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Anticholinergics: Mechanism of Action, Side Effects and Contraindications

• Anticholinergics: general pharmacology
• Anticholinergics: trospium chloride
• Anticholinergics: oxybutynin
• Anticholinergics: tolterodine
• Anticholinergics: fesoterodine
• Anticholinergics: propiverine
• Anticholinergics: darifenacin
• Anticholinergics: solifenacin
• Anticholinergics: butylscopolamine

Mechanism of Action of Anticholinergic Drugs

Anticholinergic drugs act as antagonists on cholinergic (=muscarinic) receptors. Five muscarinic receptor subtypes (M₁ to M₅) have been identified so far. The bladder has mainly M₂ (80%) and M₃ (20%) cholinergic receptor types, but only the M₃ receptor is responsible for parasympathetic detrusor contraction (see section bladder physiology. The inhibition of M₃ receptors with anticholinergics reduces smooth muscle detrusor contraction, increases functional bladder capacity, and alleviates urgency symptoms.

Urological Indications for Anticholinergics:

• Autonomous detrusor contractions in neurogenic lower urinary tract dysfunction
• Overactive bladder
• Urge incontinence, urge symptoms in diseases like BPH, bladder infection, pelvic floor insufficiency, bladder catheterization ...
• Enuresis with urge symptoms

Side Effects of Anticholinergics

Muscarinic receptors are present in numerous organs, M₃ receptors are mainly found in smooth muscle and glands. The lack of organ specificity of anticholinergic drugs leads to a high rate of unwanted side effects.

Eye:

• Mydriases
• Disturbed accommodation
• Dry eyes due to inhibited lacrimal gland
• Risk of increased intraocular pressure in patients with glaucoma

Gastrintestinal tract:

• Dry mouth due to inhibited salivary glands
• Inhibition of intestinal motility (constipation)

Heart:

• Tachycardia

CNS:

• Dizziness, loss of concentration, drowsiness
• Aggravation of dementia
• Headache
• Fear, anxiety and confusion are possible psychiatric side effects.

Skin:

• Dry skin due inhibited sweat glands, impaired temperature regulation in fever.

Drug Interactions of Anticholinergics

Increased anticholinergic effect with antiparkinson drugs, antihistamines, antipsychotics, and tricyclic antidepressants. Amplification of the tachycardic effect of sympathomimetic drugs. Anticholinergics mitigate the effects of gastrointestinal prokinetics.

Contraindications of Anticholinergics

• Risk of urinary retention
• Narrow angle glaucoma
• Ileus, gastrointestinal stenosis
• Myasthenia gravis
• Tachyarrhythmias
• Dementia

References

Ouslander 2004 OUSLANDER, J. G.: Management of overactive bladder.
In: N Engl J Med
350 (2004), Nr. 8, S. 786–99

Yoshimura und Chancellor 2002 YOSHIMURA, N. ; CHANCELLOR, M. B.: Current and future pharmacological treatment for overactive bladder.
In: J Urol
168 (2002), Nr. 5, S. 1897–913

  Deutsche Version: Anticholinergika

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