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Trade names | Artane, Parkin, Pacitane, Hexymer |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682160 |
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Routes of administration | Oral, as tablet or elixir |
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Elimination half-life | 3.3-4.1 hours |
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ECHA InfoCard | 100.005.105 |
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Formula | C20H31NO |
Molar mass | 301.474 g·mol−1 |
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Trihexyphenidyl (THP, benzhexol, trihex, marketed as Artane and others) is an antispasmodic drug used to treat stiffness, tremors, spasms, and poor muscle control. It is an agent of the antimuscarinic class and is often used in management of Parkinson's disease. It was approved by the FDA for the treatment of Parkinson's in the US in 2003. [2] [3]
It is on the World Health Organization's List of Essential Medicines. [4]
Trihexyphenidyl is used for the symptomatic treatment of Parkinson's disease in mono and combination therapy. [5] It is active in postencephalitic, arteriosclerotic, and idiopathic forms. The drug is also commonly used to treat extrapyramidal side effects occurring during antipsychotic treatment. It reduces the frequency and duration of oculogyric crises as well as of dyskinetic movements and spastic contractions. Trihexyphenidyl may improve psychotic depression and mental inertia frequently associated with Parkinson's disease and symptomatic problems caused by antipsychotic treatment.[ medical citation needed ] The drug cannot cure Parkinson's disease, but may provide substantial alleviation of symptoms. An estimated 50–75% of people with Parkinson's disease will react positively and experience a 20–30% symptomatic improvement. To increase therapeutic activity, trihexyphenidyl is often given concomitantly with levodopa or other antimuscarinic or antihistaminic (e.g. diphenhydramine) agents. Combination therapy with dopamine agonists such as cabergoline is also possible. This is often termed a 'multidimensional approach'.[ medical citation needed ]
Trihexyphenidyl has also been prescribed for essential tremor and akathisia. [6] [7]
In pediatrics, it has been used for children with dystonia due to cerebral palsy, [8] [9] [10] and to control drooling. [11]
In organophosphate poisoning, trihexyphenidyl is a more effective antidote than atropine to counteract the cholinergic crisis, seizures, and neuropathology. [12]
Equivocal preliminary results from small studies exist for other dyskinesias, Huntington's chorea, Spasmodic torticollis.[ medical citation needed ]
Contraindications include according to the Therapeutic Goods Administration Australia from 2022: [13]
Dose-dependent side effects are frequent, but typically lessen over time as the body adapts to the medication. All of the following symptoms considered, Artane has been shown to dramatically and consistently improve neurologic defects in people aged 16–86 over the course of five years. [14] People who are older or who have psychiatric conditions may become confused or develop delirium. Side effects include but are not limited to: [15]
Trihexyphenidyl is a pregnancy category C drug. It is advised to only use with caution if benefits outweigh risks. [17]
This section needs more reliable medical references for verification or relies too heavily on primary sources .(May 2017) |
Trihexyphenidyl and other antiparkinsonian drugs are known to be substances of abuse. This is true both in abusers of other substances and in chronic schizophrenics, the latter being infrequent abusers of other drugs. [18]
Overdose mimics an atropine intoxication with dryness of mucous membranes, red face, bowel and bladder paralysis, and hyperthermia in high doses. Central nervous system consequences are agitation, confusion, and hallucinations. An untreated overdose may be fatal, particularly in children. Premortal signs are respiratory depression, arrhythmia and cardiac arrest.
A specific antagonist is physostigmine, which combines a peripheral and a central action.
Carbachol can be used to treat atonic bowel and bladder. It may be necessary to treat hyperthermia with cooling blankets.
A case report of 24 hour long arrhythmia was treated with verapamil. [19]
Excessive myoclonus can be complicated by rhabdomyolysis; in one case risk was increased due to concomitant use of risperidone. [20]
This section needs more reliable medical references for verification or relies too heavily on primary sources .(May 2017) |
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 [21] and possibly the dopamine receptor.[ which? ] [22] 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. [23] 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. [24] [25]
Trihexyphenidyl has been clinically relevant in trials pertaining to Parkinson's disease since 1949. [26]
In the US, the FDA approved Artane, or its generic form Trihexyphenidyl HCL, only on June 25, 2003 for the clinical use of all types of parkinsonism. [27]
The neurologist Oliver Sacks reported using the drug recreationally in the 1960s. [28] He recalled taking "a large dose" knowing full well the drug was intended for people with Parkinson's. More recounts of Dr. Sacks' experiences — including experimentation with mescaline, psilocybin, LSD, and probably DMT [29] — have been compared in his book Hallucinations .
During the 1970s, trihexyphenidyl (trade name Parkan) was the most popular recreationally used prescription drug in Hungary. [30]
In a 2008 news report, trihexyphenidyl was seen to be used for recreational purposes among Iraqi soldiers and police, among other prescription drugs. The report states that the drugs were taken to relieve combat stress reaction. [31] Although that may be the case for some, others used Artane as a substitute or more intense version of LSD. This was especially prevalent in the 1960s, according to a report in "The New Yorker". Similarly to those in Iraqi forces, some of the appeal was that the individual may retain partial control while under the influence. [32]
Trihexyphenidyl can be synthesized in two ways, one linear and one convergent synthesis.
In the first way, the initial 2-(1-piperidino)propiophenone is synthesized in turn by the aminomethylation of acetophenone using paraformaldehyde and piperidine in a Mannich reaction. In the second step the 2-(1-piperidino)propiophenone is reacted with cyclohexylmagnesium bromide in a Grignard reaction. [33]
Trihexyphenidyl has a chiral center and two enantiomers. Medications are racemates. [34]
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CAS number: 40520-25-0 | CAS number: 40520-24-9 |
Atropine is a tropane alkaloid and anticholinergic medication used to treat certain types of nerve agent and pesticide poisonings as well as some types of slow heart rate, and to decrease saliva production during surgery. It is typically given intravenously or by injection into a muscle. Eye drops are also available which are used to treat uveitis and early amblyopia. The intravenous solution usually begins working within a minute and lasts half an hour to an hour. Large doses may be required to treat some poisonings.
Haloperidol, sold under the brand name Haldol among others, is a typical antipsychotic medication. Haloperidol is used in the treatment of schizophrenia, tics in Tourette syndrome, mania in bipolar disorder, delirium, agitation, acute psychosis, and hallucinations from alcohol withdrawal. It may be used by mouth or injection into a muscle or a vein. Haloperidol typically works within 30 to 60 minutes. A long-acting formulation may be used as an injection every four weeks by people with schizophrenia or related illnesses, who either forget or refuse to take the medication by mouth.
Drooling, or slobbering, is the flow of saliva outside the mouth. Drooling can be caused by excess production of saliva, inability to retain saliva within the mouth, or problems with swallowing.
Benzatropine (INN), known as benztropine in the United States and Japan, is a medication used to treat movement disorders like parkinsonism and dystonia, as well as extrapyramidal side effects of antipsychotics, including akathisia. It is not useful for tardive dyskinesia. It is taken by mouth or by injection into a vein or muscle. Benefits are seen within two hours and last for up to ten hours.
Hyoscyamine is a naturally occurring tropane alkaloid and plant toxin. It is a secondary metabolite found in certain plants of the family Solanaceae, including henbane, mandrake, angel's trumpets, jimsonweed, the sorcerers' tree, and Atropa belladonna. It is the levorotary isomer of atropine and thus sometimes known as levo-atropine.
An antispasmodic is a pharmaceutical drug or other agent that suppresses muscle spasms.
Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremors in parkinsonism, and nausea. It is taken by mouth, injected into a vein, injected into a muscle, or applied to the skin. Maximal effect is typically around two hours after a dose, and effects can last for up to seven hours.
Anticholinergics are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central and peripheral nervous system.
Ipratropium bromide, sold under the trade name Atrovent among others, is a type of anticholinergic medication which is applied by different routes: inhaler, nebulizer, or nasal spray, for different reasons.
Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. It may also be used for hiccups and muscle spasms near the end of life, and off-label to treat alcohol use disorder or opioid withdrawal symptoms. It is taken orally or by intrathecal pump. It is also sometimes used transdermally in combination with gabapentin and clonidine prepared at a compounding pharmacy.
Chlorprothixene, sold under the brand name Truxal among others, is a typical antipsychotic of the thioxanthene group.
Sulpiride, sold under the brand name Dogmatil among others, is an atypical antipsychotic medication of the benzamide class which is used mainly in the treatment of psychosis associated with schizophrenia and major depressive disorder, and sometimes used in low dosage to treat anxiety and mild depression. Sulpiride is commonly used in Asia, Central America, Europe, South Africa and South America. Levosulpiride is its purified levo-isomer and is sold in India for similar purpose. It is not approved in the United States, Canada, or Australia. The drug is chemically and clinically similar to amisulpride.
Biperiden, sold under the brand name Akineton among others, is a medication used to treat Parkinson disease, certain drug-induced movement disorders and Tourette Syndrome. It is not recommended for tardive dyskinesias. It is taken by mouth, injection into a vein, or muscle.
Procyclidine is an anticholinergic drug principally used for the treatment of drug-induced parkinsonism, akathisia and acute dystonia, Parkinson's disease, and idiopathic or secondary dystonia.
Extrapyramidal symptoms (EPS) are symptoms that are archetypically associated with the extrapyramidal system of the brain's cerebral cortex. When such symptoms are caused by medications or other drugs, they are also known as extrapyramidal side effects (EPSE). The symptoms can be acute (short-term) or chronic (long-term). They include movement dysfunction such as dystonia, akathisia, parkinsonism characteristic symptoms such as rigidity, bradykinesia, tremor, and tardive dyskinesia. Extrapyramidal symptoms are a reason why subjects drop out of clinical trials of antipsychotics; of the 213 (14.6%) subjects that dropped out of one of the largest clinical trials of antipsychotics, 58 (27.2%) of those discontinuations were due to EPS.
A muscarinic receptor antagonist (MRA), also called an antimuscarinic, is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. The muscarinic receptor is a protein involved in the transmission of signals through certain parts of the nervous system, and muscarinic receptor antagonists work to prevent this transmission from occurring. Notably, muscarinic antagonists reduce the activation of the parasympathetic nervous system. The normal function of the parasympathetic system is often summarised as "rest-and-digest", and includes slowing of the heart, an increased rate of digestion, narrowing of the airways, promotion of urination, and sexual arousal. Muscarinic antagonists counter this parasympathetic "rest-and-digest" response, and also work elsewhere in both the central and peripheral nervous systems.
Pimavanserin, sold under the brand name Nuplazid, is an atypical antipsychotic which is approved for the treatment of Parkinson's disease psychosis and is also being studied for the treatment of Alzheimer's disease psychosis, schizophrenia, agitation, and major depressive disorder. Unlike other antipsychotics, pimavanserin is not a dopamine receptor antagonist.
Acetylcholinesterase inhibitors (AChEIs) also often called cholinesterase inhibitors, inhibit the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine into choline and acetate, thereby increasing both the level and duration of action of acetylcholine in the central nervous system, autonomic ganglia and neuromuscular junctions, which are rich in acetylcholine receptors. Acetylcholinesterase inhibitors are one of two types of cholinesterase inhibitors; the other being butyryl-cholinesterase inhibitors. Acetylcholinesterase is the primary member of the cholinesterase enzyme family.
Flupentixol/melitracen is a combination of two psychoactive agents flupentixol and melitracen. It is designed for short term usage only. It is produced by Lundbeck.
Cholinergic blocking drugs are a group of drugs that block the action of acetylcholine (ACh), a neurotransmitter, in synapses of the cholinergic nervous system. They block acetylcholine from binding to cholinergic receptors, namely the nicotinic and muscarinic receptors.
This article incorporates public domain material from Toxnet:Trihexyphenidyl. United States Department of Health and Human Services . Retrieved 8 May 2017.