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9780521704632c19 CUFX213A/Peck 9780521618168 December 28, 2007 14:1
Section IVOther important drugs
Gut–its peripheral actions result in an increased lower oesophageal sphincter tone
and relaxation of the pylorus. It has no effect on gastric secretion.
Cardiovascular – acute conduction abnormalities follow rapid intravenous admin-
istration, and acute hypertension occurs in phaeochromocytoma.
Metabolic – it may precipitate hyperprolactinaemia and galactorrhoea, and should
be avoided in porphyria. It inhibits plasma cholinesterase activity in vitro and may
therefore prolong the effects of drugs metabolized by this enzyme.Kinetics
Metoclopramide is well absorbed from the gut although first-pass metabolism varies
significantly producing a wide range in oral bioavailability (30–90%). It may be given
intravenously. It is conjugated in the liver and excreted along with unchanged drug
in the urine.Domperidone
This dopamine antagonist is less likely to cause extrapyramidal effects as it does not
cross the blood–brain barrier. Its use in children is limited to nausea and vomiting
following chemotherapy or radiotherapy. It also increases prolactin levels and may
cause galactorrhoea and gynaecomastia. The intravenous preparation was with-
drawn following serious arrhythmias during administration of large doses. It is only
available as tablets or suppositories.Mucosal protectors
Sucralfate
Sucralfate exerts a generalized cytoprotective effect by forming a barrier over the
gut lumen. It protects ulcerated regions specifically. It does not alter gastric pH,
motility or lower oesophageal sphincter tone, although it has been reported to have
bacteriostatic effects.
Itsactions are due to its local effects and virtually none is absorbed from the gut.
Consequently it has no effect on the central nervous or cardiorespiratory systems.Effects
Gut–minor gastric disturbances. Enhanced aluminium absorption in patients
with renal dysfunction or on dialysis. It may reduce the absorption of certain drugs
(ciprofloxacin, warfarin, phenytoin and H 2 antagonists) by direct binding.Prostaglandin analogues
Misoprostil
Misoprostil is a synthetic analogue of prostaglandin E 1.