Drug information - Laxatives

LAXATIVES

Laxatives are a class of drugs used in the treatment of Constipation. Laxatives and Purgatives are known as Cathartics as they are known to cause Catharsis. Catharsis is the evacuation of the bowel and is usually done before the diagnostic procedures or surgeries of the bowel.

Constipation is the functional impairment in the inherent capacity of the colon to produce normal stools at regular intervals. It is usually associated with difficulty in emptying the bowels and hard faeces. 

Causes: Constipation is mainly caused due to decrease in colonic motility due to - ageing, emotions, low bulk diet, low liquid intake, spastic colon, chronic amoebiasis, or due to drugs. The drugs that cause this effect are Diuretics, anti-diarrhoeal, Anticholinergics, MAOI (Mono Amine Oxidase Inhibitors), Opioids, Tricyclic anti-depressants, Analgesics, and Antacids.

Laxatives are further classified into - 

1. Bulk-forming agents - 

This includes - Dietary fibre bran, Psyllium (Plantago), Ispaghula, and Methylcellulose.

2. Stool softener - 

This includes - Docusates (DOSS), Liquid Paraffin

3. Stimulant laxatives - 

This includes - 

1. Diphenylmethanes - Phenolphthalein, Bisacodyl, Sodium picosulfate

2. Anthraquinone laxatives - Senna, Cascara Sagrada

3. 5 HT 4 agonist - Prucalopride

4. Fixed oil - Castor oil

     4) Osmotic laxatives - 

            This includes - Magnesium sulfate, Magnesium hydroxide, Sodium sulfate, Sodium phosphate, Sodium potassium tartarate, Lactulose

Let's understand the Pharmacology of Laxatives. 

1. Methylcellulose - 

It is available in powder form. 

Dose - 2 grams of powder in 250ml of water. 

Route - Orally

Frequency - OD or TID based on patient need

MOA - It is a bulk-forming agent. It absorbs water in the intestine, swells and increases the water content of the faeces, thereby softening it and facilitating the passage of stools.

ADRs - Flatulence, Impaction, Excessive bowel activity

Contraindications - Hypersensitivity, bowel obstruction, dysphagia, appendicitis, rectal bleeding

DI’S - No major drug interactions

Pregnancy and lactation - No specific data available. Can be used.

Patient Education and Counselling - The patient must be educated to mix the dry powder with water before consuming. Bulk-forming laxatives should not be taken in dry form as they can cause abdominal cramps.

2. Docusate (Dioctyl sodium sulfosuccinate - DOSS) -

            It is available in tablet, capsule, syrup and enema form

Dose - 100-400mg/day, acta in 1-3 days

Route - Oral, Rectal in form of an enema

Frequency - OD, TID based on patient need

MOA - It softens the stools by net water accumulation in the lumen by acting on the intestinal mucosa

ADRs - Abdominal cramps, Diarrhoea, excessive bowel activity, intestinal obstruction, throat irritation

Contraindications - Hypersensitivity, Intestinal obstruction, Nausea, Vomiting, Concomitant use of Mineral oil

D.I’s - Enhances G.I absorption of drugs. Concurrent administration with mineral oil or liquid paraffin should be avoided, as it may cause electrolyte imbalance.

Pregnancy - To be used with caution. Only if the benefits outweigh the risk.

Lactation - No specific data. Can be used

Patient Education and Counselling-

Counsel patients on the method of administration of the drugs- both in oral form and enema. 

Counsel patients to avoid excess use as it may lead to dependence and cause electrolyte imbalance. 

Counsel patients on the importance of fibre rich diet, optimum liquid intake and regular exercises to prevent constipation.

3. Bisacodyl - 

5-15mg- Orally- Once daily.

Maximum dose 30mg OD.

MOA - Irritates the smooth muscles, thereby increasing peristalsis. Also increases intestinal fluid accumulation and laxation by altering water and electrolyte secretion.

ADRs - Abdominal cramps, fluid and electrolyte imbalance, excessive diarrhoea, vertigo.

Contraindications - Hypersensitivity, G.I Obstruction, appendicitis, rectal bleeding

D.I’s - Concurrent use with sodium sulfate/potassium sulfate/magnesium sulfate/potassium chloride/ PEG - should be avoided as it increases the toxicity of bisacodyl and increases the risk of mucosal ulceration or ischemic colitis.

Use with caution deflazacort and dichlorphenamide as both decrease serum potassium.

Pregnancy - Short-term use if safe, Avoid long-term use.

Lactation - Use with caution if the benefits outweigh the risk.

Patient Education and Counselling-

Counsel patients regarding medication use. The tablet should be swallowed and not chewed. It should not be used within 1 hour of taking antacid or milk. Not be used for duration > 1 week.

Avoid chronic use.

Avoid administration in patients with Gastroenteritis.

4. Senna - 

Dose - 15mg OD. Not to exceed 70-100mg/day

Route - Oral

MOA -It stimulates the intestinal mucosa. Thereby increasing peristalsis and facilitating the passage of stools.

ADRs - Abdominal pain, diarrhoea, electrolyte abnormalities - hypokalemia, nephritis, yellow-brown urine discolouration

Contraindications - Hypersensitivity, G.I obstruction, appendicitis, rectal bleeding, Crohn’s disease

D.I’s - Concurrent use with sodium sulfate/potassium sulfate/magnesium sulfate/potassium chloride/ PEG - should be avoided as it increases the toxicity of Senna and increases the risk of mucosal ulceration or ischemic colitis.

Use with caution deflazacort and dichlorphenamide as both decrease serum potassium.

Pregnancy - Use with caution

Lactation -Can be used

Patient Education and Counselling-

Counsel patients not to self-medicate on Senna for > 1 week. As it leads to electrolyte abnormalities.

Not recommended in patients experiencing a sudden change in bowel movements lasting > 2 weeks e.g - stomach pain, nausea, vomiting. 

5. Prucalopride - 

2mg - Oral -OD

MOA - It is a 5-HT4 receptor agonist. Causes G.I Prokinetic action that stimulates colonic peristalsis, thereby increasing bowel activity.

ADRs - Hypersensitivity, urticaria, psychiatric disorders

Contraindications - Hypersensitivity, G, I Perforation

D.I’s - No drug interactions

Pregnancy and lactation - no sufficient data

Patient Education and Counselling- Counsel patients about the adverse effect- Psychiatric disorders. Counsel them to monitor for symptoms and report immediately to HCP in case of occurrence of any such symptom.

6. Castor oil - 

15 - 60ml Oral OD 

MOA - It stimulates the intestinal mucosa. Thereby increasing peristalsis and facilitating the passage of stools.

ADRs - Diarrhea, cramps, electrolyte imbalance, dizziness

Contraindications - Hypersensitivity, G.I obstruction, Ulcerative colitis

D.I’s - No drug interactions

Pregnancy - Avoid use in pregnancy as it can induce premature labour

Lactation - Can be used

Patient Education and Counselling- Counsel patients on the administration of castor oil.

Counsel patients to avoid use in pregnancy as it can induce premature labour

7. Magnesium hydroxide - 

It is commonly known as Milk of Magnesia.

Dose - 30-60ml/day - H/S

MOA - Promotes osmotic retention of fluid which distends the colon with increased peristaltic activity and stimulates bowel evacuation.

ADRs - Abdominal cramps, diarrhoea, electrolyte imbalance

Contraindications - Renal failure, Myocardial damage, Existing electrolyte abnormality, Intestinal obstruction

D.I’s - Decreases levels of eltrombopag by inhibition of G.I absorption. Maintain a gap of at least 4 hours. 

Pregnancy and Lactation - Can be used

Patient Education and Counselling-

Counsel patients to avoid use in case of renal insufficiency, existing electrolyte abnormalities, or undiagnosed abdominal pain.