3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexenyl) -nona-2,4,6,8-tetraenoic acid

Absorption
C max is approximately 347 ng/mL. T max is 1 or 2 h. Orally, tretinoin is well absorbed into systemic circulation.

Distribution
Vd is not yet determined. Tretinoin is more than 95% protein bound (primarily to albumin). Binding remains constant over the concentration range of 10 to 500 ng/mL.

Metabolism
CYP-450 (CYP3A4, 2C8, and 2E) enzymes have been implicated in the oxidative metabolism of tretinoin. Metabolites are 13-cis retinoic acid, 4-oxo trans retinoic acid, 4-oxo cis retinoic acid, 4-oxo trans retinoic acid glucuronide. Metabolites have been identified in plasma and urine. Tretinoin's activity is primarily caused by the parent drug. There is evidence that tretinoin induces its own metabolism.

Elimination
Tretinoin's t ½ is 0.5 to 2 h. 63% is excreted in urine and 31% in feces.

Peak
1 to 2 h.

Agents known to cause pseudotumor cerebri (eg, tetracycline)
The risk of this condition occurring may be increased.

Antifibrinolytic agents (eg, aminocaproic acid, aprotinin, tranexamic acid)
Fatal thrombotic complications have been reported.

Benzoyl peroxide, cosmetics with drying effects, resorcinol, salicylic acid, soaps, or sulfur
May result in significant skin irritation.

CYP-450
Elimination may be altered by agents that inhibit or induce CYP-450 enzymes.

Photosensitizers (eg, fluoroquinolones, phenothiazines, sulfonamides, tetracyclines, thiazide diuretics)
May augment photosensitivity.

Vitamin A
Because symptoms of hypervitaminosis A may be exacerbated, do not give with vitamin A.