Alimentary pharmacology Flashcards
what main drug types are used for acid suppression and give an example of a drug for each.
H2 receptor antagonists e.g. Ranitidine
alginates e.g. Gaviscon
Proton pump inhibitors e.g. Omeprazole
Antacids e.g. Mallox
how does gaviscon treat reflux?
it forms a viscous gel that floats on the stomach contents and reduces reflux
how does H2 receptor antagonists rescue acid production?
blocks histamine receptor therefore reducing acid secretion
how does PPI’s reduce acid secretion?
block the proton pump
how does antacids treat heart burn or reflux?
they neutralise the acid
what are some of the problems associated with a PPI such as omeprazole?
GI upset
Predisposition to clostridium difficile
Hypomagnesaemia
B12 deficiency
what are the 2 main drugs which affect biliary secretions?
cholestyramine
ursodeoxycholic acid
how does cholestyramine work?
what is the problem with this drug?
reduces bile salts by binding with them in the gut and excreting them as insoluble complex’s
problem - may affect absorption of fat soluble vitamins such as vitamin K
how does ursodeoxycholic acid work?
inhibits the enzyme involved in formation of cholesterol
this alters the amount of cholesterol in bile and slowly dissolves non calcified stones
what is the main drug which is used in the treatment of gallstones?
ursodeoxycholic acid
what are the main conditions which ursodeoxycholic acid treat?
gallstones
primary biliary cirrhosis
what are the different drug types which affect gut motility?
give an example for each of these.
pro kinetics e.g. domperidone
anti-motility e.g. loperamide
anti-spasmodics e.g. buscopan and peppermint oil
laxatives e.g. isphagula, lactulose, senna, archacis oil
what is the action of pro kinetics?
increase gut motility and increase gastric emptying
increase parasympathetic control of smooth muscle and sphincter control via Ash
how does loperamide work?
(also known as immodium)
work via opiate receptors in GI tract to decrease Ach release.
this decreases smooth muscle contraction and therefore increase anal sphincter tone.
what type of anti-spasmodic is buscopan and how does it work?
anti-cholinergic muscarinic antagonist
inhibits smooth muscle contraction in gut wall therefore = relaxation
what type of anti-spasmodic is peppermint oil and how does it work?
calcium channel blocker
reduces ca required for smooth muscle contraction
what are the 4 types of laxative?
bulk e.g. isphagula
osmotic e.g. lactulose
stimulant e.g. senna
softness e.g. arachis oil
what are the problems with laxatives?
- can cause obstruction
- need for other measures (with osmotic laxatives they won’t work if you don’t have adequate fluid intake)
- misuse
what are the main drug types/names used for IBS-C?
pro kinetics
anti spasmodics i.e. buscopan and peppermint oil
laxatives
what are the main drug types/names used for IBS-D?
anti-motility i.e. Loperamide
anti-spasmodics i.e. buscopan and peppermint oil
what is a problem with loperamide?
has a few central opiate effects as it is not well absorbed across the blood brain barrier
what are the main drug types for treating inflammatory bowel disease and give an example of each.
aminosalicylates e.g. mesalazine and omezalazine
steroids
immunosuppressants e.g. azathioprine and methotrexate
biologics (anti TNFalpha antibodies) e.g. infliximab
how does biologics such as infliximab work to reduce inflammation?
infliximab is a anti TNF alpha antibody.
it prevents the action of TNF which is a pro inflammatory cytokine
how does immunosuppressants such as azathioprine work to reduce inflammation?
prevents the formation of purines required for DNA synthesis therefore prevents immune cell proliferation
what are the problems associated with the use of immunosuppressants such as azathioprine for the treatment of IBD?
adversely affects bone marrow
hypersensitivity
organ damage (lung, liver and pancreas)
what are the problems associated with aminosalicylates for the treatment of IBD?
GI upset
blood dyscrasis
renal impairment
what are the problems associates with the use of steroids?
osteoporosis
cushing features i.e. weight gain, diabetes, hypertension
increased susceptibility to infection
addison crisis with sudden withdrawal
what are the contraindications for anti TNF alpha antibodies?
TB
MS
serious infection
pregnancy/breast feeding
What are the adverse effects of biologics such as infliximab which is used for the treatment of IBD?
risk of infection (esp. TB)
infusion reaction i.e. fever, rash
anaemia, thrombocytopenia, neutropenia
demyelination (disseminated malignancy)
what are the main pharmacodynamic changes in a patient with chronic liver disease?
exaggerated response
reduced response
increased toxicity
why is the distribution of drugs in someone with chronic liver disease affected?
chronic liver disease causes a patient to have low albumin
low albumin = decreased binding and increased free drug concentration
what classification is used to determine the extent of liver disease?
child-pugh classification
when prescribing drugs to a patient who has chronic liver disease, what do you have to take care with/avoid?
drugs which are hepatotoxic such as methotrexate and azathioprine
drugs which may worsen the non-liver aspects of liver disease (encephalopathy) such as benzodiazepines
what particular drugs should you avoid if a patient has chronic liver disease?
Warfarin
Aspirin/NSAIDS
Opiates/benzodiazepines
what are the risk actors for getting GI adverse effects from drugs?
age female alcohol consumption genetics malnourishment
what drug type can cause changes to gut bacteria?
and what are the effects that changing gut bacteria can have?
anti biotics
- reduction in vitamin K absorption = increased prothrombin time
- require gut bacteria to convert inactive drugs into active, therefore if its disturbed it may impact the effectiveness of the oral contraceptive pill
- overgrowth of pathogenic bacteria such as clostridium difficile
what drug types can cause peptic ulceration and GI bleeding?
low dose aspirin
NSAIDS
Warfarin
what drug types can cause diarrhoea / constipation?
constipation = anticholinergics, NSAIDS, antimicrobials diarrhoea = NSAIDS, opioids, cholinergics
what are the 2 types of drug induced liver injury?
Type A - intrinsic hepatotoxicity (predictable, dose related)
Type B - idiosyncratic hepatotoxicity (unpredictable, not dose dependant)
what are the adverse effects of aminosalicylates?
GI upset
blood dyscrasia
renal impairment
what are the adverse effects of steroids?
osteoporosis
cushings - weight gain, hypertension, diabetes
increased susceptibility to infection
addison crisis with sudden withdrawal
what are the adverse effects of anti-TNF alpha antibodies?
risk of infection esp. TB infusion reactions - rash, fever anaemia thrombocyopenia neutropenia demyelination - disseminated malignancy
what are the adverse effects with proton pump inhibitors?
GI upset
predisposition to clostridium difficile
hypomagnesaemia
B12 deficiency
in patients with chronic liver disease, what is the problem with the metabolism of drugs?
they have an increased gut bacteria therefore metabolise drugs quicker so higher dose is needed
Liver disease may reduce first pass metabolism
what are the risk factors for experiencing GI adverse effects from drugs?
age female alcohol consumption genetics malnourishment
how does antibiotics affect the gut and what effects does this have?
Antibiotics cause changes to gut bacteria
Gut bacteria converts inactive drugs to active ones (i.e. the pill) therefore this results in certain drugs not being effective
Reduces vitamin K absorption = increased prothrombin time
Overgrowth of pathogenic bacteria i.e. C.difficile
what are the two types of drug induced liver hepatotoxicity?
intrinsic - dose related, predictable (type A)
idiosyncratic - unpredictable, not dose related (type B)
in the child Pugh classification of severity of liver disease, what are the values for groups A, B and C?
A = > 7 B = 7-9 C = >9
which drugs are hepatotoxic?
methotrexate
azathioprine
what drug may worsen the non liver aspects of liver disease?
opiates/ benzodiazepines
encephalopathy
what type of drug can worsen ascites and how?
NSAIDS
due to fluid retention
