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Omesec
PRODUCT DESCRIPTION
Hard gelatin capsule with flesh opaque body and light brown
opaque cap, each half printed with 'OMESEC 20' in black,
holding enteric-coated mini-tablets.
COMPOSITION
Active Ingredient : Omeprazole 20 mg/capsule
Preservatives : None
PHARMACOLOGICAL ACTION
Omeprazole is a proton-pump inhibitor and thus prevents
the secretion of gastric acid. Omeprazole is a weak base and
is activated at an acidic pH to a sulphonamide derivative that
binds irreversibly to Hydrogen/Potassium Adenosine
Triphosphatase (H+/K+ ATPase) enzyme system, the so-called 'proton pump' that is found at the secretory surface of
parietal cells. It thereby inhibits the final transport of
hydrogen ions (via exchange with potassium ions) into the
gastric lumen. Omeprazole inhibits both basal and
stimulated acid secretion irrespective of the stimulus. It also
inhibits hepatic cytochrome P-450 mixed function oxidase
system.
PHARMACOKINETICS
Omeprazole is rapidly absorbed, but to a variable extent
following oral administration. The absorption of Omeprazole
is formulation-dependent and dose-dependent but it is not
affected by food. Omeprazole in the form of enteric-coated
mini-tablets is absorbed from the small intestines and
delivered via the bloodstream to the parietal cell. Oral
absorption of the enteric-coated formulation is relatively slow
and may be further influenced as a result of delayed gastric
emptying.
Omeprazole is distributed in tissue, particularly gastric
parietal cells. It is highly bound to plasma proteins,
approximately 95% bound to albumin and alpha1-acid
glycoprotein. The onset of action is within one hour and the
time to peak effect is within 2 hours. It has a duration of
action of up to 72 hours or more. In a normal hepatic
function, the plasma half-life is 30 minutes to 1 hour while in
a chronic hepatic disease, the plasma half-life is 3 hours.
Omeprazole is almost completely metabolised in the liver.
The three major metabolites identifiable in plasma are
hydroxyomeprazole, a sulfide derivative and a sulfone.
Omeprazole is subject to an important polymorphism of drug
metabolism as it is a substrate for CYP2C19, the
S-mephenytoin hydroxylase.
Omeprazole is rapidly eliminated, mostly in the
urine as metabolites. Some is excreted in the faeces. The
bioavailability of Omeprazole may be increased in elderly
patients and in patients with impaired hepatic function, but is
not markedly affected in patients with renal impairment.
INDICATIONS
Omeprazole is used in the treatment of gastro-oesophageal
reflux disease; duodenal ulcer, benign gastric ulcer and
Zollinger-Ellison Syndrome. It is also combined with
antibacterial agents in dual or triple therapy regimens for the
elimination of Helicobacter Pylori infection in patients with
duodenal ulcer.
SIDE EFFECTS/ADVERSE REACTIONS
Skin
Skin rash, urticaria and pruritus have been reported, usually
resolving after discontinuation of treatment.
Central and peripheral nervous system
Headache is a common side effect. Dizziness, paraesthesia,
somnolence, insomnia and vertigo are rare. In isolated
cases, reversible mental confusion, agitation, depression
and hallucinations predominantly in severely ill patients have
occurred. Increased sweating, peripheral oedema and
blurred vision have been reported in isolated cases.
Gastrointestinal
Diarrhoea, constipation, nausea, vomiting, flatulence and
abdominal pain.
Hepatic
Rarely increased in liver enzymes. In isolated cases,
encephalopathy in patients with pre-existing severe liver
disease; hepatitis with or without jaundice and hepatic failure
have been reported.
Endocrine
In isolated cases, gynaecomastia has been reported.
Haematological
In isolated cases, leukopenia, thrombocytopenia,
agranulocytosis and pancytopenia have been reported.
Musculoskeletal
In isolated cases, arthralgia, muscular weakness and
myalgia have been reported.
PRECAUTIONS/WARNINGS
Pregnancy
Adequate and well-controlled studies in humans have not
been done. Studies in pregnant rats did not show Omeprazole to have any teratogenic potential at doses 345
times the human dose. Avoid in pregnancy unless there is
no safer alternative.
Breast-feeding
It is not known whether Omeprazole is distributed into
human milk. However, because Omeprazole has been
shown to cause tumourigenic and carcinogenic effects in
animals, a decision should be made on whether breast
feeding should be discontinued or the medication
withdrawn, taking into account the importance of the
Omeprazole to the mother.
Geriatrics
A decreased rate of elimination and an increased
bioavailability are likely to occur in geriatric patients taking Omeprazole.
Gastric Ulcers
Before giving Omeprazole to patients with gastric ulcers, the
possibility of malignancy should be excluded since
Omeprazole may mask symptoms and delay diagnosis.
Hepatic Disease
In chronic hepatic disease, dosage reduction may be
required due to increased half-life.
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