Products
Parasympatholytics are commercially available, for example, in the form of tablets, capsules, solutions, as inhalation preparations, injection solutions, and eye drops. This article refers to antagonists at muscarinic acetylcholine receptors. Antagonists at nicotinic acetylcholine receptors, such as ganglion blockers, are discussed separately.
Structure and properties
Many parasympatholytics are structurally derived from atropine, a natural tropane alkaloid found in nightshade plants such as belladonna.
Effects
Parasympatholytics have anticholinergic (parasympatholytic) properties. They abolish the effects of acetylcholine on neurons and the effector organs by competitive antagonism. Thus, they exert effects opposite to those of the parasympathetic nervous system, a portion of the autonomic nervous system. Their effects include:
- Dilation of the pupil
- Secretion inhibition: salivary, bronchial, gastric and pancreatic secretion.
- Bronchodilatation
- Inhibition of intestinal activity, constipation
- Cramp relief
- Urinary retention
- Increase in heart rate
- Central effects
Parasympatholytics cause a decrease in smooth muscle tone. This affects the vascular muscles, bronchial and intestinal muscles, and the muscles of the draining biliary and urinary tracts. Agents differ in selectivity for M-receptor subtypes and in peripheral and central vagolysis, among other factors.
Indications
Indications for the use of parasympatholytics include (selection):
- Hyperactive bladder, bedwetting
- Smooth muscle spasms, hypersecretion, and hypermotility in the gastrointestinal and genitourinary tracts
- Asthma, COPD
- Parkinson’s disease
- Bradycardia
- Motion sickness
- Diagnosis of the back of the eye
- Vasomotor rhinitis
- As an antidote in poisoning
Dosage
According to the professional information. The drugs are administered both topically and systemically.
Abuse
Parasympatholytics are abused as hallucinogenic intoxicants. This is not advised because of the health risks.
Active ingredients
Drugs used for the treatment of hyperactive bladder:
- Clidinium bromide (Librax).
- Darifenacin (Emselex)
- Desfesoterodine (Tovedeso)
- Fesoterodine (Toviaz)
- Oxybutynin (e.g., ditropan)
- Propiverine (Mictonorm)
- Solifenacin (Vesicare, generic).
- Tolterodine (Detrusitol, generic).
- Trospium chloride (Spasmo-Urgenin Neo).
Inhalation preparations:
- Aclidinium bromide (Bretaris Genuair, Eklira Genuair).
- Glycopyrronium bromide (Seebri)
- Ipratropium bromide (Atrovent)
- Tiotropium bromide (Spiriva)
- Umeclidinium bromide (Anoro Ellipta)
Spasmolytics:
- Drofenin (Lunadon, not commercially available in many countries).
- Metixen (Spasmo-Canulase, out of commerce).
- Pirenzepine (out of commerce)
- Scopolamine butylbromide (buscopan)
Antiparkinsonian drugs:
- Biperiden (Akineton)
- Procyclidine (kemadrin)
Eye drops:
- Atropine (various suppliers)
- Scopolamine (Scopolamine Dispersa)
- Tropicamide (Mydriaticum Dispersa)
Phytopharmaceuticals:
- Nightshade plants such as belladonna and datura.
Other:
- Various antidepressants, neuroleptics and antihistamines are characterized by an anticholinergic component of action and also cause corresponding adverse effects.
Contraindications
Examples:
- Hypersensitivity
- Urinary retention
- Narrow-angle glaucoma
- Intestinal obstruction
- Tachyarrhythmia
For complete precautions, see the drug label.
Interactions
When anticholinergic agents and certain cardiac agents are combined, adverse effects are reciprocally enhanced. Due to slowed intestinal transit, absorption of pharmaceutical agents may be affected.
Adverse effects
Possible adverse effects include:
- Accommodative dysfunction, visual disturbances.
- Dry mouth
- Constipation and other gastrointestinal disorders.
- Urinary behavior
- Reduced sweat secretion
- Tachycardia (increased heart rate)
- Central disorders such as drowsiness, restlessness, agitation, anxiety, hallucinations, cognitive impairment, and confusion
- Sleep disturbances and fatigue
Children and the elderly are at higher risk for developing side effects.
