- Mechanism of Action
- Clinical Uses & Dosing
- Overdose and Central Anticholinergic Syndrome
Scopolamine combines reversibly (competitve antagonism) with muscarinic cholinergic receptors and thus prevents access of the neurotransmitter acetylcholine to these site. It is thus termed an anticholinergic.
IV Administration: onset of action about 2-3 minutes.
Scopolamine, like atropine, is a lipid soluble tertiary amine, and thus easily crosses the blood-brain barrier, causing CNS effects of sedation and delerium, esp. in the elderly (See Central Anticholinergic Syndrome).
- Determining the "Correct" Patient Weight to use for Drug Calculations
- In Combination with Anticholinesterase Drugs:
- Anti-Sialagogue Effect
- -Scopolamine is the most potent of the common anticholinergics for inhibiting salivation (see table above)
- -dose Adult: 0.4mg (400 mcg)
- Treatment of Reflex-Mediated Bradycardia
- -Scopolamine is the least effective of the common anticholinergics to treat an intraoperative bradycardia
- -Atropine is the anticholinergic of choice for treating an intraoperative bradycardia
- Preoperative Medication
- -much less frequently used now. Was given for sedation and antisialogogue effects.
- - Adults: 0.4 - 0.6 mg IM
- "Light" Anesthesia: to produce Amnesia
- -In emergency situations (shock) where clinical conditions dictate a minimal amount of traditional anesthetics and analgesics, some clinicians will give a dose of scopolamine 0.4mg IV, with the hope that recall or awareness will be minimized. Evidence for effectiveness is purely anecdotal, but is based on the prior use of scopolamine for women in labor (in the early 1970's), who had minimal-to-no recall of their birthing experience. (TVL).
- Motion-Induced Nausea; Narcotic-Induced Nausea
- - Transdermal absorption of scopolamine provides sustained therapeutic plasma concentrations that protect against motion-induced nausea, without introducing prohibitive side effects such as sedation, cycloplegia, or drying of secretions. For example, a postauricular application of scopolamine delivers the drug at about 5 ug/hour for 72 hours (total absorbed dose is <0.5 mg). Protection against motion-induced nausea is greatest if the transdermal application of scopolamine is initiated at least 4 hours before the noxious stimulus. Administration of transdermal scopolamine after the onset of symptoms is less effective than prophylactic administration.
- -Similar protection against motion-induced nausea by oral or IV administration of scopolamine would require large doses, resulting in undesirable side effects and subsequent poor patient acceptance.
-Transdermal application of a scopolamine patch has been shown to exert significant antiemetic effects in patients experiencing motion sickness and in those treated with patient-controlled analgesia or epidural morphine for the management of postoperative pain (Honkavaara et al, 1994; Kotelko et al., 1989; Loper et al., 1989). It is well known that motion sickness is caused by stimulation of the vestibular apparatus. It has also been shown that morphine and synthetic opioids increase vestibular sensitivity. It is presumed that scopolamine blocks transmission to the medulla of impulses arising from overstimulation of the vestibular apparatus of the inner ear. Indeed, application of a scopolamine patch before the induction of anesthesia protects against nausea and vomiting after middle ear surgery that is likely to alter function of the vestibular apparatus (Honkavaara et al., 1994). Furthermore, a prophylactic transdermal scopolamine patch applied the evening before surgery decreases but does not abolish the occurrence of nausea and vomiting after outpatient laparoscopy using general anesthesia (Bailey et al.,1990). Conversely, not all reports describe an antiemetic effect in patients treated with transdermal scopolamine who are undergoing general anesthesia (Koski et al., 1990).
- -Anisocoria associated with scopolamine has been attributed to contamination of the eye after digital manipulation of the transdermal scopolamine patch (Price, 1985). More than 90% of unilateral dilated pupils occur on the same side as the patch. This diagnosis is confirmed by history and failure of the mydriasis to respond to topical installation of pilocarpine.