Laxatives Flashcards
Laxative license in IBS
Linaclotide
Laxative first line in preg if dietary and lifestyle aren’t sufficient
Bulk forming - eg ispagula husk
Useful definition of constipation
Passage of hard stools less frequently that the patient’s own normal pattern
What electrolyte imbalance can result from laxative abuse
Hypokalaemia
The 4 main classes of laxatives
Bulk forming
Softening
Stimulant
Osmotic
Counselling for bulk forming laxatives
Adequate fluid intake must be maintained to avoid intestinal obstruction
What is an effective bulk forming preparation that I can’t find in the BNF?
Unprocessed wheat bran taken with food or fruit juice
What type of laxative is ispagula
Bulk forming
What type of laxative is methycellulose
Bulk forming and faecal softener
Name some bulk forming laxatives
Ispagula
Methycellulose
Stercula
Powerful laxatives like cascara and castor oil are obsolete but what sort of laxatives are they
Stimulant
What sort of laxative is docusate
Stimulant and softener
What sort of laxative is Senna
Stimulant
What sort of laxative is bisocodyl
Stimulant
What type of laxative is picosulfate
Stimulant
What sort of laxatives are co-danthramer and co-danthrusate
When can we use them
Stimulant
Palliative care - carcinogenic and genotoxic
What is the actin of glycerol suppositories
Lubricant and mild irritant ( in the stimulant section )
Disadvantage of stimulant laxatives
When to avoid
Often cause abdocramp
Avoid in obstruction
What can excessive use of stimulant laxatives lead to (2)
Diarrhoea and hypokalaemia
Why should we avoid unstandardised preparations of cascara, frangula, rhubarb and Senna?
Action is unpredictable
Why should we avoid aloes, jalap, colocyth
DRASTIC PURGATIVE ACTION
Parasympathomemeitcs are rarely used for their GI action as stimulants… Some examples of these include
Bethanechol
Neostigmine
Pyridostigmine
Softener are useful in what conditions according to the BNF
Haemorrhoids
Anal fissure
Liquid paraffin is what sort of laxative and what is the disadvantage
Softening
Leakageeeeeeeee
how do osmotic laxatives work?
increase the amount of water in the large bowel by drawing in fluid or retaining the fluid they were administered with
lactulose is what sort of laxative
what is it also used for? how does this work
osmotic - synthetic disacharide that is not absorbed from the GI - producing osmotic diarrhoea of low faecal pH thus discouraging ammonia producing organisms (treat hepatic encephalopathy)
macrogols are what sort of laxative
osmotic
what is the disadvantage of osmotic laxatives
dehydration - giving with fluid my reduce this
why should sodium salts be avoided as a laxative?
what is the mode of action here anyway?
sodium and water retention (osmotic laxative)
what type of laxative is magnesium salts
when is this used?
osmotic - often abused but ok for occasional use
phosphate enemas are what sort of laxative?
when are they used?
osmotic
surgery
what is licaclotide mode of action
what do we treat with it?
guanylate cyclase C receptor agonist that is used for IBS associated with constipation
it increases intestinal fluid secretion and transit and decreases viceral pain
(it’s metabolised in the GI and therefore virtually undetectable in the plasma)
what is lubipristone for?
mode of action?
chloride channel activator
idiopathic constipation that doesn’t respond adequately to lifestlye chages
what is prucalopride for?
mode of action?
treatment of chronic constipation in woment where other laxatives have failed
selective seritonin 5HT4 receptor agnonist with prokinetic properties
steps for constipation treatment in preg
-dietary and lifestyle
1st - bulk forming e.g. ispagula
2nd - osmotic e.g. lactulose
3rd - stimulant e.g. bisocodyl/ senna
how many days without passing stools should be a concern in children
3
should you sell laxatives for children
no - should be managed by a specilist
in infants what home type remedy could you use for constipation?
increased intake of fluids - particularly juice containing sorbitol (prune, pear or apple) may be sufficient
what laxatives are suitable for infants under 1 year
lactulose
oral prep containing macrogols or glycerol supositories can be used for faecal impaction
what is the treatment of constipation for children over 1 year
review of diet then macrogol then lactulose then stimulant
treatment of faecal impaction may initially …
increase symptoms of soiling and abdo pain
use macrogols and if this doesnt work in two weeks use a stumulant
when in the day should ispagula husk be had
not before bed
with plenty of fluid
how should methycellulose be taken when being used for ostomy control
avoid fluid intake for 30 mins before admin
what is a selective opioid antagonist used for opiod induced constipation
methylnaltrexone bromide (subcutaneous)
how long does lactulose take to act
about 48 hours
`codanthomer cautions
avoid prolonged exposure to skin
only for palliative care
what colour can codanthromer change your urine
red
senna is licensed from what age
2 years
what time of day is senna usually taken
at night
when in the day should sterculia be taken
NOT before going to bed - preparations that swell in contact with water shouldnt be then then
how does loperamide work?
who is it suitable for
opioid receptors in the gut but doesnt cross the BBB
antimotility
suitable for adults ONLY
why dont we use antibiotics for diahorreah in the UK
usually a viral cuase
what antibiotic might be given for prophylaxis of travelers diarrhoea - but prophylaxis is not usually recommended
cipro
when can bulk forming laxative be used for diarrhoea?
ispagula etc are used for diarrhoea associated with diverticuar disease
how does racecadotril work?
used for dihorreah, inhibits the breakdown of endogenous opioids thus increasing opioid stimulation in the GI
age at which you can sell loperamide OTC
18
