ATRALIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ATRALIN (ATRALIN).
Retinoic acid receptor (RAR) agonist; binds to RARs (alpha, beta, gamma) to modulate gene transcription, regulating cell growth, differentiation, and apoptosis.
| Metabolism | Primarily hepatic via CYP450 enzymes (CYP2C8, CYP2C9, CYP2A6, CYP2B2, CYP2E1); also metabolized by UGTs (UGT1A9, UGT2B7). |
| Excretion | Primarily hepatic metabolism via CYP450 isoenzymes, with metabolites excreted in bile and urine. Approximately 60-70% of the dose is eliminated in feces (as unchanged drug and metabolites) and 15-25% in urine (mainly as metabolites). Less than 1% is excreted unchanged in urine. |
| Half-life | Terminal elimination half-life is approximately 1-2 hours in adults, but may be prolonged in patients with hepatic impairment or severe renal disease. Due to its short half-life and extensive protein binding, drug concentrations may not correlate directly with clinical response. |
| Protein binding | Highly protein bound (approximately 95-99%), primarily to albumin and alpha-1-acid glycoprotein. Binding is saturable and can be affected by other drugs or disease states, potentially altering free drug concentrations. |
| Volume of Distribution | Volume of distribution is approximately 0.3-0.6 L/kg, indicating distribution primarily into extracellular fluid and limited tissue penetration. This low Vd suggests minimal extravascular distribution, consistent with its high protein binding. |
| Bioavailability | Oral bioavailability is reported to be 40-60% due to first-pass metabolism. Topical bioavailability is negligible (<5%) when applied to intact skin, with systemic absorption increasing if applied to broken or diseased skin. |
| Onset of Action | Oral: Peak serum concentrations achieved within 1-2 hours; clinical effect typically seen within 2-4 hours. Topical: Onset of action varies; improvement in acne lesions observed within 4-8 weeks of regular application. IV: Rapid distribution, with pharmacological effects noted within 30-60 minutes. |
| Duration of Action | Oral: Duration of action is approximately 4-6 hours, requiring multiple daily dosing for sustained effect. Topical: Effects persist for 24 hours, but continuous application over weeks is necessary for therapeutic benefit. IV: Duration correlates with plasma levels; clinical effects diminish as drug is cleared, typically within a few hours. |
20-30 mg/m² orally once daily for 5 consecutive days, repeated every 4 weeks.
| Dosage form | GEL |
| Renal impairment | For GFR < 60 mL/min: reduce dose by 25%. For GFR < 30 mL/min: reduce dose by 50%. For dialysis: administer 50% dose post-dialysis. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated. |
| Pediatric use | 2-16 years: 20 mg/m² orally once daily for 5 days, repeat every 28 days. Maximum 30 mg/m² per dose. |
| Geriatric use | Start at 20 mg/m² orally once daily for 5 days; increase cautiously based on tolerance. Monitor renal function and adjust per GFR. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ATRALIN (ATRALIN).
| Breastfeeding | Contraindicated in breastfeeding; isotretinoin is excreted into human milk; M/P ratio not established but predicted to be low due to high protein binding (>99%); however, potential for adverse effects in nursing infant precludes use. |
| Teratogenic Risk | First trimester: Category X; isotretinoin is highly teratogenic with an estimated 20-35% risk of major fetal malformations including CNS, craniofacial, cardiovascular, and thymic defects; spontaneous abortion risk increased. Second and third trimesters: Continued risk of teratogenicity; fetal exposure should be avoided. Postnatal: Possible long-term neurodevelopmental effects. |
■ FDA Black Box Warning
ATRA can cause severe fetal harm; females of childbearing potential must have negative pregnancy test within 1 week before starting therapy and use effective contraception during and for 1 month after treatment.
| Serious Effects |
Hypersensitivity to ATRA or any component, known hypersensitivity to retinoids, severe leukopenia (e.g., WBC <1000/µL), pregnancy (category X), women of childbearing potential not using effective contraception, breastfeeding.
| Precautions | Differentiation syndrome (fever, dyspnea, pulmonary infiltrates, pleural/pericardial effusions, weight gain), leukocytosis, pseudotumor cerebri (especially in children), hepatotoxicity, hypertriglyceridemia, increased intracranial pressure, photosensitivity, lipid abnormalities. |
| Food/Dietary | Take with food (especially fatty meals) to enhance absorption. Avoid grapefruit juice. Avoid excessive intake of vitamin A-rich foods (e.g., liver, fortified cereals). |
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| Fetal Monitoring | Pregnancy testing: Baseline serum β-hCG before treatment, monthly during therapy, and 5 weeks after discontinuation. Contraceptive counseling: Two forms of effective contraception required 1 month before, during, and 1 month after therapy. Fetal monitoring: If pregnancy occurs, immediate discontinuation and referral for fetal assessment including high-resolution ultrasound. |
| Fertility Effects | Isotretinoin does not appear to have permanent effects on fertility in women; temporary menstrual irregularities have been reported. In males, no known effect on spermatogenesis based on limited data. |
| Clinical Pearls | Monitor for pseudotumor cerebri (headache, visual disturbances) especially when combined with tetracyclines. Avoid in pregnancy (X-rated) and in women of childbearing potential without two forms of contraception. Initiate therapy 2-3 days after meals; administer with food to improve absorption. Reduce dose in severe hepatic impairment. Contraindicated in hypervitaminosis A. |
| Patient Advice | Take this medication with meals to increase absorption and reduce GI upset. · Avoid pregnancy; use two effective contraceptive methods 1 month before, during, and 1 month after treatment. · Do not donate blood during therapy and for 1 month after discontinuation. · Report severe headache, visual changes, nausea, or vomiting immediately. · Avoid tetracycline antibiotics, vitamin A supplements, and alcohol. · May cause photosensitivity; use sunscreen and protective clothing. · Do not take extra vitamin A or multivitamins containing vitamin A. |