distribution mainly in the vascular compartment with limited tissue penetration. |
| Bioavailability | Oral bioavailability is approximately 60–90% when taken with food; high-fat meals increase absorption. Absolute bioavailability has not been determined due to lack of intravenous formulation. |
| Onset of Action | Oral: Clinical improvement (e.g., reduction of cutaneous lesions in cutaneous T-cell lymphoma) is typically observed within 4–8 weeks, but may begin as early as 2 weeks in some patients. |
| Duration of Action | Not well-defined due to chronic therapy; duration of effect is maintained with continuous daily dosing. Treatment is often continued until disease progression or unacceptable toxicity. |
| Molecular Weight | 348.48 |
300 mg/m2 orally once daily.
| Dosage form | GEL |
| Renal impairment | No specific dose adjustment recommended; use caution in severe renal impairment. |
| Liver impairment | Child-Pugh A: 300 mg/m2 daily; Child-Pugh B: reduce to 200 mg/m2 daily; Child-Pugh C: not studied, avoid use. |
| Pediatric use | Safety and efficacy not established; no standard dosing recommendations. |
| Geriatric use | No specific dose adjustments; monitor for adverse effects due to potential age-related decreased organ function. |
| 1st trimester | Contraindicated: Teratogenic risk based on animal data; avoid use. |
| 2nd trimester | Contraindicated: Potential fetal harm; use only if benefit outweighs risk. |
| 3rd trimester | Contraindicated: Risk of fetal harm; avoid unless maternal necessity. |
Clinical note
Comprehensive clinical and safety monograph for TARGRETIN (TARGRETIN).
| Placental transfer | Crosses placenta in animals; human data limited but expected to transfer. |
| Breastfeeding | Not recommended; potential for serious adverse effects in nursing infants. If use is essential, discontinue breastfeeding. |
| Lactation Rating | L5 (Contraindicated in lactating women) |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to bexarotene or any excipientPregnancyLactation
| Precautions | Hepatotoxicity: monitor LFTs, Posterior reversible encephalopathy syndrome (PRES), Hypertriglyceridemia: monitor lipids, Pancreatitis associated with hypertriglyceridemia, Hypothyroidism: monitor thyroid function, Leukopenia/neutropenia, Photosensitivity: avoid sun exposure |
| Food/Dietary | Take with a full meal containing fat (e.g., 30-50g fat) to improve bioavailability. Avoid grapefruit and grapefruit juice as they may increase drug levels. No other significant food interactions reported. |
| Clinical Pearls |
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| Teratogenic Risk | FDA Pregnancy Category D. Bexarotene is a known teratogen based on animal studies and its mechanism of action as a retinoid. There is positive evidence of human fetal risk, but potential benefits may warrant use in pregnant women despite potential risks. First trimester exposure is associated with high risk of major congenital malformations including craniofacial, cardiac, and central nervous system defects. Second and third trimester exposure may lead to fetal growth restriction and central nervous system effects. |
| Fetal Monitoring | Women of childbearing potential must have a negative serum pregnancy test within 1 week before starting therapy and monthly during treatment. Effective contraception must be used for 1 month before, during, and for at least 1 month after discontinuation. Monitor for signs of pancreatitis and hepatic dysfunction with monthly liver function tests and fasting lipid panels. Fetal ultrasonography should be considered if exposure occurs. |
| Fertility Effects | Bexarotene may impair fertility in males and females based on animal studies showing testicular degeneration and ovarian atrophy. Reversible decreases in sperm count and motility have been observed in preclinical studies. The effect on human fertility is unknown. |
| Targretin (bexarotene) is a retinoid X receptor (RXR) agonist used for cutaneous T-cell lymphoma (CTCL). Central hypothyroidism and hypertriglyceridemia are common; monitor TSH, free T4, and lipid panel at baseline and frequently. Start levothyroxine and lipid-lowering therapy (e.g., fenofibrate) prophylactically. Can cause photosensitivity; advise sun avoidance and sunscreen use. Dose adjustment for hepatic impairment; avoid in severe hepatic disease. |
| Patient Advice | Take with a fatty meal to enhance absorption; do not crush or chew capsules. · You will need regular blood tests to monitor thyroid function and cholesterol levels. · You must use effective contraception during treatment and for at least 1 month after stopping; bexarotene can cause fetal harm. · Avoid prolonged sun exposure and use sunscreen (SPF 30+) and protective clothing; this drug increases sensitivity to sunlight. · Report any new or worsening skin reactions, changes in vision, severe headache, or muscle pain to your healthcare provider. |