IBD And IBS Flashcards
Inflammatory Bowel Disease
Severe inflammatory disorder affecting the lower GI tract
- inflammation is destructive and painful
- perforation can occur, which can be fatal
Two types of IBD
Crohn’s Disease
Ulcerative colitis
IBD treatment addresses
Inflammation and immune response
Drug classes for IBD (4)
Aminosalicylates
TNF inhibitors
Corticosteroids
Immunosuppressants
Aminosalicylates example
5-Aminosalicylic Acid (5-ASA)
- also known as mesalamine
Extended Release Microspheres (5-ASA ER)
Aminosalicylates mechanism
- Inhibit inflammatory mediators
- may also inhibit cyclooxygenase
Aminosalicylates pharmacokinetics
- act locally (target colon)
- strategies: Prodrug cleaved in colon, enteric coating dissolved in colon, microspheres release drug slowly, rectal administration.
Aminosalicylates Prodrug
Sulfasalazine
Sulfasalazine mechanism
5-ASA + sulfapyridine
- two molecules separated in colon by bacteria
- efficacy largely due to 5-ASA
- adverse effects due to sulfapyridine
Extended Release Microspheres mechanism
Release 5-ASA throughout the small intestine to rectum
Rectal Suppositories
Suppositories effects may extend to the upper rectum (10-15cm)
Rectal (Enema)
Enemas reach further than suppositories, up to the distal colon
Aminosalicylates Side Effects
Gastrointestinal (worse with sulfasalazine)
Headache
Other rare ones but serious harms
TNF alpha inhibitors
TNF alpha is a key mediator of inflammation
Appears to be particularly important in IBD
TNF alpha inhibitor example
Monoclonal antibodies
Infliximab
TNF alpha inhibitors mechanism
MAbs bind to TNF and prevent it from interacting with its receptor
TNF alpha inhibitors side effects
Opportunistic infections
- Immunosuppressive effects may increase the risk (réactivation of tuberculosis)
- Hypersensitivity reactions: acute or delayed, infliximab is chimeric (animal/human)
- malignancies: due to reduced immune surveillance, TNF lyses tumor cells
Corticosteroids mechanisms
Anti-inflammatory effects
Immunosuppressive
Prednisone and Budesonide
Corticosteroids routes
Oral, rectal, parenteral
Corticosteroids side effects
- Numerous serious side effects with systemic agents like Prednisone
- Fewer with Budesonide
Immunosuppressants example
Antimetabolites
- Azathioprine
Azathioprine mechanism
- converted to a structural analogue of guanine
- “false nucleotide” halts DNA/RNA synthesis
- Immune cells (lymphocytes) rely on de novo purine synthesis: therefore more susceptible to actions of metabolites
Immunosuppressants side effects
Infection
Cancer
Bone marrow suppression
Gastrointestinal
Cyclosporine mechanism
Inhibits T-cell activation by inhibiting IL-2
Cyclosporine is difficult to use because..
Narrow margin for safety
Many drug interactions
Significant adverse effects
Other Immunosuppressants
Methotrexate
Folate antagonist
- significant adverse effects
Irritable Bowel Syndrome
Very common, challenging to treat
- Constipation, diarrhea or mixed
- abdominal pain
- psychological, dietary components
Antispasmodics
- anticholinergics
- calcium antagonists
Anticholinergics example
Hyoscine
Anticholinergics mechanism
Muscarinic receptors stimulate peristalsis in the GI tract
- blocking M receptors inhibits contractions of the colon
Anticholinergic side effects
- Dry mouth
- urinary retention
- constipation
Calcium antagonist example
Pinaverium
Calcium antagonists mechanism
Blocks entry of Calcium into smooth muscle cells of the GI tract
- calcium plays a role in smooth muscle contraction
Calcium Antagonists side effects
- constipation
- Abdonminal distension
Serious: esophageal irritation - patients should take with a full glass of water/small snack to make sure drug clears the esophagus
IBS managing pain and constipation (drug name)
Linaclotide - cGMP agonist: increases intestinal secretions and reduces transmission of pain signals
Anti-depressants used in treatment of IBS
- tricyclic antidepressants
- serotonin selective reuptake inhibitors
Tricyclics antidepressant used in IBS
Amitriptyline
Tricyclics antidepressant side effects
- exhibit side effects similar to anticholinergic (dry mouth, constipation, and urinary retention)
- Better for use in IBS-D than SSRI’s
SSRI example
Citalopram
SSRI use in IBS
Typically used to treat IBS-C but the effects on the GI are not as reliable as TCA