Gastrointestinal drugs
Department of pharmacology
Liming zhou
2010,spring
classification

Drugs for treatment of peptic ulcers
 Drugs for adjusting the function of
digestion
 Drugs promoting gastrointestinal motility
 Antiemetic drugs
 laxatives
Drugs for peptic ulcers
Classification of peptic ulcer:

Duodenal (DU) Gastric (GU)
 Role of pepsin in peptic ulcer disease:
 Secreted gastric acid plus effects of
pepsin promote tissue injury

Peptic ulcer disease: an imbalance between
aggressive factors (gastric acid pepsin bacteria)
and protective factors (gastric mucus,
bicarbonate, prostaglandins)

Regulation of gastric acid secretion-- many
factors (chemical, neural, hormonal)
 Stimulation:
 Gastrin-most
potent stimulant
 Activation of postganglionic
vagal fibers
 Drugs
for peptic ulcers-----antacids
Action
 Neutralize secreted acid
 Reduce gastric acidity
Pepsin inactive
Reduce destroy factors

Drugs for peptic ulcers-----antacids
 A magnesium hydroxide(氢氧化镁)
 B magnesium trislilicate（三硅酸镁）
 C aluminum hydrocide（氢氧化铝）
 D Calcium carbonate（碳酸钙）
 F Sodium bicarbonate（碳酸氢钠）
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1 NaHCO3+HCl
NaCl+H2O+CO2
2 Al（OH）3 aluminium hydroxide
Al（OH）3+3HCl
AlCl3 +3H2O
3 Mg（OH）2 magnesium hydroxide
Mg（OH）2+2HCl
MgCl2 +2H2 O
4 Mg2Si3O8 magnesium trisilicate
Mg2Si3O8+4HCl
2MgCl2+3SiO2+2H2O
5 CaCO3 calcium carbonate
CaCO3+2HCl
CaCl2+H2O+CO2
 Gastric
antisecretory drugs
 antagonisit of H2 receptor
↓
 decrease the H+ secretion
 Basal
gastric acid
food-stimulated gastric acid

H2 Receptor Antagonists

A cimetidine (西米替丁) +
B ranitidine （雷米替丁）++
C famotidine（法莫替丁）+++
Effective inhibitor of stimulated and nonstimulated gastric acid secretion
Healing rates: similar between antacids and H2
receptor antagonists




 Effective
inhibitor of stimulated and
non-stimulated gastric acid secretion
 Healing rates: similar between
antacids and H2 receptor
antagonists
Mucosal protective agents
 Prostaglandins

reduction in basal and stimulated gastric
acid secretion;
 enhanced mucosa resistance to injury
(PGE1/PGE2).
Mucosal protective agents

Bismuth compounds

Mechanism of Action
cytoprotective effects
compounds bind to the ulcer base, stimulating
mucus and prostaglandin production
antibacterial effect
inhibition of proteolytic, lipolytic, and urease
activities
Coating and protecting the ulcer crater

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Clinical use of Bismuth compounds
 In monotherapy:

------- eradicate H. pylori in
about 20% of patients
 combination with antibiotics

-------eradicate H. pylori in up to 95%
of patients.



Sucralfate
binds to ulcer bed (granulation tissue, not to
gastric or duodenal mucosa)
 decreases proton diffusion to the ulcer base
 may increase endogenous tissue prostaglandins
and may bind epidermal growth factors and
other growth factors-- improving mucosal
defense

antimicrobials
 activity against H.pylori
 clarithromycin, amoxicillin, tetracycline
Drugs for adjusting the function of
digestion

drugs of aid digestive

A pepsin

B pancreatin

C lactasin
antiemetic drugs and drugs promoting
gastrointestinal motility
 antiemetic

drugs:
H-1 receptor blocker : diphenhydramine
 Chloropromazine
 M-receptor blocker : scopolamine

drugs promoting gastrointestinal motility
 Metoclopramide (甲氧氯普胺)：
 domperidone （多潘立酮）blocking D2receptor
 Cisapride(西沙比利）

Metoclopramide (甲氧氯普胺)
1)
Blocking the DA2 receptor in
CTZ
Blocking the DA2 receptor in
2)
Gastrointestinal

domperidone （多潘立酮）

blocking DA2-receptor in
Gastrointestinal

Cisapride(西沙比利）

Increase release of the Ach

antidiarrheal drugs
 opium preparation
 Laxative Drugs
magnesium sulfate
sodium sulfate