PRODUCT INFORMATION
GASTRO-STOP
COMPOSITION
Loperamide hydrochloride.
DESCRIPTION
Chemical name: 4-(4-chlorophenyl)-4-hydroxy-N,N-dimethyl-α,α-diphenyl-l-piperidinebutyramide monohydrochloride.
Empirical formula: C29H33ClN2O2 HCl.
Molecular weight: 513.49.
GASTRO-STOP capsules contain 2 mg loperamide hydrochloride as the active ingredient.
They also contain lactose, magnesium stearate, povidone, sodium starch glycollate and
starch-maize.
ACTIONS
Antidiarrhoeal agent.
Pharmacology
Antidiarrhoeal Activity. Although the exact mechanism of action of loperamide has not been
confirmed, it is thought that it has a direct effect on the gastrointestinal wall by interacting
locally with cholinergic as well as noncholinergic neuronal mechanisms involved in the
peristaltic reflex. The latter effect may be related to the high affinity of loperamide to bind
opiate receptors in vitro.
Loperamide has been shown to effectively combat experimentally induced diarrhoea in
animals, and also to inhibit gastrointestinal motility in humans.
The mode of action of loperamide is believed to be a direct effect on the circular and
longitudinal muscles of the intestinal wall. In man, as a constipating agent, loperamide on a
mg to mg basis is about 3 times more potent than diphenoxylate hydrochloride and 25 times
more potent than codeine phosphate.
Clinical improvement occurs within 1 to 3 hours following loperamide administration (4 mg
dose). In normal test subjects, a single 4 mg dose of loperamide has been reported to
significantly increase the median time of defecation from 23 to 41 hours.
Pharmacokinetics
Loperamide, following partial absorption in the gastrointestinal tract, is reported to undergo
considerable first-pass metabolism in the liver, and to be excreted predominantly in the
faeces. The elimination half-life is reported to be about 10 hours.
INDICATIONS
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Control and symptomatic treatment of acute non-specific diarrhoea.
CONTRAINDICATIONS
Patients known to be hypersensitive to loperamide. It is contraindicated in patients who are
constipated and also in whom constipation should be avoided (see PRECAUTIONS, Use in
Pregnancy).
Antiperistaltic agents should not be used in acute diarrhoea associated with organisms that
penetrate the intestinal mucosa; e.g. toxigenic E.coli, Salmonella, Shigella and in pseudomembranous colitis associated with broad spectrum antibiotics.
Use in Children
Contraindicated in children under 12 years.
WARNINGS
Fluid and electrolyte depletion may occur in patients who have diarrhoea. Patients taking
Gastro-Stop should take adequate fluids or consider appropriate fluid and electrolyte therapy.
In some patients with acute ulcerative colitis or in Crohn's disease, agents that inhibit
intestinal motility or delay intestinal transit time have been reported to induce toxic
megacolon. Gastro-Stop therapy should be discontinued promptly if abdominal distension
occurs or if other untoward symptoms develop in patients with acute ulcerative colitis or
Crohn's disease.
Gastro-Stop should not be used in the case of acute dysentry, which is characterized by blood
in stools and elevated temperature.
PRECAUTIONS
In acute diarrhoea, if clinical improvement is not observed in 48 hours, administration should
be discontinued.
Abuse and Dependence. Physical dependence in humans has not been observed. In animals,
at high doses, loperamide has been shown to produce symptoms of physical dependence of
the morphine type.
Hepatic and Renal Disease. Caution should be used in patients with advanced liver disease;
e.g. cirrhosis, on the basis of possible enterohepatic pathway because of likely accumulation
of adverse effects on liver function. Caution should also be used in patients with advance
renal disease; e.g. renal failure. Possible accumulation may occur also as a result of the
excretory pathway.
Anticholinergic Effects. Caution should be used in patients with glaucoma, urinary bladder
neck obstruction, pyloric obstruction, significant gastric retention, or intestinal stasis, because
loperamide has been shown to demonstrate anticholinergic properties.
Use in Pregnancy (Category B3)
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Safe use of Gastro-Stop during pregnancy has not been established. Gastro-Stop should be
used in pregnant women only when clearly needed.
Use in Lactation
It is not known whether Gastro-Stop is excreted in human milk. As a general rule, nursing
should not be undertaken while a patient is on a drug, since many drugs are excreted in
human milk.
Use in Children
Contraindicated in children under 12 years.
Interactions with other Drugs
Although the pharmacological effect of loperamide hydrochloride is not associated with a
central action, patients with concomitant administration of tranquillisers or alcohol should be
carefully observed.
Theoretically, a combination of Gastro-Stop with MAO inhibitors (which are also inhibitors
of liver microsomal enzymes) are liable to potentiate the action of loperamide by blocking its
metabolic pathway.
ADVERSE REACTIONS
Adverse experiences which have been reported with loperamide are generally of a minor and
self limiting nature. The more common adverse effects are difficult to distinguish from
symptoms associated with the diarrhoeal syndrome.
More Common Reactions
Gastrointestinal.
Flatulence, constipation, nausea, abdominal pain.
Less Common Reactions
Auditory and Vestibular.
Giddiness.
Dermatological.
Rash.
Gastrointestinal.
Anorexia, vomiting, bad taste (e.g. metallic taste).
Genitourinary.
Decreased sexual drive, polyuria.
Nervous System.
Headache, weakness, fatigue, subjective feeling of unrest, dry
mouth.
Ocular.
Blurred vision.
DOSAGE AND ADMINISTRATION
Gastro-Stop capsules are administered orally.
Caution. Gastro-Stop capsules are contraindicated in children under the age of 12
years.
Acute Diarrhoea
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The recommended initial dose of Gastro-Stop in adults is 2 capsules (4 mg) followed by 1
capsule (2 mg) after each unformed stool. Daily dose should not exceed 8 capsules (16 mg).
Clinical improvement is usually observed within 48 hours.
OVERDOSAGE
Symptoms
Overdosage in humans may result in constipation, CNS depression and gastrointestinal
irritation.
Treatment of overdosage
Contact the Poisons Information Centre on 13 11 26 for advice.
PRESENTATION
Hard capsule with green cap and dark gray body, with “LOP2” printed on cap and body.
Pack sizes: 6's*, 8’s*, 12’s and 20’s.
(*not currently distributed in Australia)
STORAGE
Store below 30°C. Protect from light.
POISONS SCHEDULE
S2 – Pharmacy Medicine
SPONSOR
Aspen Pharmacare Australia Pty Ltd
34-36 Chandos St
St Leonards NSW 2065
AUSTRALIA
DATE OF TGA APPROVAL
Approved by the Therapeutic Goods Administration: 28 April 1994
Rescheduling approved by TGA: 25 July 2000
Date of latest amendment: 12 July 2010
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