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Hyoscyamine: Wikis


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Systematic (IUPAC) name
(8-methyl-8-azabicyclo[3.2.1]oct-3-yl) 3-hydroxy-2-phenyl-propanoate
CAS number 101-31-5
ATC code A03BA03
PubChem 3661
DrugBank APRD00607
ChemSpider 10246417
Chemical data
Formula C 17H23NO3  
Mol. mass 289.375 g/mol
Pharmacokinetic data
Bioavailability 50% Protein binding
Metabolism Hepatic
Half life 3-5 hrs.
Excretion Urine
Therapeutic considerations
Pregnancy cat. C
Legal status Prescription only (US)
Routes Oral, Injection
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Hyoscyamine, pronounced hee-oh-skee-ah-meen, is a chemical compound, a tropane alkaloid. It is the levorotary isomer to atropine. It is a secondary metabolite found in certain plants of the Solanaceae family, including henbane (Hyoscyamus niger), mandrake (Mandragora officinarum), jimsonweed (Datura stramonium), and deadly nightshade (Atropa belladonna).

Brand names for hyoscyamine include Symax, HyoMax, Anaspaz, Buwecon, Cystospaz, Levsin, Levbid, Levsinex, Donnamar, NuLev, Spacol T/S, Buscopan (containing the derivative hyoscine-N-butylbromide), Hyospasmol (also hyoscine-N-butylbromide) and Neoquess.



Hyoscyamine is used to provide symptomatic relief to various gastrointestinal disorders including spasms, peptic ulcers, irritable bowel syndrome, pancreatitis, colic and cystitis. It has also been used to relieve some heart problems, control some of the symptoms of Parkinson's disease, as well as for control of respiratory secretions in palliative care. It is may be useful in pain control for neuropathic pain treated with opioids as it increases the level of analgesia obtained. Several mechanisms are thought to contribute to this effect. The closely related drugs atropine and scopolamine and other members of the anticholinergic drug group like cyclobenzaprine, trihexyphenidyl, and orphenadrine are also used for this purpose. When hyoscyamine is used along with opioids or other anti-peristaltic agents, measures to prevent constipation are especially important given the risk of paralytic ileus.

Side effects

Side effects include dry mouth and throat, eye pain, blurred vision, restlessness, dizziness, arrythmia, flushing, and faintness. An overdose will cause headache, nausea, vomiting, and central nervous system symptoms including disorientation, hallucinations, euphoria, sexual arousal, short-term memory loss, and possible coma in extreme cases. Some people can experience transient combativeness. The euphoric and sexual effects are stronger than those of atropine but weaker than those of scopolamine, as well as dicycloverine, orphenadrine, cyclobenzaprine, trihexyphenidyl (street name Sexy Trihexy), ethanolamine antihistamines like phentyltoloxamine and the like


Hyoscyamine is an anticholinergic, specifically an antimuscarinic, working by blocking the action of acetylcholine at parasympathetic sites in smooth muscle, secretory glands and the CNS; increases cardiac output, dries secretions, and antagonizes serotonin. At comparable doses, hyoscyamine has 98 per cent of the anticholinergic power of atropine and the other major belladonna-derived drug scopolamine having 92 per cent of the antimuscarinic potency of atropine.


Hyoscyamine can be extracted from plants of the Solanaceae family, notably Datura stramonium. Empirically it is C17H23NO3. Its structural name is α-(hydroxymethyl)-, 8-methyl-8-azabicyclo[3.2.1]oct-3-yl ester, [3(S)-endo]-1αH,5αH-Tropan-3α-ol. Do not crush, chew, or divide the extended-release capsules, otherwise, an overdose will result.


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