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Block 3 Pharmacology > Drugs and the Gut > Flashcards

Flashcards in Drugs and the Gut Deck (62)
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1
Q

Antagonist

A

A drug or chemical that interferes with the physiological action of another, especially by combining with and blocking its receptor
Agonist:

2
Q

Agonist

A

A drug or chemical that can combine with a receptor on a cell to produce a physiologic reaction typical of a naturally occurring substance.
Receptor:

3
Q

Receptor

A

Any of various specific protein molecules in surface membranes of cells and organelles to which complementary molecules, eg hormones, neurotransmitters, may be bound.

4
Q

Irreversible binding

A

Irreversible binding: An irreversible antagonist binds covalently to the receptor and cannot be displaced by either competing ligands or washing.

5
Q

Side effect

A

Problems that occur when treatment goes beyond the desired effect. Or problems that occur in addition to the desired therapeutic effect

6
Q

what is Abdominal discomfort indicative of

A

Peptic Ulcer (upto 1 in 8 people)
Gastro esophageal reflux
Vomiting

7
Q

where do peptic ulcers form

A

Form in stomach (Stomach ulcer) or the digestive tract (duodenal ulcers).

8
Q

symptoms of peptic ulcers

A
Pain intheabdomen/neck/navel/back. 
Bleeding
Indigestion
Heartburn
Loss of appetite
Vomiting
Can no longer tolerate fatty foods
9
Q

pain of peptic ulcer

A

Can last from a few minutes to a few hours
If a stomach ulcer usually startssoonafter eating a meal.
If the ulcer is in your small intestine, pain may start two to three hours after eating.

10
Q

describe the pain of stomach ulcers

A

no typical symptoms and can cause no pain

11
Q

how does plain work in stomach ulcers

A

get complication withoutpain.

12
Q

where are neck cells

A

cardiac, pylori, fundus

13
Q

where are chief cells found

A

fundus

14
Q

where is parietal/oxyntic

A

fundus

15
Q

what do the gastric glands secrete

A

gastric Juice ( HCL + enzymes + mucus

16
Q

what does Neck cells secrete

A

mucus

17
Q

what does Chief cells secrete

A

proteolytic enzymes (digestive)

18
Q

what does Parietal / oxyntic cells secrete

A

HCL

19
Q

how is acid secreted

A

H+ ion is pumped into the lumen, in exchange for K+ via proton pump

20
Q

where is hydrogen ion generated and what happens after

A

Hydrogen ions are generated within the parietal cell from dissociation of water. The hydroxyl ions formed in this process rapidly combine with carbon dioxide to form bicarbonate ion, a reaction cataylzed by carbonic anhydrase.

21
Q

what happens after Bicarbonate is transported out of the basolateral membrane in exchange for chloride

A

. The outflow of bicarbonate into blood results in a slight elevation of blood pH known as the “alkaline tide”. This process serves to maintain intracellular pH in the parietal cell.

22
Q

how are Chloride and potassium ions are transported into the lumen of the cannaliculus and why is this important

A

conductance channels and such is necessary for secretion of acid.

23
Q

what happens when hydrogen ions are pumped out of the cell into the lumen

A

this is done in exchange for potassium through the action of the proton pump; potassium is thus effectively recycled

24
Q

what happens when there is an accumulation of osmotically active hydrogen ion in the cannaliculus

A

generates an osmotic gradient across the membrane that results in outward diffusion of water - the resulting gastric juice is 155 mM HCl and 15 mM KCl with a small amount of NaCl.

25
Q

what causes peptic ulcers

A

Underlying mechanism

Disruption of stomach lining cause tissue damage by stomach acid

26
Q

what pH is needed for healing

A

more than 3

27
Q

mechanism of action of H.pylori

A

Urease (to produce NH3 + H2CO3)
Induces inflammation (Gastritis)
disrupts the lining of the stomach -> stomach acid infiltrates -> ulcer

28
Q

how much of the population have H.pylori

A

50%

29
Q

is H pylori negative or positive

A

negative

30
Q

true or false Once infected bacteria may remain in the stomach for life

A

true

31
Q

true or false Most people there are no symptoms

A

true

32
Q

true or false can trigger ulcers in 10-25% of those infected

A

false Can trigger ulcers in 10-15% of those infected

33
Q

what do PPI do

A

decrease H+ secretion by parital cells

34
Q

what is interesting about the coating of PPI

A

Prodrugs,
enteric coating prevents rapid exposure to stomach HCl
However some use a bicarbonate coat to alter stomach pH and protect the PPI

35
Q

what cells take up PPI

A

parietal cells

36
Q

PPIs

A

Prodrugs,
enteric coating prevents rapid exposure to stomach HCl
However some use a bicarbonate coat to alter stomach pH and protect the PPI
Taken up by Parietal cells
At acidic pH conversion sulfenamides

Irreversible inhibition of H+-pump via ATPase

37
Q

Proton Pump Inhibitors dose

A

Elimination half-life of PPIs
0.5 to 2.0 hr,
Single dose persists up to three days.
Due to
Accumulation of the drug in parietal cell canaliculi
the irreversible nature of proton pump inhibition

38
Q

antagonist of H2 receptor targeting

A

Cimetidine, Ranitidine, Nizatidine

39
Q

future of antagonist of H2 receptor targeting

A

Well tolerated generally

But replaced by PPIs due to better effect and safety profile

40
Q

treatment of H.pylori

A

Eradication of Helicobacter pylori with antibiotics:Amoxicillin + clarithromycin
Amoxicillin + metronidazole
Combined therapy with PPI

41
Q

can NSAIDS can cause ulcer formation?

A

yes

42
Q

COX 1 inhibited by

A

NSAID .

43
Q

COX 2nhibited by

A

NSAIDS

COX 2 INHIBITIORS

44
Q

COX 1 examples

A

prostagladins

thromboxanes

45
Q

COX 2 examples

A

prostaglandins

prostacyclins

46
Q

Prostaglandin receptors eg PGE Misoprostol

A

prostaglandins
decrease gastric acid secretion

increase mucus and HCO3- stomach secretion

Both of these are important in maintaining the stomach lining

With NSAIDs Misoprostol can be given
Mechanism:
decrease cAMP in parietal cells proton pump activity decrease

47
Q

what is vomitting

A

Vomiting a reflex triggered by a signal from the brain.

48
Q

Frequency and signals to induce vomiting

A
Physical injury   (remember retching as well)
Electrolyte/fluid imbalance
49
Q

internal causes of vomiting

A
headache 
viral infection
heart attack
severe pain
abdominal source apprendictis hapatisis kidney or gallbladder issue
pregnacy
50
Q

external causes of vomiting

A

motion sickness
alchol poisoning
food poisining
medcinine

51
Q

Motion sickness Muscarinic antagonists

A

(Hyoscine)

Not specific eg blurred vision, dry mouth, relaxes gut

52
Q

Histamine antagonists

A

(Cinnarizine / Cyclizine / Promethazine)

Side-effects drowsiness + dry mouth

53
Q

Pregnancy related sickness: Thalidomide

A

Originally a sleeping tablet
But then prescribed off-label for vomiting#
Caused phocomelia

54
Q

Chemotherapy induced vomiting

A

5HT3 antagonists
Reduce activity of the vagus nerve – used to stimulate vomiting reflex
Few side effects
Ondanestron, Granisetron
Used in conjunction with dexamethasone to improve efficacy

55
Q

Chemotherapy induced vomiting. Metoclopramide

A

Acts on CTZ and increases motility of digestive tract
But unwanted side-effects – disorders of movement, fatigue, stimulates prolactin release, and causes disorders of menstruation

56
Q

Chemotherapy induced vomiting. Domperidone

A

Acts on both gut and CTZ

Does not cross blood brain barrier

57
Q

Phenothiazines

A

Used after nausea induced by cancer/radiation therapy/ cytotoxic drugs
Unwanted side-effects common - dystonia (Neurological movement disorder) and tardive dyskinesia.

58
Q

Conclusions

A

Peptic Ulcers are caused by Bacterial infection
Multiple mechanisms for targeting pH in the stomach
Vomiting is a reflex mechanism
There are multiple reasons for vomiting to occur, and therefore multiple sites for pharmacological intervention

59
Q

cause of motion sickness

A

conflict between what ur eyes see and what your inner ears which help with balance, sense

60
Q

prevention of motion sickness

A

more serious motion sickness can be treated with medication such as Hyoscine. Ginger has also been used as a treatment for centuriess

61
Q

3-12 is when travel sickness happens, usually more men than women. true or false

A

true

62
Q

30% have motion sickness regularly on journeys by road, sea or air. true or false.

A

true