1.6.4 Osmotic laxatives

NHS England (NHSE) has published new prescribing guidance for various common conditions for which over-the-counter (OTC) items should not be routinely prescribed in primary care (quick reference guide). One of these conditions is infrequent constipation.

Many laxatives are cheap to buy and are readily available OTC along with advice from pharmacies. Some self-care medicines are available from shops and supermarkets. Please click here for further information, exceptions, and a patient leaflet.

Macrogol compound

Indications and Dose

Notes

  1. Time to effect: 2-3 days
  2. Each sachet should be dissolved in 125ml water
  3. May cause electrolyte disturbances and some patients find it difficult to drink the prescribed volume. Caution in elderly and fluid restricted patients
  4. Courses should not normally exceed 2 weeks
  5. Paediatric sachets are unlicensed for faecal impaction in children under 5 and for chronic constipation in children under 2 years of age
  6. Where a preferred brand is recommended for a particular presentation, prescribing by brand helps ensure cost-efficient use of local NHS resources (see preferred brand link above)
Lactulose
  • Solution (£2.61 = 500ml)

Indications and dose

  • Constipation in adults
    • Initially 15 mL twice daily, adjusted according to response
  • Constipation in children
    • 1 – 11 months: 2.5 mL twice daily, adjusted according to response.
    • 1 - 4 years: 2.5–10 mL twice daily, adjusted according to response
    • 5 - 17 years: 5–20 mL twice daily, adjusted according to response
  • Hepatic encephalopathy
    • Adult: Adjusted according to response to 30–50 mL 3 times a day, subsequently adjusted to produce 2–3 soft stools per day.

Notes

  1. Lactulose takes up to 48 hours to work therefore, should be taken regularly rather than "when required"
  2. Some patients find it unpleasant to take and compliance may be a problem.
  3. Its main clinical benefit is in the management of hepatic encephalopathy.
  4. Fluid needs to be increased whilst taking lactulose
  5. Avoid lactulose in patients with IBS as it may increase gas production and therefore exacerbate symptoms
Phosphate (rectal)

Indication and dose

  • Relief of constipation
    • The contents of one single dose enema
  • Perioperative use
    • The contents of one single dose enema

Notes

  1. Time to effect: 5 minutes
  2. Useful to remove hard, impacted stools.
  3. Correct administration important to prevent damage to rectal mucosa.
  4. Long tube phosphate enemas are licensed for self-administration. The longer tube is to allow easier self-administration not to allow enemas to be given higher in the rectum.
  5. Licensed for occasional use only.
  6. Use of phosphate enemas are contraindicated in people who have signs of dehydration or significant renal impairment, as there is an increased risk of hypernatraemia, hyperphosphataemia, hypocalcaemia, and hypokalaemia.
  7. Risk of rectal gangrene in people who are systemically unwell with a history of haemorrhoids.
  8. Contra-indications acute gastro-intestinal conditions (including gastro-intestinal obstruction, inflammatory bowel disease, and conditions associated with increased colonic absorption)
  9. Conditions pre-disposing the patient to retention of the enema can make the use of the product hazardous
  10. Where a preferred brand is recommended for a particular presentation, prescribing by brand helps ensure cost-efficient use of local NHS resources (see preferred brand link above)
Sodium citrate
  • Micro-enema 450mg/5ml (£0.43 = 5ml enema)

Indication and dose

Notes

  1. Time to effect: 5-15 minutes
  2. Smaller volume than a phosphate enema
  3. Useful to remove hard, impacted stools
  4. Licensed for occasional use only.
  5. Correct administration important to prevent damage to rectal mucosa
  6. Use with caution in the elderly or people at risk of sodium and water retention.

Different brands may have different licensed use and dosage recommendations – refer to SPC of individual brands.

 

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