Antispasmodic Drugs

What are antispasmodics?

Antispasmodics are a class (group) of drugs that can help to control some symptoms that arise from the gut, in particular, gut spasm. There are two main types.

• Antimuscarinics such as dicycloverine, hyoscine, atropine, propantheline.
• Smooth muscle relaxants such as alverine, mebeverine and peppermint oil.

You can buy some antispasmodics from your pharmacist. However, most are only available with a prescription.

What conditions are they used to treat?

Antispasmodics are commonly used in irritable bowel syndrome (IBS):

• To help relieve some of the symptoms of IBS such as spasm (colic), bloating and abdominal (stomach) pain.
• To reduce the motility (movement) of the intestines (gut).

Note: not everybody with IBS finds that antispasmodics work well. However, they are worth trying as they work well in a good number of cases. Antispasmodics are also used in some other conditions such as diverticular disease.

How do antispasmodics work?

Your gut is partially controlled by an extensive network of neurons (cells of the nervous system). These help to regulate the motility (movement) of the gut. The neurons work by controlling smooth muscle which is present in the walls of the gut. It is this muscle which is responsible for gut movements.

The neurons are stimulated by various different chemicals produced by your body. These chemicals work by binding to special receptors (docking sites) on the muscle surface, which causes either relaxation or contraction of the smooth muscle. Contractions of the smooth muscle cause food in the gut to be moved further along the gut. However, in conditions such as IBS these contractions can occur too frequently or be painful, causing some of the symptoms experienced.

Antimuscarinics work by blocking muscarinic receptors. These are a class of receptors found in the gut which cause muscle contraction as described above. Blocking the receptors reduces the amount of contractions and should help to relieve some of the symptoms associated with IBS.

Because muscarinic receptors are also found in other parts of the body, taking an antimuscarinic can have other effects. For example, muscarinic receptors also help to control the production of saliva in the mouth. Taking a drug that blocks these receptors can cause a dry mouth.

Smooth muscle relaxants work directly on the smooth muscle in the wall of the gut. Here they help to relax the muscle and relieve the pain associated with a spasm (contraction) of the gut.

Which is the best one?

Current medical studies do not suggest one antispasmodic is more effective at relieving symptoms than another. Under the supervision of your doctor you may want to try different types to find the most effective one for you.

How do I take antispasmodics?

Your doctor will advise you how to take your medication including how often. You may be encouraged to use the drug at a particular time in relation to eating. It is generally recommended that you take these drugs only when necessary as continued use may make the drug less effective. For example, people with IBS commonly find that there are times when symptoms flare up for a while. So, it is common to take an antispasmodic when symptoms flare up, and to stop them if symptoms settle down. Read the leaflet that comes with your particular brand for further information.

How quickly do antispasmodics work?

Antispasmodics usually work within an hour or so to ease symptoms. Their effectiveness may depend on the dose you are given and how often you take them.

How long is treatment needed?

These drugs are usually only used when you have active symptoms. However this can vary depending on the reason for treating you. Your doctor should be able to advise you on this.

Who can and cannot take antispasmodics?

Most people can take antispasmodics. There are a few exceptions. A full list of people who should not take antispasmodics is included with the information leaflet that comes in the drug packet. If you are prescribed antispasmodics, read this to be sure you are safe to take it. In particular, antispasmodics may not be suitable for people with paralytic ileus, myasthenia gravis, pyloric stenosis and prostatic enlargement. Pregnant or breastfeeding mothers should also seek advice before using these drugs.

What about side-effects?

Most people who take antispasmodics do not have any serious side effects. If side effects occur, they are usually minor. The most common side effects are:

• Flatulence and bloating (wind)
• Heartburn
• Constipation
• Dry mouth

For a full list of all the side effects and possible interactions associated with your drug consult the leaflet that comes with your medication.

Other considerations

If you have IBS you may become used to having gut symptoms. However, do not assume all gut symptoms are due to your IBS. You should consult your doctor if you experience any change in the usual pattern of your symptoms. In particular, the following problems can indicate a serious gut disorder:

• Unintentional weight loss.
• Bleeding from the rectum (back passage).
• Blood in your stools (this may colour your stools (faeces) black).