Antipsychotics : Long term use of trihexyphenidyl  may mask or increase the risk of tardive dyskinesia. Pethidine (meperidine) : Central effects and side effects of pethidine may be increased. Metoclopramide : Action of metoclopramide is decreased. Alcohol : Risk of serious intoxication. Pharmacology
The exact mechanism of action in parkinsonian syndromes is not precisely understood, but it is known that trihexyphenidyl blocks efferent impulses in parasympathetically innervated structures like smooth muscles (spasmolytic activity), salivary glands, and eyes (mydriasis). In higher doses direct central inhibition of cerebral motor centers may contribute. In very high doses central toxicity as seen in atropine overdose is noted. It binds to the M1 muscarinic receptor and possibly the dopamine receptor. Trihexyphenidyl is rapidly absorbed from the gastrointestinal tract. The onset of action is within 1 hour after oral dosing. The peak activity is noted after 2 to 3 hours. The duration of action of one single dose is 6 to 12 hours in a dose dependent manner. It is excreted in the urine, probably as unchanged drug. More precise data in animals and humans have so far not been determined. History
Artane, or its generic form Trihexyphenidyl HCL, was approved by the FDA on June 25, 2003 for the clinical use of all types of parkinsonism. However, it has been clinically relevant in trials pertaining to Parkinsons disease since 1949. Artane is an anticholinergic drug which is prescribed by doctors throughout the world. It is also abused, typically in combination with other drugs or delicate pharmaceutical agents.
Aneurysm of the aortic sinus, also known as the sinus of Valsalva, is a rare abnormality of the aorta, the largest artery in the body. The aorta normally has three small pouches that sit directly above the aortic valve (the sinuses of Valsalva), and an aneurysm of one of these sinuses is a thin-walled swelling. Aneurysms may affect the right (65–85%), non-coronary (10–30%), or rarely the left (< 5%) coronary sinus. These aneurysms may not cause any symptoms but if large can cause shortness of breath, palpitations or blackouts. Aortic sinus aneurysms can burst or rupture into adjacent cardiac chambers, which can lead to heart failure if untreated. Aortic sinus aneurysms may occur in isolation, or may been seen in association with other diseases of the aorta including Marfan syndrome, Loeys-Dietz syndrome, and bicuspid aortic valve. They can be diagnosed using an echocardiogram or cardiac magnetic resonance imaging (MRI) scan. Treatment includes blood pressure control but surgical repair may be needed, especially if the aneurysm ruptures. Symptoms and signs
If unruptured, sinus of Valsalva aneurysm (commonly abbreviated SVA or SOVA) is usually asymptomatic and typically goes undetected until symptoms appear or medical imaging is performed for other reasons. If symptoms do occur, the most common are shortness of breath, palpitations, myocardial ischemia, and syncope.