Diarrhoea and ConstipationBy Priyanca Patel

What is Constipation?Infrequent bowel movements due to increased transit time or pelvic dysfunction

What factors could cause constipation?

• Age• Physiology• Medication

• Opioids• Anticholinergics• TCAs• CCBs

• Diet• Illness or

disorder• Hormonal

What treatment options are available for constipation?

Lifestyle: Changes in diet and exercise habits

Purgatives: accelerate transit of faeces through the intestine

What are the 4 main classes of purgatives?Faecal softeners

Osmotic laxatives

Bulk laxatives

Stimulant laxatives

Alter fecal consistency

Surface acting compounds

Act slowly (3-5 days) to keep stools soft

Used for constipation and fissures/ piles

Docusate- softens faeces

Mineral oils- lubrication

Fecal Softeners

Osmotic LaxativesPoorly absorbed solutes

Maintain an increased volume of fluid in GI tract, therefore accelerating transit time

Saline purgatives- Mg sulphate and Mg hydroxide used for bowel prep prior to procedure as rapidly acting

Lactulose- semi synthetic disaccharide (fructose and glucose) 2 poorly absorbed monosaccharaides (by colonic bacteria) fermentation yields lactic acid + acetic acid. Acts in 1-3 days and can be prescribed alongside opioids

Bulk LaxativesPolysaccharide polymers that are NOT broken

down by the normal process of digestion

Retain water in the GI lumen, softening and increasing fecal bulk and promote motility

Eg. Methylcellulose and plant gums such as bran, agar or ispaghula husk

Faster acting- 1-3 days

Good first choice for constipation and IBS

Stimulant laxatives- Senna + Bisacodyl

Contains a glycoside which passes unchanged into the colon

Bacteria act upon it to release free anthrancene derivatives which have a direct effect upon the myenteric plexus

Usually taken at night and takes around 8hrs to work

Short term use is safe but abuse melanosis coli and/or cathartic colon

Bisacodyl usually given as a suppository

Stimulates rectal mucosa mass movements and defecation in 15-30mins

What is diarrhoea?Frequent, watery, loose bowel movements involving increased GI motility and secretion and decreased absorption of water

What factors could cause diarrhoea?• Infectious agents• Toxins• Anxiety• Drugs

• Antibiotics• PPIs• Antidepressants

What are the 4 main types of diarrhoea?Motility-related diarrhoea

Osmotic diarrhoea

Inflammatory diarrhoea

Secretory diarrhoea

What are the main treatments for diarrhoea?Maintenance of fluid/ electrolyte balance

(ESP. Na+ and K+)

Anti-infective agents

Anti-diarrheal agents

Anti-motility agents

Eg. Immodium or diocalm

Opioids: codeine + loperamide

Loperamide has relatively selective action on GI tract – mu opioid receptors in the myenteric plexus

Increases tone and rhythmic contractions of colon whilst diminishing propulsive activity