Anticholinergic intoxication can occur with a wide variety of prescription and over-the-counter medications and with numerous plants and mushrooms. Common drugs that have anticholinergic activity include antihistamines, antipsychotics, antispasmodics, skeletal muscle relaxants, and tricyclic antidepressants. Common combination products containing anticholinergic drugs include Atrohist, Donnagel, Donnatal, Hyland's Teething Tablets, Lomotil, Motofen, Ru-Tuss, Urised, and Urispas. Common anticholinergic medications are described in Table II–5. Plants and mushrooms containing anticholinergic alkaloids include jimsonweed (Datura stramonium), deadly nightshade (Atropa belladonna), and fly agaric (Amanita muscaria).
TABLE II–5.ANTICHOLINERGIC DRUGSa ||Download (.pdf) TABLE II–5. ANTICHOLINERGIC DRUGSa
|Tertiary Amines ||Usual Adult Single Dose (mg) ||Quaternary Amines ||Usual Adult Single Dose (mg) |
|Atropine ||0.4–1 ||Anisotropine ||50 |
|Benztropine ||1–6 ||Clidinium ||2.5–5 |
|Biperiden ||2–5 ||Glycopyrrolate ||1 |
|Darifenacin ||7.5–15 ||Hexocyclium ||25 |
|Dicyclomine ||10–20 ||Ipratropium bromide ||N/Ab |
|Flavoxate ||100–200 ||Isopropamide ||5 |
|Fesoterodine ||4–8 ||Mepenzolate ||25 |
|L-Hyoscyamine ||0.15–0.3 ||Methantheline ||50–100 |
|Oxybutynin ||5 ||Methscopolamine ||2.5 |
|Oxyphencyclimine ||10 ||Propantheline ||7.5–15 |
|Procyclidine ||5 ||Tiotropium ||N/Ac |
|Scopolamine ||0.4–1 ||Tridihexethyl ||25–50 |
|Solifenacin succinate ||5–10 ||Trospium chloride ||20 |
|Tolterodine ||2–4 || || |
|Trihexyphenidyl ||6–10 || || |
Anticholinergic agents competitively antagonize the effects of acetylcholine at peripheral muscarinic and central receptors. Exocrine glands, such as those responsible for sweating and salivation, and smooth muscle are mostly affected. The inhibition of muscarinic activity in the heart leads to a rapid heartbeat.
Tertiary amines such as atropine are well absorbed centrally, whereas quaternary amines such as glycopyrrolate have a less central effect.
Pharmacokinetics. Absorption may be delayed because of the pharmacologic effects of these drugs on GI motility. The duration of toxic effects can be quite prolonged (eg, benztropine intoxication may persist for 2–3 days; see also Table II–66).
The range of toxicity is highly variable and unpredictable. The potentially lethal dose of atropine has been estimated to be greater than 10 mg in adults. Ingestion of 30–50 jimsonweed seeds has been reported to cause significant toxicity. Doses up to 360 mg of trospium chloride produced increased heart rate and dry mouth but no other significant toxicity in healthy adults.
The anticholinergic syndrome is characterized by warm, dry, flushed skin; dry mouth; mydriasis; delirium; tachycardia; ileus; and urinary retention. Jerky myoclonic movements and choreoathetosis are common and may lead to rhabdomyolysis. Hyperthermia, coma, and respiratory arrest may occur. Seizures are rare with pure antimuscarinic agents, although they may result from other pharmacologic properties of the drug (eg, tricyclic antidepressants and antihistamines).