|
Normaten
Atenolol 50 / 100mg
Composition
Normaten Tablets 50mg : Each tablet contains Atenolol 50mg and Titanium
dioxide 0.5% as colourant.
Normaten Tablets 100mg . Each tablet contains Atenolol 100mg. Contains
Sunset Yellow 0.34% and Titanium Dioxide 1.00% as colourants.
Properties
Atenolol is a hydrophilic β1-adrenoceptor blocking drug with general
properties similar to those of propranolol. It reduces cardiac activity by
diminishing or preventing sympathetic β-adrenoceptor stimulation. It
reduces the rate and force of contraction of the heart and decreases the
rate of conduction of impulses through the conducting system. Its principal
effect is to reduce the response of the heart to stress and exercise and it
reduces blood pressure in patients with hypertension. Atenolol is classified
as cardioselective and is reported to lack intrinsic sympathomimetic
activity and membrane stabilising properties.
Atenolol is incompletely absorbed from the gastrointestinal tract and is not
significantly metabolised. It is excreted in the urine and its biological
half-life is longer than would be anticipated from its plasma half-life of
about 6 - 7 hours. Atenolol diffuses across the placenta and is excreted in
breast milk. Only small amounts are reported to cross the blood brain
barrier, and it is only about 5 % bound to plasma protein.
Indications
Normaten is indicated for the control of hypertension and management of
angina pectoris. It is also used as oral maintenance therapy for cardiac dysrhythmias after the acute attacks has been controlled by intravenous
therapy and for long-term prophylaxis of myocardial infarction after
recovery.
Dosage and Administration
In adult and children over 12 years :
Hypertension : 50 to 100mg daily as a single dose. The effects will be fully
established after 1 to 2 weeks. A further reduction in blood pressure may be
achieved by combining Atenolol with other antihypertensive agents.
Angina :
50mg twice daily or 100mg daily once. It is unlikely that the higher dose
would be additionally beneficial.
Dysrhythmias : Initially controlled
intravenously. Oral maintenance dosage of 50 - 100mg daily, given as a
single dose.
Myocardial infarction : In suitable patients, Initially
controlled intravenously, followed by 50mg Normaten orally, 15 minutes after
the intravenous dose, provided no adverse effects occur. This should be
followed by a further 50mg orally 12 hours later, then 24 hours later by
100mg orally to be given once daily for up to 10 days. If bradycardia and/or
hypotension, or other adverse effects occur, requiring treatment, Normaten
should be discontinued.
The elderly : Dosage requirements may be reduced,
especially in patients with impaired renal function.
Children : There is no paediatric experience with Atenolol. Atenolol is not recommended for use in
children under 12 years of age.
Dosage should be adjusted in patients with severe impairment of renal
function as Atenolol is excreted via kidneys.
| Creatinine clearance: |
Dosage: |
| >35ml/min/1.73 m2 |
no adjustment required |
| 15 - 35ml/min/1.73 m2 |
50mg daily or 100mg once every two days |
| <15ml/min/1.73 m2 |
50mg on alternate days or 100mg once every four days |
Contraindications
It is contraindicated in patients with bronchospasm or obstructive airways
disease, metabolic acidosis, sinus bradycardia, or partial heart block
(second or third degree heart block). It should not be used in patients with
cardiogenic shock and in overt heart failure.
Precautions
Atenolol should not be given to patients with phaeochromocytoma without
concomitant α-adrenoceptor blocking therapy. Use with caution in
pregnancy, during breast feeding, in patients with inadequate cardiac
function, diabetes mellitus or hyperthyroidism.
Avoid abrupt withdrawal especially in patients with coronary artery disease,
since it may exacerbate angina or precipitate myocardial infarction. Reduce
dose may be required in patients with renal failure.
Special care should be taken with patients whose cardiac reserve is poor.
β-adrenoreceptor blockers should be avoided in overt heart failure.
However, they may be used in patients whose signs of failure have been
controlled.
One of the pharmacological actions of Normaten is to reduce heart rate. In
rare instances when symptoms may be attributable to the slow heart rate, the
dose may be reduced. Normaten modifies the tachycardia of hypoglycaemia.
Although cardioselective (β1) β-blockers may have less effect on lung
function than non-selective β-blockers, as with all β-blockers, these
should be avoided in patients with reversible obstructive airways disease,
unless there are compelling clinical reasons for their use. Where such
reason exist, Normaten may be used with caution. Occasionally, some increase
in airway resistance may occur in asthmatic patients, however, and this may
usually be reversed by commonly used of bronchodilators such as salbutamol
or isoprenaline.
In patients suffering from ischaemic heart disease, as with other
β-blocking agents, treatment should not be discontinued abruptly.
Anaesthesia : Care should be taken when using anaesthetic agents with
Normaten. The anaesthetist should be informed and the choice of anaesthetic
should be the agent with as little negative inotropic activity as possible.
See also section under Drug Interactions below.
Drug Interactions
Normaten may enhance the effects of other myocardial depressant including
anti-arrhythmics such as quinidine, procainamide, lignocaine, phenytoin and
verapamil. The effects of Atenolol may be diminished by isoprenaline and may
be enhanced by guanethidine, bethanidine, reserpine, and diuretics. Its
peripheral vasoconstrictor effects may be enhanced by noradrenaline and
adrenaline.
Caution should be exercised when transferring patients from clonidine to
β-adrenoreceptor blocking drugs. If β-adrenoreceptor blocking drugs
and clonidine are given concurrently, clonidine should riot be discontinued
until several days after the withdrawal of the β-adrenoreceptor blocking
drugs (see also prescribing information on clonidine)
Care should be exercised in prescribing β-adrenoreceptor blocking drug with Class 1
antidysrhythmic agents such as disopyramide.
β-adrenoreceptor blocking drugs should be used with caution in combination
with verapamil in patients with impaired ventricular function. The
combination should not be given to patients with conduction abnormalities.
Neither drug should be administered intravenously with 48 hours of
discontinuing the other.
Incompatibilities
None known.
Side Effects
Atenolol shares the toxic potentials of β-adrenergic blocking agents. In
therapeutic dosage, it is well tolerated and has low incidence of adverse
effects.
Cardiovascular Effects : Potentially serious adverse cardiovascular effects
of atenolol include bradycardia; profound hypotension; second of
third-degree atrioventricular (AV) block; and precipitation of severe
congestive heart failure (CHF), which is likely to occur in patients with
pre-existing left ventricular dysfunction. Other adverse cardiovascular
effects include coldness of the extremities and postural hypotension.
Central Nervous System Effects : Dizziness, fatigue, and mental depression
are the most common CNS effects of atenolol. Less common effects are
lethargy, drowsiness, unusual dreams, light-headedness and vertigo. Other
effects that may occur include visual disturbances, hallucinations,
disorientation, short-term memory impairment, emotional lability, catatonia
and impaired performance on neuropsychometric tests.
Gastrointestinal Effects : Adverse GI reactions include diarrhoea, nausea
and vomiting.
Other Adverse Effects : The possibility of other adverse effects associated
with other β-adrenergic blocking agents that may occur include haematologic
reactions (eg. agranulocytosis, nonthrombocytopenic or thrombocytopenic
purpura); allergic reactions characterised by fever, sore throat
laryngospasm, and respiratory distress; reversible alopecia; Peyronie's
disease; Raynaud's phenomenon; erythematous rash; and impotence.
Overdosage and Treatment
In the event of severe overdosage, hospital admission is strongly advised.
Symptoms of overdosage may include severe reactions of the side effects. If
the overdosage is recent, stomach should be emptied by gastric lavage.
Severe bradycardia and hypotension may response to atropine 1-2mg
intravenously. Where response is inadequate, a bolus dose of 5-10mg glucagon may be given intravenously, followed if necessary by an I.V.
infusion of glucagon 1-5 mg/hour depending to response. The rate of
infusion should be reduced as the patient improves. Dobutamine or
isoprenaline have also been used in the management of hypotension. I.V.
aminophylline, or inhaled or I.V. salbutamol, may be of benefit where
bronchospasm occurs. Other supportive and symptomatic treatment should be
given.
Shelf-life
4 years from the date of manufacture.
Presentation
Normaten Tablets 50mg : White, round, coated tablets in 28's blister
calendar packs of 14's.
Normaten Tablets 100mg : Orange, round, coated
tablets in 28's blister packs of 7's.
Storage
Protect from light and moisture. Store below 30°C. |
