Pharmocology Flashcards
what drugs are used for acid suppression?
> antacids
h2-receptor antagonists
proton pump inhibitors
what drugs affect GI motility?
> anti-emetics
anti-muscarinics
anti-motility
what drugs are used in inflammatory bowel disease?
> aminosalicylates
corticosteroids
immunosuppressants
biologics
what drugs affect intestinal secretions?
> bile acid sequestrants
> ursodeoxycholic acid
what metals do antacids contain?
magnesium or aluminium
what is the action of antacids?
they neutralise gastric acid
what is the action of alginates?
they form a viscous gel that floats on the stomach contents reducing reflux
describe the action of H2-receptor antagonists
they block histamine (H2) receptor thereby reducing acid secretion
when are h2-receptors indicated?
in GORD or peptic ulcer disease
unless patient cannot use proton pump inhibitor do not use a lot of them
how are h2-receptor antagonists administered?
orally or intravenously
when are proton pump inhibitors indicated?
in GORD or peptic ulcer disease
how are proton pump inhibitors administered?
orally or intravenously
what is triple therapy for treatment of PU/DU associated with?
H. Pylori
what problems are associated with proton pump inhibitors?
> GI upset
predisposition to c. difficile infection
hypomagnesaemia
b12 deficiency
what agents increase gut motility and gastric emptying?
prokinetic agents
what is the mechanism of prokinetic agents?
it is not clear but involves parasympathetic control of smooth muscle and sphincter tone
what is the action of domperidone?
it acts by blocking dopamine receptors which inhibit post synaptic cholinergic neurones
what drugs work on the chemoreceptor trigger zone to stop vomiting?
> dopamine antagonists
5HT3 antagonists
cannabinoids
what drugs act on the pharynx and GIT to stop vomiting?
> 5HT3 antagonists
> dopamine antagonists
what drug acts on the vestibular nuclei to stop vomiting?
anti-histamines
what drugs act on the vomiting centre in the medulla to stop vomiting?
> anti-muscarinics
> anti-histamines
what is the mechanism of action of loperamide?
it acts on the opiate receptors in the GI tract to decrease ACh release. this decreases smooth muscle contraction and increases anal sphincter tone causing a decrease in motility.
why does loperamide have few central opiate effects?
it is not well absorbed across the blood-brain barrier
by what three mechanisms do antispasmoids reduce symptoms of IBS and renal colic?
> anti-cholinergic muscarinic antagonists (inhibit smooth muscle contraction in gut wall)
direct smooth muscle relaxants
calcium-channel blockers reduce calcium required for smooth muscle contraction
what are the 4 types of laxatives?
> bulk
osmotic
stimulant
softeners
what issues can there be with laxatives?
> obstruction (lead to perforation)
route of administration (oral or rectal)
other measures as oral laxative will not work without adequate fluid intake
misuse
what is the action of aminosalicylates?
anti-inflammatory
how are aminosalicylates administered?
orally or rectally
when should you avoid prescribing aminosalicylates?
> in patients allergic to salicylates (as they are chemically related)
when should you use caution in using aminosalicylates?
in renal impairment
what are the adverse effects associated with aminosalicylates?
> GI upset
blood dyscrasias
renal impairment
how are corticosteroids administered?
orally, IV or rectally
what are contraindications for use of corticosteroids for IBD?
> osteoporosis
> cushingoid features including weight gain, DM, HT
what concerns are there with using corticosteroids for IBD?
> there is increased susceptibility to infection
> addisonian crisis, with abrupt withdrawal (hypertensive, dehydrated)
what is the action of immunosuppressants in IBD?
they prevent to formation of purines required for DNA synthesis so reduces immune cell proliferation
what are the adverse effects associated with use of immunosupressants in IBD?
> bone marrow suppression
azathioprine hypersensitivity
organ damage
numerous drug interactions
what is required when using immunosuppressant’s in IBD?
specialist use and close monitoring
what is infliximab?
a biologic, antiTNF(alpha)antibody.
mouse human chimeric antibody to TNF-alpha
what do biologics prevent?
action of TNF alpha, key cytokine in inflammatory response
what are the cautions/contraindications of infliximab?
> current TB (or other serious infection)
multiple sclerosis
pregnancy/breast feeding
what are the adverse effects associated with infliximab?
> risk of infection (TB) > infusion reaction (fever, itch) > anaemia, thrombocytopenia, neutropenia > demyelination > malignancy
name some biologics other than infliximab
> certolizumab
adalimumab
golimumab
vedolizumab
what is certolizumab?
fab fragment of humanized anti-TNF alpha monoclonal antibody
what is adalimumab?
humanized recombinant antibody to TNF
what is natalizumab?
ant-integrin monoclonal antibody
what is the action vedolizumab?
it binds to integrin alpha4beta7 (peyers patch adhesion molecule)
what is the action of cholestyramine?
it reduces bile salts by binding with them in the gut so they are excreted as insoluble complex
what may cholestyramine affect?
> absorption of other drugs
> fat soluble vitamin absorption (may decrease vitamin k levels affecting warfarin and clotting)
what is ursodeoxycholic acid used to treat?
> gallstones
> primary biliary chirrhosis
what is the action of ursodeoxycholic acid?
it inhibits enzymes involved in the formation of cholesterol altering the amount in bile and slowly dissolving non-calcifies stones
what problems may there be with the ADME of GI pharmacology?
> GI/liver diseases can affect the processes of the drug ADME
GI symptoms also necessitate a change in route of administration
what may affect the absorption of a drug?
> pH
gut length
transit time
what may affect the distribution of a drug?
> low albumin (decreased binding leads to increased free drug concentration)
what may effect the metabolism of a drug?
> liver enzymes
increased gut bacteria
gut wall metabolism
liver blood flow
what may effect the excretion of a drug?
> biliary excretion
what GI adverse effects can there be with medication?
> diarrhoea/constipation
GI bleeding/ulceration
changes to gut bacteria
drug induced liver injury
what is 25% of all drug induced diarrhoea due to?
antimicrobials
what are the effects of changes to gut bacteria?
> loss of OCP activity
reduced vitamin K absorption (increased prothrombin time)
overgrowth of pathogenic bacteria
what type of ADR is intrinsic hepatotoxicity?
type a as it is predictable, dose dependent and acute
what type of ADR is idiosyncratic hepatotoxicity?
type b as it is unpredictable, not dose dependent and can occur at anytime
what are the effects of idiosyncratic hepatotoxicity?
they can range from asymptomatic increase in LFTs to fulminant liver failure and death
what are the risk factors of hepatotoxicity?
> elderly > female > alcohol > genetic factors > malnourishment
what classification is used when judging the severity of liver disease?
child-pugh classification
what are the groups in the child-pugh classification?
A= <7 B= 7-9 C= >9
what things are scored in the child-pugh classification of liver disease?
> bilirubin > albumin > PT (prolonged) > encephalopathy > ascites
when prescribing for liver disease what should you take care of/avoid?
> drugs that can be toxic due to changes in pharmacokinetics
drugs which are hepatotoxic
drugs which may worsen the non-liver aspects of liver disease
what specific drugs should you avoid in liver disease?
> warfarin (clotting factors already low)
aspirin/NSAIDs (increases bleeding time, can worsen ascites)
opiates/ benzodiazepines (may precipitate encephalopathy)
