Depending on the route of administration and the treated condition, the onset of action can be from two hours up to one or two days after application; and the drug can act much longer than its elimination half-life would suggest. Chemistry
Triamcinolone is a synthetic pregnane corticosteroid and derivative of cortisol (hydrocortisone) and is also known as 1-dehydro-9α-fluoro-16α-hydroxyhydrocortisone or 9α-fluoro-16α-hydroxyprednisolone as well as 9α-fluoro-11β,16α,17α,21-tetrahydroxypregna-1,4-diene-3,20-dione.The substance is a light-sensitive, white to off-white, crystalline powder, or has the form of colourless, matted crystals. It has no odour or is nearly odourless. Information on the melting point varies, partly due to the substances polymorphism: 260 to 263 °C (500 to 505 °F), 264 to 268 °C (507 to 514 °F), or 269 to 271 °C (516 to 520 °F) can be found in the literature.Solubility is 1:500 in water and 1:240 in ethanol; it is slightly soluble in methanol, very slightly soluble in chloroform and diethylether, and practically insoluble in dichloromethane.
The risk for blood count changes is increased when combining triamcinolone with ACE inhibitors.Triamcinolone and other drugs can also influence each others concentrations in the body, amounting to pharmacokinetic interactions such as:
Rifampicin, phenytoin, carbamazepine and other inducers of the liver enzyme CYP3A4 speed up metabolization of triamcinolone and can therefore reduce its effectiveness. Conversely, CYP3A4 inhibitors such as ketoconazole and itraconazole can increase its concentrations in the body and the risk for adverse effects. Blood concentrations of ciclosporin can be increased. Pharmacology
Mechanism of action
Triamcinolone is a glucocorticoid that is about five times as potent as cortisol, but has very little mineralocorticoid effects. Pharmacokinetics
When taken by mouth, the drugs bioavailability is over 90%. It reaches highest concentrations in the blood plasma after one to two hours and is bound to plasma proteins to about 80%. The biological half-life from the plasma is 200 to 300 minutes; due to stable complexes of triamcinolone and its receptor in the intracellular fluid, the total half-life is significantly longer at about 36 hours.A small fraction of the substance is metabolized to 6-hydroxy- and 20-dihydro-triamcinolone; most of it probably undergoes glucuronidation, and a smaller part sulfation. Three quarters are excreted via the urine, and the rest via the faeces.Due to corticoids mechanism of action, the effects are delayed as compared to plasma concentrations.