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Codeine Compound
DESCRIPTION
Clean, dry, round, uniform, biconvex, even edged tablets, scored on one side
and white in colour.
Each tablet contains :
Paracetamol BP ................ 500 mg
Codeine Phosphate BP ..... 8 mg
ACTIONS AND MODE OR MECHANISMS OF ACTON
PARACETAMOL
Analgesic - The mechanism of analgesic action has not been fully
determined. Paracetamol may act by inhibiting prostaglandin synthesis in Me
central nervous system and through a peripheral action by blocking
pain-impulse generation. The peripheral actions may also be due to
inhibition of the synthesis of prostaglandins or the synthesis or actions of
other substances, which sensitize pain receptors to mechanical or chemical
stimulation.
Antipyretic - Paracetamol probably produces antipyresis by acting
centrally on the hypothalamic heat-regulating centre to produce peripheral
vasodilation re suiting in increased blood flow through the skin, sweating
and heat loss. The central action probably involves inhibition of
prostaglandin synthesis in the hypothalamus.
CODEINE PHOSPHATE
Analgesic - Binds with stereospecific receptors at many sites within the
central nervous system (CNS) to alter processes affecting both the
perception of pain and the emotional response to pain. Precise sites and
mechanisms of action have not been fully determined, but may partially
involve alterations in release of various neurotransmitters from afferent
nerves sensitive to painful stimuli. It has been proposed that there are
multiple subtypes of opioid receptors. each mediating various therapeutic
and/or side effects of opioid drugs. The actions of an opioid analgesic may
therefore depend upon its binding affinity for each type of receptor and
whether it acts as a full agonist or a partial agonist or is inactive at
each type of receptor. At least two of these types of receptors (mu and
kappa) mediate analgesia. Mu receptors are widely distributed throughout the
CNS, especially in the limbic system (frontal cortex, temporal cortex,
amygdala and hippocampus), thalamus striatum, hypothalamus and midbrain as
well as laminae I, II, IV and V of the dorsal horn in the spinal cord. Kappa
receptors are localized primarily in the spinal cord and in the cerebral
cortex.
A third type of receptor (sigma)
may not mediate analgesia; actions at this receptor may produce the
subjective and psychotomimetic effects, characteristic of opioids, having
mixed agonist/antagonist activity
PHARMACOLOGY
PARACETAMOL : Paracetamol is readily absorbed from the gastrointestinal
tract with peak plasma concentrations occurring about 30 minutes to 2 hours
after ingestion. It is metabolised in the liver and excreted in the urine
mainly as glucuronide and sulphate conjugates. Less than 5% is excreted as
unchanged paracetamol. The elimination half-life vanes from about 1 to 4
hours. Plasma-protein binding is negligible at usual therapeutic
concentrations but increases with increasing concentrations.
A minor hydroxylated metabolite
which is usually produced in very small amounts by mixed-function oxidases
in the liver and which is usually detoxified by conjugation with liver
glutathione, may accumulate following paracetamol overdosage and cause liver
damage.
CODEINE PHOSPHATE : Codeine Phosphate is absorbed from the
gastrointestinal tract and produces peak plasma - codeine concentrations in
about one hour. Codeine is metabolised by O - and N - demethylation in the
liver to morphine and norcodeine. Codeine and its metabolites are excreted
almost entirely by the kidney, mainly as conjugates with glucuronic acid.
The plasma half-life has been reported to be between 3 and 4 hours after
administration by mouth.
INDICATIONS
Codeine Compound Tablet is indicated for the relief of mild to moderate pain
and to reduce fever.
CONTRAINDICATIONS
Patients with known hypersensitivity to any of its components. Diarrhoea
caused by poisoning or pseudomembranous colitis induced by antibiotic. until
toxin materials have been eliminated from G.I.T.
Acute respiratory depression.
SIDE EFFECTS/ADVERSE REACTIONS
PARACETAMOL : Side effects of paracetamol are usually mild, though
haematological reactions have been reported. Skin rashes and other allergic
reactions occur occasionally. Large toxic doses may produce nausea, vomiting
anorexia and abdominal pain.
Liver damage, hepatic failure, coma and death may occur with severe
poisoning.
CODEINE PHOSPHATE : Side-effects may include nausea, vomiting,
constipation, drowsiness and confusion. Micturition may be difficult and
there may be ureteric o r biliary spasm; there is also an antidiuretic
effect. Dry mouth, sweating, facial flushing, vertigo, bradycardia,
palpitations, orthostatic hypotension, restlessness, change of mood, and
miosis may also occur. These effects may occur more commonly in ambulant
patients than those at rest in the bed. Raised intracranial pressure occurs
in some patients.
Following large doses of codeine. excitement and in children, convulsions
may also occur.
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