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

• Oral powder, sachets (click here for preferred brand)
• Paediatric oral powder, sachets (click here for preferred brand)

Indications and Dose

• Acute obstructed and faecal impaction in adults
  
  • Up to 8 full strength sachets daily, all of which should be consumed within a 6-hour period
• Chronic constipation in adults
  
  • 1–3 full strength sachets daily in divided doses usually for up to 2 weeks; maintenance 1–2 sachets daily
• Opioid induced constipation in adults and Acute non-obstructed constipation in adults
  
  • Usually 1 full strength sachet once or twice daily
• Faecal impaction in children
  
  • Child 1 - 11 months: ½ -1 sachet daily (unlicensed use)
  • 1 – 4 years: 2 sachets on first day, then 4 sachets daily for 2 days, then 6 sachets daily for 2 days, then 8 sachets daily (unlicensed use)
  • 5 – 11 years: 4 sachets on the first day, then increased in steps of 2 sachets daily to a maximum of 12 sachets daily
• Chronic constipation in children
  
  • Child 1 - 11 months: ½ -1 sachet daily (unlicensed use)
  • 1 – 6 years: 1 sachet daily, adjust dose to produce regular soft stool (maximum 4 sachets daily) (unlicensed in children under 2 years of age)
  • 7 – 11 years: 2 sachets daily, adjust dose to produce regular soft stool (maximum 4 sachets daily)

Notes

1. Time to effect: 2-3 days
2. Each sachet should be dissolved in 125 ml 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 years of age and for chronic constipation in children under 2 years of age
6. MHRA Drug Safety Update (April 2021): Polyethylene glycol (PEG) laxatives and starch-based thickeners: potential interactive effect when mixed, leading to an increased risk of aspiration
   1. Addition of a PEG laxative to a liquid that has been thickened with a starch-based thickener may counteract the thickening action and result in a thin watery liquid. Avoid directly mixing together PEG laxatives and starch-based thickeners
7. 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

• Oral solution 3.1-3.7g in 5ml (£3.02 = 500ml)

Indications and dose

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

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)

• Enema 128ml (standard tube £27.93 = per enema; long tube £41.29 = per enema)

Indication and dose

• Relief of constipation
  • 128ml single dose
• Perioperative use
  • 128ml single dose

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. Licensed for occasional use only
5. 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
6. Risk of rectal gangrene in people who are systemically unwell with a history of haemorrhoids
7. Contra-indications acute gastro-intestinal conditions (including gastro-intestinal obstruction, inflammatory bowel disease, and conditions associated with increased colonic absorption)
8. Conditions pre-disposing the patient to retention of the enema can make the use of the product hazardous

Sodium citrate

• Micro-enema 450mg in 5ml (£0.43 = 5ml enema)

Indication and dose

• Constipation in adults and Constipation in children
  • 5ml single 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

Magnesium hydroxide

• Oral suspension 7.45-8.35% (£4.20 = 200ml)

Indication

• Relief of constipation in adults

Dose

• 30-45ml at bedtime mixed with water