Scopolamine

Absorption

The pharmacokinetics of scopolamine differ substantially between different dosage routes. Oral administration of 0.5 mg scopolamine in healthy volunteers produced a Cmax of 0.54 ± 0.1 ng/mL, a tmax of 23.5 ± 8.2 min, and an AUC of 50.8 ± 1.76 ng*min/mL; the absolute bioavailability is low at 13 ± 1%, presumably because of first-pass metabolism. By comparison, IV infusion of 0.5 mg scopolamine over 15 minutes resulted in a Cmax of 5.00 ± 0.43 ng/mL, a tmax of 5.0 min, and an AUC of 369.4 ± 2.2 ng*min/mL.
Other dose forms have also been tested. Subcutaneous administration of 0.4 mg scopolamine resulted in a Cmax of 3.27 ng/mL, a tmax of 14.6 min, and an AUC of 158.2 ng*min/mL. Intramuscular administration of 0.5 scopolamine resulted in a Cmax of 0.96 ± 0.17 ng/mL, a tmax of 18.5 ± 4.7 min, and an AUC of 81.3 ± 11.2 ng*min/mL. Absorption following intranasal administration was found to be rapid, whereby 0.4 mg of scopolamine resulted in a Cmax of 1.68 ± 0.23 ng/mL, a tmax of 2.2 ± 3 min, and an AUC of 167 ± 20 ng*min/mL; intranasal scopolamine also had a higher bioavailability than that of oral scopolamine at 83 ± 10%.
Due to dose-dependent adverse effects, the transdermal patch was developed to obtain therapeutic plasma concentrations over a longer period of time. Following patch application, scopolamine becomes detectable within four hours and reaches a peak concentration (tmax) within 24 hours. The average plasma concentration is 87 pg/mL, and the total levels of free and conjugated scopolamine reach 354 pg/mL.

Toxicity

Scopolamine overdose may manifest as lethargy, somnolence, coma, confusion, agitation, hallucinations, convulsion, visual disturbance, dry flushed skin, dry mouth, decreased bowel sounds, urinary retention, tachycardia, hypertension, and supraventricular arrhythmias. In some cases, overdose symptoms may appear similar to those associated with withdrawal following discontinuation. However, withdrawal symptoms such as bradycardia, headache, nausea, abdominal cramps, and sweating can help to distinguish between these possibilities. Overdose management primarily involves the removal of all transdermal patch systems combined with symptomatic and supportive care. Ensuring an adequate airway, supplemental oxygen, establishing intravenous access, and continuous monitoring are recommended. In cases where patients have swallowed one or more patch systems, it may be necessary to remove them or administer activated charcoal.
Animal studies revealed an oral LD50 of 1880 mg/kg in mice and 1270 mg/kg in rats, and a subcutaneous LD50 of 1650 mg/kg in mice and 296 mg/kg in rats.

Description

Scopolamine is a type of alkaloid that exists in a variety of Solanaceae plants such as Scopolia japonica, Datura metel L., and so on. It is the main active ingredient in these plants.
Apart from scopolamine, several other chemical ingredients also exist in Scopolia japonica, including hyoscyamine, anisodamine, anisodine, and so on. Hyoscyamine is an inhibitor of parasympathetic nerve, with the analgesic and antispasmodic functions, especially for sciatica, sometimes for the treatment of epilepsy, seasickness, etc., and its pharmacological effects are similar to atropine. However, its clinical application is less because of its toxicity. The clinical applications of anisodamine are treating infectious toxic shock, vascular disorders, various neuralgia, smooth muscle spasms, vertigo, fundus disorders and sudden deafness, and other diseases. It has definite curative effect and is widely used in clinical in China. Its synthetic product is called “654-2,” which now still is an effective drug to treat infectious shock and other vascular diseases. While anisodine is used to treat vascular headache, retinal vasospasm, ischemic optic neuritis, cerebrovascular disease, acute paralysis, central dysfunction caused by carbon monoxide poisoning, tremor, paralysis, bronchial asthma, motion sickness, organophosphorus pesticide poisoning, and so on .

Description

Scopolamine?(1)?and its biochemical precursor hyoscyamine?(2)?are deadly-nightshade alkaloids that are also found other plants of the Solanaceae family such as mandrake, jimsonweed, and tomato. Hyoscyamine is the enantiomer of the well-known nightshade alkaloid atropine.
Both alkaloids are extremely poisonous and have hallucinogenic effects. (Mandrake is sometimes called “insane root”.) They are anticholinergics, and, when used in small doses, they have medical uses such as treating gastrointestinal disorders. Plant extracts containing them have been used medicinally and ritually since biblical times or earlier.
Scopolamine is used criminally to poison people, not only to murder them but also to make them vulnerable to robbery or rape. Despite its adverse effects, it also has been tried as a “truth drug”.

The Uses of Scopolamine

Scopolamine is used for practically the same indications as atropine, but it should be noted that it has a sedative effect on motor activity, and it is recommended for the treatment of Parkinsonian symptoms.

Indications

Scopolamine is indicated in adult patients for the prevention of nausea and vomiting associated with motion sickness and for the prevention of postoperative nausea and vomiting (PONV) associated with anesthesia or opiate analgesia.

Background

Scopolamine is a tropane alkaloid isolated from members of the Solanaceae family of plants, similar to atropine and hyoscyamine, all of which structurally mimic the natural neurotransmitter acetylcholine. Scopolamine was first synthesized in 1959, but to date, synthesis remains less efficient than extracting scopolamine from plants. As an acetylcholine analogue, scopolamine can antagonize muscarinic acetylcholine receptors (mAChRs) in the central nervous system and throughout the body, inducing several therapeutic and adverse effects related to alteration of parasympathetic nervous system and cholinergic signalling. Due to its dose-dependent adverse effects, scopolamine was the first drug to be offered commercially as a transdermal delivery system, Scopoderm TTS?, in 1981. As a result of its anticholinergic effects, scopolamine is being investigated for diverse therapeutic applications; currently, it is approved for the prevention of nausea and vomiting associated with motion sickness and surgical procedures.
Scopolamine was first approved by the FDA on December 31, 1979, and is currently available as both oral tablets and a transdermal delivery system.

Pharmacokinetics

Scopolamine is an anticholinergic belladonna alkaloid that, through competitive inhibition of muscarinic receptors, affects parasympathetic nervous system function and acts on smooth muscles that respond to acetylcholine but lack cholinergic innervation. Formulated as a patch, scopolamine is released continuously over three days and remains detectable in urine over a period of 108 hours. Scopolamine is contraindicated in angle-closure glaucoma and should be used with caution in patients with open-angle glaucoma due to scopolamine's ability to increase intraocular pressure. Also, scopolamine exhibits several neuropsychiatric effects: exacerbated psychosis, seizures, seizure-like, and other psychiatric reactions, and cognitive impairment; scopolamine may impair the ability of patients to operate machinery or motor vehicles, play underwater sports, or perform any other potentially hazardous activity. Women with severe preeclampsia should avoid scopolamine. Patients with gastrointestinal or urinary disorders should be monitored frequently for impairments, and scopolamine should be discontinued if these develop. Scopolamine can cause blurred vision if applied directly to the eye, and the transdermal patch should be removed before an MRI procedure to avoid skin burns. Due to its gastrointestinal effects, scopolamine can interfere with gastric secretion testing and should be discontinued at least 10 days before performing the test. Finally, scopolamine may induce dependence and resulting withdrawal symptoms, such as nausea, dizziness, vomiting, gastrointestinal disturbances, sweating, headaches, bradycardia, hypotension, and various neuropsychiatric manifestations following treatment discontinuation; severe symptoms may require medical attention.

Metabolism

Little is known about the metabolism of scopolamine in humans, although many metabolites have been detected in animal studies. In general, scopolamine is primarily metabolized in the liver, and the primary metabolites are various glucuronide and sulphide conjugates. Although the enzymes responsible for scopolamine metabolism are unknown, in vitro studies have demonstrated oxidative demethylation linked to CYP3A subfamily activity, and scopolamine pharmacokinetics were significantly altered by coadministration with grapefruit juice, suggesting that CYP3A4 is responsible for at least some of the oxidative demethylation.