Constipation Flashcards
what factors need urgent investigation because of risk of malignancy or other serious bowel disorder?
New onset constipation, especially in patients >50 years of age, or anemia, abdominal pain, weight loss, or overt or occult blood in stool
Laxative abuse leads to
hypokalaemia
Bulk forming laxatives
e.g. bran, ispaghula husk, methylcellulose, sterculia. → particular value in adults with small hard stools if fibre cannot be increased in diet.
→ Onset of action = 72 hours
SEs: flatulence, bloating, cramping
!! Adequate fluid intake must be maintained to avoid intestinal obstruction !!
AVOID IN OPIOID INDUCED CONSTIPATION
Stimulant Laxative
e.g. bisacodyl, sodium picosulfate, senna, co-danthramer, co-danthrusate.
→ increase intestinal motility
→ onset : 6-12h
→ cause abdominal cramp; manufacturer advises avoided in intestinal obstruction
→ co-danthramer & co-danthrusate = constipation in terminally ill pt as of potential carcinogenicity & evidence of genotoxicity.
→ Docusate sodium = also faecal softener.
→ Glycerol suppositories act as lubricant + rectal stimulant
→ Senna discolours urine + hypokalaemia
excessive stimulant laxative used leads
hyPOkalaemia, diarrhoea, lazy bowel
Stimulant counselling points
~ take @night to pass stool in morning
~ moisten suppositories with water before use
Faecal softners
act by decreasing surface tension and increasing penetration of intestinal fluid into faecal mass.
e.g. Docusate sodium, glycerol suppositories
Enemas with arachis oil (ground-nut oil, peanut oil) lubricate & soften impacted faeces & promote bowel movement.
Liquid paraffin also been used as lubricant for passage of stools but manufacturer advises used with caution as anal seepage & risks of granulomatous disease of GIT or of lipoid pneumonia on aspiration
Osmotic laxatives
increase water absorption in large bowel
→ Onset: 2-3 days, 48h for lactulose
e.g. Lactulose …useful in tx of hepatic encephalopathy, Macrogols
SEs: flatulence, cramps, N, discomfort
Short term constipation if dietary measure ineffective tx
- bulk-forming laxative, ensuring adequate fluid intake.
If stools remain hard, add or switch to osmotic laxative.
If stools soft but difficult to pass or person complains of inadequate emptying, stimulant laxative added
Opioid induced constipation tx
- osmotic (or docusate sodium) + stimulant laxative
!! Bulk-forming laxatives avoided !!
→ Naloxegol = tx of opioid-induced constipation when response to other laxatives inadequate.
Methylnaltrexone licensed for tx of opioid-induced constipation when response to other laxatives inadequate
Faceal impaction tx
depends on stool consistency.
In hard stools
→ high dose of oral macrogol
In soft stools/hard stools after few days → macrogol, oral stimulant laxative started/added to previous tx. If response to oral laxatives inadequate, for soft stools = rectal bisacodyl, and for hard stools rectal administration of glycerol alone, or glycerol + bisacodyl. Alternatively, enema of docusate sodium or sodium citrate
If response still insufficient, sodium acid phosphate with sodium phosphate or arachis oil retention enema may be necessary. For hard faeces helpful to give enema of arachis oil overnight before giving enema of sodium acid phosphate with sodium phosphate or sodium citrate the following day. Enemas may need to be repeated several times to clear hard impacted faeces
Chronic constipation tx
- bulk-forming laxative
- If stools remain hard, add or change to osmotic laxative (Macrogol)
- If response inadequate, stimulant laxative.
Pregnancy/BF and constipation
1st line: dietary & lifestyle changes (fibre supplements form of bran or wheat likely to help)
2nd choice: bulk-forming
3rd choice: osmotic (lactulose)
4th choice: Bisacodyl / senna if stimulant effect is necessary BUT senna avoided near term or if history of unstable pregnancy.
Docusate & glycerol suppositories also used.
if at least 2 laxatives (different classes) tried at highest tolerable dose for at least 6m
~ Prucalopride (women only) ~ if not effective after 4 weeks, re-examine
~ Lubiprostone
Constipation in children (not faecally impacted)
1st line = Macrogol
then add stimulant
then add lactulose or faecal softener if stools remains hard
