Antimuscarinics and other Gut Antispasmodics

Antispasmodics are used to treat irritable bowel syndrome (IBS) and diverticular disease. They include:

Antimuscarinics (anticholinergics)

These act as smooth muscle relaxants, reducing gut spasm and intestinal motility. They include atropine sulphate, dicycloverine hydrochloride, and propantheline bromide and hyoscine butylbromide. They are poorly selective for gut smooth muscle and so antimuscarinic side-effects are common.
Dicycloverine hydrochloride has much less antimuscarinic action than atropine and also has some direct action on smooth muscle making it preferable to atropine which commonly causes antimuscarinic side-effects.
Propantheline bromide is an alternative to hyoscine butylbromide but is prescription only and has not been studied in IBS.^1,2

Alverine, mebeverine and peppermint oil

These are thought to have a direct inhibitory effect on smooth muscle. Their selectivity means there are relatively few side-effects.^1,2

Irritable bowel syndrome

• Management of patients with IBS includes reassurance and explanation, lifestyle modifications (reducing dietary fat, caffeine avoiding dietary triggers; exercise and altering defecation patterns), non-pharmacological therapies (education, coping strategies, relaxation therapies, hypnotherapy, cognitive behaviour therapy, biofeedback training) and pharmacological therapies.^2,3,4
• The British Society of Gastroenterologists (BSG) advises that current drug treatments are of limited value but that specific symptoms may respond in some patients to particular drugs.³ Predominant symptoms (abdominal pain, diarrhoea or constipation) should be used to guide drug selection.³ Antispasmodics are selected where abdominal pain is the chief complaint and there is evidence of their benefit in reducing pain and patients' overall assessment of their IBS symptoms.^5,6,7
• A Cochrane Review⁸ failed to determine if any one antispasmodic was more effective than another but BSG suggest that anticholinergic antispasmodics are slightly more effective than other antispasmodics. Antidepressants (tricyclics) are currently the most effective drugs for treating IBS and seretonergic drugs are under development but not available in the UK as yet.³

Diverticular disease⁹

Antispasmodics such as mebeverine, alverine and peppermint oil are sometimes used for pain-relief in diverticular disease. However, there is no good evidence for their efficacy. IBS and diverticular disease can be hard to distinguish clinically and antispasmodics may be of some use where there are symptoms suggestive of IBS (such as abdominal pain related to defecation, abdominal bloating or rectal mucus).

• Antimuscarinics should not be used in narrow-angle glaucoma, myasthenia gravis, paralytic ileus, megacolon, pyloric stenosis and prostatic enlargement
• Alverine and mebeverine should not be used in paralytic ileus, intestinal obstruction, faecal impaction, colonic atony or porphyria
• Antimuscarinics should be used with caution in those with a tachycardia (eg. hyperthyroidism, cardiac insufficiency or failure)
• Antimuscarinics should be used with care in those with Down's syndrome, in children and the elderly as these patient groups are more susceptible to side-effects
• Antimuscarinics should be used with caution in gastro-oesophageal reflux disease, diarrhoea, ulcerative colitis, acute MI and hypertension
• Pregnancy and breastfeeding

• Predictable antimuscarinic side-effects include: constipation, blurred vision, urinary retention, tachycardia, dry mouth, flushing and dryness of the skin. Confusion, nausea, vomiting and giddiness occur less commonly but are more likely to affect the elderly. These side-effects are generally mild and self-limiting with hyoscine butylbromide.
• Alverine and mebeverine can cause flatulence and bloating. These side-effects usually diminish during continued treatment.
• Peppermint oil can cause heartburn and perianal irritation. Capsules should be swallowed, not broken or chewed as the oil can directly irritate the mouth or oesophagus.

• Discuss the limitations of current drug treatments for IBS. Antispasmodics may be helpful to some individuals - in particular those where abdominal pain predominates symptoms. Patients should see drug therapy as one component of treatment.
• Advise antispasmodics may be used on "as required" basis or up to three times a day for acute attacks of pain or before meals if postprandial symptoms predominate.
• There is no consensus as to duration of treatment - most trials to date have been short (less than 2 months).
• Where there is no response to one anti-spasmodic, it is worth considering a switch to another - different agents may suit different individuals.