1 Read the text and render it according to the following aspects.

1. Antidiarrhoeal drugs (give examples).

2. The use of antidiarrhoeal drugs.

3. What is diarrhoea? Its causes.

4. Effect of antidiarrhoeal drugs on the bowel activity.

Antidiarrhoeal Drugs

Mesalazjne Morphine Olsalazine sodium Sodium cromoglycate Sulphasalazine

Codeine phosphate Colestyramine Co-phenotrope Kaolin

Loperamide hydrochloride

Antidiarrhoeal drugs are used selectively to:

• ease an acute episode of diarrhoea (e.g. infectious diarrhoea),

• help to control diarrhoea when it is caused by an underlying chro­nic disease or condition, such as inflammatory bowel disease.

Diarrhoea is a sign of disease. It occurs when the large bowel be­comes unable to properly process the contents of the alimentary tract. The inflamed or irritated colonic tissue stimulates the rapid passage of fluid, faecal matter into the rectum for expulsion.

Stools are passed more frequently, with greater fluidity and vol­ume.

Drugs to ease the diarrhoea may not be beneficial and may ulti­mately be harmful.

If selected, the choice of an antidiarrhoeal agent will depend on the condition causing the diarrhoea.

Antidiarrhoeal drugs are effective by countering the effects of dis­turbed colonic activity.

They work by:

• increasing the bulk of the stool passing through the large bowel,

• reducing the rate of peristalsis propelling the gut contents through the large bowel,

• reducing the inflammation or irritable state of the large bowel.

2. JRead the text and say whether the following statements are true or

false. Confirm your opinion.

1. These drugs increase smooth muscle spasm in the digestive tract.

2. The purpose of these drugs is to solve mechanical problems of

digestion in the lower gastrointestinal tract.

3. These drugs can either reduce or increase the rate and tone of the intestinal muscles.

Drugs Affecting Peristalsis

These drugs will be selected to improve disorders of motility along the digestive tract:

• to help the passage of food from the oesophagus to the stomach	• non-ulcer dyspepsia
• prevent a reflux of stomach contents into the oesophagus	• hiatus hernia
• to reduce smooth muscle spasm in the digestive tract	• infant colic
• to increase or decrease the transit time of food through the digestive tract

The purpose of these drugs will be to solve mechanical problems of digestion in the upper gastrointestinal tract. Under normal circum­stances food will pass through the oesophagus, stomach and duode­num at the correct rate, without backward flow and using painless contractions of the gut wall to give peristaltic, propulsive movements.

These drugs can reduce, or increase, the rate and tone of intestinal muscles, usually by interfering with the passage of nerve impulses to the target tissues.

The muscle tone of the digestive tract and peristaltic contractions are controlled by the parasympathetic nervous system. Acetylcholine and dopamine are the neurotransmitters that conduct chemical mes­sages between nerve endings and intestinal tissues.

Enhanced or diminished contraction of smooth muscle fibres in the walls and valves of the upper gastrointestinal tract, will give the required effect of the chosen drug.