Constipation

Aetiology: Contents moving slowly in the large intestine while drawing up more water absorbed from the faecal matter

Cause
  • Not including enough fibre (fruits and veg)
  • Not drinking enough liquid
  • Not enough exercise
  • Medication (opioid induced, antacids containing aluminium, antispasmodics, antidepressants, diuretics, iron supplements and antiepileptic medicines)
  • IBS
  • Pregnancy– hormonal changes and increased pressure on the abdomen
  • Ageing– The movement of large intestine may become slower
  • Excessive laxative use (August 2020 MHRA warning on overuse of laxatives and has made smaller pack sizes available for 2 short courses
  • Cancer; cancer in the intestines can cause diarrhoea and/or constipation normally accompanied by unintentional weight loss and blood or mucus in the stools
Symptoms 
  • Not passing stool as often as they
  • Feeling you can’t empty your bowels properly
  • Pain when defecating due to solid hard stools
  • Abdominal discomfort
  • Wind
  • Blood being passed in the stool
  • Stomach cramps
Red Flags
  • New or worsening constipation without adequate explanations
  • Blood in the stools
  • Weight loss
  • Nausea and vomiting.
  • This is to rule out colorectal cancer. Any reports of rectal bleeding with change in bowel habit should be questioned further and referral to the GP is usually warranted (unless haemorrhoids are suspected)
  • Symptoms that suggest faecal impaction should also be referred to the GP, as manual evacuation may be required.

New onset constipation especially in patients over 50 years of age, or accompanying symptoms such as:

  • Anaemia
  • Abdominal pain
  • Weight loss, or overt or occult blood in the stool should provoke urgent investigation because of the risk of malignancy or other serious bowel disorder.


Drug induced constipation

Drug induced constipation

  • Aluminium antacids
  • Antidepressants (phenelzine, amitriptylline)
  • Antiepileptics (carbamazepine)
  • Antihistamines (brompheniramine)
  • Antipsychotics (clozapine, quetiapine)
  • Antispasmodics (dicycloverine, hyoscine)
  • Calcium supplements
  • Diuretics (furosemide, indapamide)
  • Iron supplements
  • Opioids (codeine, buprenorphine, morphine)
  • Verapamil
Cautions
  • Cardiovascular disease — do not prescribe more than two sachets of full-strength macrogol compound oral powder in any one hour, and advise the person to discontinue if symptoms of fluid and electrolyte disturbance occur.
  • Lactose intolerance (lactulose) — may cause diarrhoea.
  • Ischaemic heart disease or arrhythmias (prucalopride).
  • Ischaemic colitis (macrogel).
  • Movicol is considered high in sodium, this should be taken into account for those people on a low salt diet.
  • Active Chrons or Ulcerative Colitis 


When not to prescribe laxatives

Do not prescribe laxatives if there is suspected:

  • Intestinal obstruction or perforation.
  • Paralytic ileus.
  • Colonic atony or faecal impaction (bulk-forming laxatives).
  • Toxic megacolon.


Opiod Induced Constipation

Recommended to use:

  • Osmotic laxative or docusate sodium to soften the stools and a stimulant laxative.
  • Naloxegol and methylnaltrexone bromide are both recommended for patients who have an inadequate response to other laxatives. In palliative care, methylnaltrexone bromide should be used as an adjunct to existing laxative therapy
  • Bulk-forming laxatives should be avoided.


Constipation in children 

First line: Laxatives (Macrogol is the preferred first-line laxative), dietary modifications, and behavioral interventions.

If response is inadequate: Add a stimulant laxative, or change to a stimulant laxative if the first-line therapy is not tolerated.

Lactulose or faecal softener if stool remains hard

Laxatives should be administered at a time that fits in with the child’s toilet routine.

Bulk Forming
Place in therapy:
Useful first-line choice in adults when it is difficult to get adequate dietary fibre; better tolerated than bran. They are of particular value in adults with small hard stools if fibre cannot be increased in the diet.

Drug action:
Swells in gut to increase faecal mass to stimulate peristalsis

Side Effects: flatulence, bloating, and cramping may be exacerbated

Pregnancy:
First choice during pregnancy

Breastfeeding:
First line

Chronic constipation: 

Start with bulk forming and first line in children. Acute constipation, use bulk forming laxative and if stools remain hard, add or switch to an osmotic laxative, soft but difficult to pass add a stimulant

Counselling: Maintain fluids to avoid gut obstruction and to not to take immediately before bed

Opioid Induced 
Constipation: Avoided in opioid induced constipation

Sterculia:
Not to be taken with other constipating drugs

Osmotic Laxatives:
Drug action:
Increase the amount of water in the large bowel, either by drawing fluid from the body into the bowel or by retaining the fluid they were administered with

Side effects: Discomfort, flatulence, cramps, nausea

Pregnancy:
Safe

Breastfeeding: Lactulose or a macrogol is safe

Note: Lactulose is a semi- synthetic disaccharide which is not absorbed from the gastro-intestinal tract it produces diarrhoea of low faecal pH, and discourages ammonia-producing organisms, therefore used in treating hepatic encephalopathy.

Lactulose: If used alone in opioid-induced constipation, it often needs to be given in large doses that cause bloating and colic

Chronic Constipation: Bulk forming is first- line but macrogol choice in osmotic laxative category. Add stimulant if no response

Macrogols: Difficult to drink in prescribed volumes, Idrloax no electrolytes and Movicol-Half contains half the dose and electrolytes of Movicol

Stimulant Laxatives

Drug action:
Increase intestinal motility

Side effects: 
Abdominal cramp; manufacturer advises they should be avoided in intestinal obstruction. Excessive use can cause hypokalaemia

Counselling:
Senna colours urine yellow brown. Usually taken in the evening to produce a bowel movement the following morning.

Pregnancy:
Bisacodyl and senna safe- avoid senna near term (can stimulate uterine contractions).

Breastfeeding: Bisacodyl or senna safe

Stimulant laxatives They more effective than bulk-forming laxatives but are more likely to cause side-effects (diarrhoea and abdominal discomfort), reducing patient compliance

Senna:
Licensed only for short-term use. Syrup is unpalatable.

Sodium picosulphate: Licensed only for short-term use.

Bisacodyl:
Licensed only for short-term use. No syrup available.

Co-danthramer and co-danthrusate:  Limited to constipation in terminally ill patients because of potential carcinogenicity (based on animal studies) and evidence of genotoxicity.

Stool Softeners

Drug Action: 
Increasing the amount of water and fat absorbed by the stool, making it softer and easier to pass.

Side effects: 
Diarrhea, abdominal cramps, nausea, skin rash or itching

Pregnancy:
Safe

Breastfeeding:
Safe

Docusate:
Acts both as a softening agent and a stimulant. May be a useful alternative for people who find it hard to increase their fluid intake.