Nausea vomiting diarrhoea Flashcards
DEscribe dopaineantgonists
MoA
Blocks D2 receptors inthe chemoreceptor trigger zone (CTZ)
At high doses is 5HT-3 blocker (may also block histamine and muscarinic receptors)
Prokinetic (increased gastric emptying) effects on upper GIT
Indications
Commonly used antiemetic class
Adverse effects
- can cause acute dystonias/Parkinsonism and tardive dyskinesia or extrapyramidal side effects
-
Contraindications
- avoid in PD (domperidone is a D2 antagonist, and prokinetic, that does NOT cross BBB and may be suitable in some PD patientes)
Describe constipation
- Difficult faecal evacuation as a result of hardness and infrequent movements
- Changes in bowel habit
- Regular movement are individualised to the patient
- Factors that contribute to constipation include:
- failure to respond to defaecation impulses
- sedentary lifestyle
- insufficient exercise
- impaired physical mobility
- change in routine, e.g. travel
- Chronic constipation can be a result of:
- lack of dietary fibre
- ↓ fluid intake
- Underlying disease states:
- tumours
- bowel obstruction
- diseases of liver, gallbladder or muscles
- Neurological disorders
- MS
- Parkinson’s disease
- pregnancy
- Adverse effect of many drugs
- The elderly have a higher risk of constipation
Describe prucalopride
A 5HT4receptor agonist that increases GI motility (prokinetic) used in chronic idiopathic constipation, when other regular laxatives are inadequate.
Onset of laxative effect generally occurs within the first few weeks (not fast acting!)
nOTE; the usual stepwise approach to treating functional constipation in adults is as follows: bulk forming, osmotic, stimulant, prokinetic
Describe opioid induced constipation
- Activation of mu receptors found in the intestinal tract lead to inhibition of peristalsis and are not affected by opioid tolerance.
-
Methylnaltexone is used to treat opioid-induced constipation
- Peripherally acting competitive mu opioid receptor antagonist. It blocks the constipating effects of opioids in the GIT but has limited ability to cross the blood–brain barrier, therefore does not antagonise their analgesic effects.
- Oxycodone (an opioid analgesic) is available as a co-formulation with naloxone (opioid antagonist) to inhibit opioid receptor binding in the GIT and reducing constipation.
Describe diarrhoea
Passage of liquid faeces occurring as a result of:
- ↓ absorption by the small and/or large intestine
- Osmotic diarrhoea:
- Accumulation of non-reabsorbable solutes
- Secretory diarrhoea:
- Excessive secretion in the small intestine and colon
- Causes
- Drugs:
- Lots of various medications
- antibiotics
- magnesium containing antacids and laxatives
- Infectious
- Drugs:
- Can be acute and self-limiting or chronic lasting 3-4 weeks or more
- Careful consideration as to the cause of diarrhoea needs to be considered before anti-diarrhoeal therapy is commenced.
- opioid
- eg codeine, loperimide, diphenoxylate
- Activate opioid mu receptors in the gut wall. Inhibit secretions and motility of smooth muscle cells (via inhibition of Ach release by enteric nervous system.
- adsorbent
- aluminium hydroxide, attapulgite, kaolin and pectin
- Coat the intestinal mucosa adsorbing bacteria/toxins causing diarrhoea.Less effective than opioids
- alpha 2 antagonist
- clonidine eg diabetic diarrhoea
- alpha-2 receptor activatioin on enterocytes increases fluid absorption and inhibits secretion as well as inhibiting GI motor activity by inhibiting Ach release
- belladonna alkaloids
- hyoscine and atropine
- anticholinergic effects
- bile salt binder
- cholestyramine
- Used in bile salt malabsorption (eg terminal ileal resection)
DEscribe lopearmiade
MoA’
Activates opioid receptors in the gut wall (no central effects)
- ↓ secretions and inhibit propulsive movements in the gut
- Slow the passage of intestinal contents
- Allow reabsorption of water & electrolytes
- ↓ stool frequency
Indications
Short term treatment - Diarrhoea
- Intestinal stoma (to reduce frequency and fluidity of motions)
Adverse effects
Abdominal pain and bloating, nausea, vomiting, constipation
Describe coedine
MoA’
Natural occurring opioid (a pro-drug of morphine - 10% is converted to morphine in the liver) .
Agonist at mu receptors in the GIT causing inhibition of peristalsis -> constipation
Does also work centrally and therefore can have opioid related side effects such as drowsiness and nausea.
DESCRIBe diphenoxylate
MoA’
- Inhibits intestinal propulsive motility
- Acts directly on mu (μ) opioid receptors on intestinal smooth muscle
- The addition of atropine acts as an anticholinergic and also to discourage abuse
Indications
Adverse effects
Abdominal pain, nausea, vomiting, constipation, rash, dizziness and drowsiness, anticholinergic side effects (due to atropine)
Describe H1 natags
Block histamine from activating the H1 receptor
Cause drowsiness - less commonly used in practice due to drowsiness
Indicated for postoperative nausea and vomiting, motion sickness and radiation-induced nausea and vomiting
eg promethazine cyclizine
DEscrbe seritinin
5HT receptors occure peripherally in the GIT on the vagus nerve and centrally in the vomiting centre and the CTZ
Useful in most causes of nausea and vomiting such as post-op, chemotherapy, etc
Commonly used antiemetic class
Side effects: Well tolerated, can prolong the QT interval
Describe muscarninc antagonsits
Competitively blocks acetylcholine receptor (M1) in vestibular and vomiting centre
Mostly used for motion sickness
Anticholinergic side effects - limits use in practice, but are used if abdominal cramps are problematic
hyoscine
Describe neurokiinin1 antagonsists
eg aprepitant)
Act on NK 1 receptors located through CNS and involved in pain and emetic pathways
Used to treat chemotherapy-induced nausea and vomiting (usually in combination with other agents)
Relatively new agents and place in therapy is evolving
Describe GCs and benzos
eg aprepitant)
Act on NK 1 receptors located through CNS and involved in pain and emetic pathways
Used to treat chemotherapy-induced nausea and vomiting (usually in combination with other agents)
Relatively new agents and place in therapy is evolving
Descrieb herbals
Cannabinoids:Complex mixture of agents usually reserved for palliative care scenarios.
Ginger - often used in nausea and vomiting during pregnancy and is likely to be helpful
