|
Drug Information
Pharmacokinetics
| Indication
& Dosage | Action
| Interactions
Adverse
Effect & Precautions |
Brands available in Market
Pharmacokinetics
Lignocaine is readily absorbed
from the gastrointestinal tract, from mucous membranes, and through
damaged skin. Absorption through intact skin is poor. It is rapidly
absorbed from injection sites including muscle.
After an intravenous dose lignocaine is rapidly and widely distributed
into highly perfused tissues followed by redistribution into skeletal
muscle and adipose tissue. Lignocaine is bound to plasma proteins,
including alpha(1)-acid glycoprotein (AAG). The extent of binding is
variable but is approximately 66%. Plasma protein binding of lignocaine
depends in part on the concentrations of both lignocaine and AAG. Any
alteration in the concentration of AAG can greatly affect plasma
concentrations of lignocaine
Plasma
concentrations decline rapidly after an intravenous dose with an initial
half-life of less than 30 minutes; the elimination half-life is 1 to 2
hours but may be prolonged if infusions are given for longer than 24
hours or if hepatic blood flow is reduced.
Lignocaine is largely metabolised in the liver and any alteration in
liver function or hepatic blood flow can have a significant effect on
its pharmacokinetics and dosage requirements. First-pass metabolism is
extensive and bioavailability is about 35% after oral administration.
Metabolism in the liver is rapid and approximately 90% of a given dose
is dealkylated to form monoethylglycinexylidide (MEGX) and
glycinexylidide (GX). Both of these metabolites may contribute to the
therapeutic and toxic effects of lignocaine and since their half-lives
are longer than that of lignocaine, accumulation, particularly of
glycinexylidide, may occur during prolonged infusions. Further
metabolism occurs and metabolites are excreted in the urine with less
than 10% of unchanged lignocaine. Reduced clearance of lignocaine has
been found in patients with heart failure, alcoholic liver disease, or
chronic or viral hepatitis. Concomitant therapy with drugs that alter
hepatic blood flow or induce drug-metabolising microsomal enzymes can
also affect the clearance of lignocaine. Renal impairment does not
affect the clearance of lignocaine but accumulation of its active
metabolites can occur and may lead to toxicity. Lignocaine
crosses the placenta and blood-brain barrier; it is distributed into
breast milk.
Indication
& Dosage
INFILTRATION
ANAESTHESIA, SURFACE ANAESTHESIA, NERVE BLOCK, EPIDURAL ANAESTHESIA, IV
TOPICALLY TO FACTILITATE ENDOTRACHEAL INTUBATION, OTOLOGICALM RECTAL AND
VAGINAL EXAMINATION, URETHRAL EXAMINATION, URETHRAL PROCEDURES,
CATHETERISTATION, CYSTOSCOPY, BRONCHOSCOPY, PAINFUL CYSTITIS, PAIN AND
ITCHING DUE TO MINOR BURNS, INSECT BITES, HAEMORRHOIDS AND ANAL FISSURES:
(1-5% strength prepns.) Dosage depends on several factors such route, type
and extent of surgical procedures, duration of anaeshtesia and patients’
condition and age. During infiltration use, max lognocaine dose should not
exceed 200mg. see lit.
It is a local anaesthetic which stabillises the neuronal membrane and inhibits the ion movements which are necessary for conduction of impulses. In the heart lignocaine reduces phase 4 depolarisation, decreases automaticity. Duration of action potential and effective recactory period is reduced.
Propranolol: Increased lidocaine levels
resulting in toxicity.
Cimetidine: Decreased lidocaine clearance with possible toxicity.
Procainamide: Additive cardidepressant action may occur with
potential for conduction abnormalities.
Tocainide: Increased incidence of adverse reactions.
Adrenaline: Reduces the absorption of lidocaine.
Adverse
Effect & Precautions
Convulsion,
tremor, dizziness, blurred vision, nervousness, nausea and
respiratory arrest. Cardiovascular collapse and cardiac arrest.
Symptoms may occur quickly, without warning.
Precaution: Resuscitation facilities should be avilable when local
anaesthesia is being given. Bradycardia. Hepatic and renal
dysfunction.
Pregnancy: May be used.
Breast Feeding: Use with caution.
Man: May be used.
21.30mg/ml
