Drug interactions are mainly pharmacodynamic, that is, they result from other drugs either adding to triamcinolone's corticoid side effects or working against its desired effects. They include: Atropine and other anticholinergics can substantially increase pressure in the eyes. Antidiabetic drugs can become less effective because triamcinolone causes diabetes-like symptoms. Aspirin and other NSAIDs, as well as anticoagulants such as warfarin, add to the risk of gastrointestinal bleeding. Diuretics that excrete potassium (such as loop diuretics and thiazides) can increase the risk of hypokalemia and thus lead to abnormal heart rhythm. Cardiac glycosides may have more adverse effects due to reduced potassium levels in the blood. The risk for blood count changes is increased when combining triamcinolone with ACE inhibitors. Triamcinolone and other drugs can also influence each other's 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 drug's 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. 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