Laxatives

Clinical Uses

Laxatives may be required for the following conditions:

1. In cardio-vascular disease

2. In patients with hemorrhoids

3. Following surgery

4. To clear the gut before surgery or for diagnosis

5. Hormonal change in pregnancy

6. Drug induced

Preparations available of Laxatives

A. Bulk Laxatives

1. Most of them are prepared from natural substances, such as wheat, in form of granules or powder intended to be mixed with fluid before taking

2. They absorb fluid in the gut, swell and increase faecal mass, which exert pressure to the gut wall and stimulates bowel movement

3. The laxative effect will take 3 days to develop

4. Increase fluid intake in order to avoid faecal impaction and obstruction in the oesophagus

5. Bulk laxatives are recommended in pregnancy and cannot have enough fiber intakes

Preparation

Ispahula husk (Fybogel, Isogel)

Psyllium (Metamucil)

Sterculia (Normacol)

Methylcellulose (Celevac)

B. Stimulant Laxatives

1. Stimulate nerve endings in the gut wall and increase intestinal movement

2. They work within 6-12 hours

3. Stimulant laxatives should not be used for more than one week

4. Produce gripping pain

5. Can cause tolerance, smooth muscle atony in the colon and potassium loss

Preparation

Senna glycosides (e.g. Senokot tablets, granules)

Anthraquinones are the active compound liberated into the colon by gut and increase intestinal movement

Aloes, Cascara and Rhubarb belongs to the anthraquinone group and has similar properties

Bisacodyl (Dulcolax tablets, suppositories)

Often used for evacuation of colon before endoscopies or after surgical operation

Taken orally it acts within 6-10 hours

Given as a suppository, the effect usually occurs with one hour

Dulcolax tablets are enteric coated; antacids should be avoided within one hour of administration

C. Osmotic Laxatives

Osmotic laxatives act by retaining fluid in the gut by osmosis

The increase pressure in the gut then stimulates bowel movement

Produce a rapid bowel evacuation within a few hours

Preparation

1. Magnesium Salt (Saline Purgatives)

Magnesium sulphate (Epsom salt)

Should not be used regularly, especially in patients with renal impairment, because it may be absorbed causing unconsciousness

It should also be used with care in the elderly and patients with cardiac problems

Magnesium hydroxide (Milk of Magnesia)

Commonly abused but is safe for occasional use

Golytely

Polythene glycol 3350 (an emulsifying agent) 118 g + Potassium chloride 1.5 g + Sodium chloride 2.9 g + Sodium bicarbonate 3.36 g + Sodium sulphate 11.36 g = [137 g per packet]

Dissolve whole pack in 2 liters of water and drink at the rate of 1 liter/hour

This preparation is used for whole bowel irrigation in preparation of GI examination, X-ray procedure and colonic surgery

Fleet Enema

Sodium bi-phosphate 19 g + Sodium phosphate 7 g = [in bottle of 4.5 fl.oz]

This is a saline laxative with rapid onset of action

It is used for constipation and bowel cleansing before rectal examination

2. Lactulose (Duphalac)

3.

Non-absorbable disaccharide, which retains water in the bowel by an osmotic action

Gut bacteria degrade Lactulose to acetic and lactic acids, which stimulate colon motility

It has a slow onset of action of 1-2 days, but is safe and effective for children and the elderly

Usual dose: 15ml bd for 3 days, For hepatic encephalopathy 30-50 ml tds

Glycerin suppositories/ Glycerin bulb enema

Have both osmotic and irritant effects and usually act within an hour

May cause rectal discomfort

Moistening the suppository before use will make insertion easier

D. Faecal Softeners

Docusate Sodium/ Dioctyl Sodium Sulphosuccinate (Colace, Softon) 1-2 Caps daily

Emulsifying agents, which reduce the surface tension of hard stool and allow water to penetrate into the faecal mass and soften the faeces

They work rather slowly (in 1-2 days), but are safe for the elderly and those who had a stroke or myocardial infarction

Useful as an adjunct to stimulant laxatives in the treatment of Opioid-induced constipation

E. Lubricant Laxatives

Liquid Paraffin, Agarol

Liquid paraffin works by coating and softening the faeces and prevents further absorption of water into the colon

Long-term use can result in impaired absorption of fat-soluble vitamins and leakage of liquid paraffin through the anus may occur

Choice of Laxatives

Constipation in Children

Change in diet and emotional causes

A single glycerin suppository and dietary advice

Constipation in Pregnancy

Hormonal changes and oral iron

In take of plenty of high fiber foods and fluids can help

Bulk laxatives are preferred when necessary

Constipation in the Elderly

Less physically active and poor natural teeth

Bulk laxative is recommended

Laxative Abuse

1. Those with chronic constipation get into the vicious cycle by using stimulant laxatives repeatedly

2. This damages the nerve plexus in the colon leading to smooth muscle atony in the colon

3. Prolonged use of laxatives to control weight may form a habit and may result from water and electrolyte loss

4. Especially sodium and potassium leading to postural hypotension (Orthostatic hypotension) general weakness and arterial fibrillation