Pharmacology Flashcards
What are the types of GI drug?
Acid suppressants Drugs affecting motility Laxatives IBD drugs Drugs affecting intestinal secretions
What are the types of acid suppressants?
Antacids
H2 receptor antagonists
Proton pump inhibitors
What drugs affect GI motility?
Anti-emetics
Antimuscarinics/other antispasmodics
Antimotility
What are the types of IBD drug?
Aminosalicylates
Corticosteroids
Immunosuppressants
Biologics
What are the types of drug affecting intestinal secretions?
Bile acid sequestrates
Urodeocycolic acid
How do antacids work?
Neutralise gastric acid
What are alginates?
A type of antacid that works by forming a viscous gel that floats on stomach contents and reduces reflux
How do H2 receptor antagonists work?
Block histamine receptor, and thereby reducing acid secretion
When are H2indicated for use?
GORD
Peptic ulcer disease
How are H2 receptor antagonists given?
Oral or IV
How do proton pump inhibitors work?
Block proton pump and thereby reduce acid secretion
When are proton pump inhibitors indicated for use?
GORD
Peptic ulcer disease
Triple therapy for treatment of PU/DU associated H pylori
What are the problems associated with proton pump inhibitor use?
GI upset
Predisposition to c. diff, hypomagnesaemia, B12 deficiency
What do pro kinetic agents do?
Increase gut motility and gastric emptying
What are pro kinetic agents used for?
Gastroparesis
GORD
as antiemetics
How do prokinetics work?
Unclear
Involves parasympathetic nervous system control of smooth muscle and sphincter tone
What can drugs which decrease motility be used for?
Clinical benefit i.e. antidiarrhoea
Cause unwanted effects i.e. constipation
How do drugs decreasing motility work?
Via opiate receptors in GI tract to decrease Ach release, decreasing smooth muscle contraction and increasing anal sphincter tone
What are antispasmodics used for?
IBS
Renal colic
What are the 3 mechanisms of antispasmodics action?
Anti cholinergic muscarinic antagonists
Direct smooth muscle relaxants
CCBs reducing Ca required for smooth muscle contraction
What are the 4 types of laxatives?
Bulk
Osmotic
Stimulant
Softeners
What are the issues associated with laxatives?
Obstruction
Route of adminisation
Need for other measures
Misuse
Wat is the mechanism of action of aminosalicylates?
Unclear but anti inflammatory
What are the adverse effects of aminosalicylates?
GI upset
Blood dycrasias
Renal impairment
How do corticosteroids work?
Antiinflmmatory
What are the complications of corticosteroids?
Increases susceptibility to infection
Addisonian crisis with abrupt withdrawal
How do immunosuppressants work?
Prevents formation of purines required for DNA system thesis so reduces immune cell proliferation
What are the adverse effects of immunosuppressants?
Mainly relate to bone marrow suppression
Asatioprine hypersensitivity
Organ damage
How do biologics work?
Addresses inflammatory response but not underlying disease process
What are the contraindications for biologics use
Current TB or other serious infection
MS
Pregnancy/breastfeeding
What are the adverse effects of biologics?
Risk of infection, esp TB Infusion reaction Anaemia, thrombocytopenia, neutropenia Demyelination Malignancy
How does cholestryamine work?
Reduces bile salts by binding with them in the gut and then excreting them as an insoluble complex
What is ursodeoxycholic acid used to treat>
Gallstones and primary biliary cirrhosis
How does ursodeoxycholic acid work?
Inhibits an enzyme involved in the formation of cholesterol, altering the amount of bile and slowly dissolving non calcified stones
What can affect the ADME processes of a drug?
Gi or liver disease
What can affect the absorption of a drug?
pH
Gut length
Transit time
What can affect the distribution of a drug and how?
Low albumin- decreased binding and increased free drug concentration
What can affect the metabolism of a drug?
Liver enzymes
Gut bacteria
Gut wall metabolism
Liver blood flow
What are the most common GI adverse effects?
GI upset COnstipation/diarrhoea GI bleeding/ulceration Changes to gut bacteria Liver injury
What causes changes to gut bacteria?
Mainly antibiotics
What can changes in gut bacteria cause?
Loss of OCP activity
Reduced vit K absorption
Overgrowth of pathogenic bacteria
What are the 2 types of drug induced liver injury?
Intrinsic hepatotoxicity
Idiosyncratic hepatotoxicity
What is intrinsic hepatotoxicity?
Predictable, dose dependent, acute reaction
What is idiosyncratic hepatotoxicity?
Unpredictable, not dose dependent, may occur at amy time and be part of hypersensitivity reaction
What are the risk factors for drug induced liver injury?
Age Female Alcohol consumption Genetic factors Malnourishment
How is the severity of liver disease classified?
Child-Pugh classification
What does the Child-Pugh classification look at?
Bilirubin Albumin PT Encephalopathy Ascites
What are the 2 year survival rates in the Child-Pugh classification system?
<7= 85% 7-9= 57% >9= 35%
When should care be taken when prescribing in patients with liver disease?
Drugs which can be toxic due to changes in pharmacokinetics
Drugs with hepatotoxicity or may worsen non liver aspects of liver disease
Warfarin/anticoagulents
Aspirin/NSAIDs
Opiates/benzodiazepines
Why must care be taken in liver disease with warfarin/anticoagulents?
Clotting factors already low
Why must care be taken in liver disease with aspirin/NSAIDs?
Increase bleeding time
Worsen ascites
Why must care be taken in liver disease with opiates/benzodiazepines?
May precipitate encephalopathy by increasing sedation
