260 Section 7/ Drugs Acting on GITthe 5-HT 4 receptor in the presynaptic nerve
endings in the myenteric plexus promoting
the release of acetylcholine at the neuro-
muscular junction, strengthening tone and
contractions of the gut wall, in particular the
tone of the lower oesophageal sphincter.
Adverse effects include nausea and
diarrhoea.
It is indicated in gastroesophageal reflux
disease and functional dyspepsia, diabetic
gastropathy.
Renzapride is also a selective 5-HT 4
receptor agonist.
ITOPRIDE
It is a novel prokinetic agent, it inhibits
dopamine D 2 receptors at the parasympa-
thetic nerve endings and thereby increas-
es the release of acetylcholine. It decreases
the metabolism of acetylcholine by inhibit-
ing the enzyme acetylcholinesterase.
It is highly protein bound (approx. 96%),
metabolised in the liver by N-oxidation to
inactive metabolites by the enzyme flavin-
containing monooxygenase. It is excreted
mainly by the kidneys in the form of
metabolites and as unchanged drug.
Adverse effects include rash, itching
sensation, tremor, increase in SGOT, SGPT
levels, diarrhoea, abdominal pain, gyneco-
mastia etc.
It is indicated in upper abdominal
digestive symptoms associated with chronic
gastritis.