1. ANAESTHETICS

1.1.      General  Anaesthetics

KETAMINE

General   Information 

Drug Code                            Preparation                                                Strength

            120                              Inj.  Ketamine  HCL                                    50 mg / vial

            313                              Inj.  Ketamine  HCL                                    10 mg / vial 

Description of the Drug

 

              Ketamine is a phencyclidine derivative used as an I.V. anaesthetic.  It casuses dissociative     

              anaesthesia (catatonia + amnesia + analgesia)

 

Mode of Action

It depresses the central nervous system by blocking the effects of the excitatory neurotransmitter, glutamic acid at the NMDA receptors.  It is a cardiovascular stimulant, causing an increase in B.P, heart rate and cardic output due to sympathetic stimulation.  It increases cerebral blood flow.

 

Pharmacokinetics

On I.V. administration, it crosses the blood brain barrier and reaches effective concentration in the brain rapidly.  Onset of action is 1-3 minutes.  Duration of analgesia is 40 minutes.  Duration of anaesthesia is 15 minutes.  Duration of amnesia is 1-2 hours.  It is subsequently redistributed to other tissues.  It is metabolized in the liver and is excreted in urine and bile.

Clinical  Information 

Indications

·For indication of anesthesia.

·To provide analgesia for painful procedures of short duration. 

Dosage

·I.V.  – 1-2 mg/kg.

·I.M.  – 5-10 mg/kg.

·Continuous infusion  - 5-20 microgram/kg/min. 

Routes of Administration   I.V.,  I.M.,  Continuous infusion.

 

Contraindications

·Patients with hypertension, ischaemic heart disease, aneurysms and hyperthyroidism (due to CVS stimulation).

·Patients with increased  intracranial tension and psychotic disorders. 

Precautions / Practice points

·It can be used with advantage in patients with hypovolemia and shock.

·Administration Instructions:

-  Hive intravenous injections very slowly, not exceeding a Concentratim of 2mg/ml and rate not exceeding 0.5 mg/kg/min.

-  Do not mix with barbiturates and diazepam in the same syringe.

-  Always monitor the heart rate, B.P. respiratory rate and oxygen saturation 

Drug Interactions

Barbiturates and narcotics may prolong the recovery time. 

Adverse Effects

Common effects:

Emergence phenomena during recovery from ketamine are common vivid, often unpleasant dreams, confusion, hallucinations, delirium, involuntary movement.  Diazepam 0.2-0.3 mg/kg intravenously before giving ketamine reduces the incidence of these effects.

Rare Effects:

Increase in skeletal muscle tone and fasciculations. 

Drug Toxicity

Increased cardiac stimulation, arrhythmias and respiratory depression. 

Treatment of Toxicity

Ventilatory support,  CVS monitoring and symptomatic treatment. 

Storage

Store in airtight containers. 

Shelf Life                    2 Years 

THIOPENTONE SODIUM 

General  Information 

Drug Code                      Preparation                                              Strength

        121                          Inj. Thiopentone Sodium                            500 mg 

Description of the Drug

It is an ultra short acting Thiro barbiturate. 

Mode of Action

It acts via the GABA receptors in the brain to decrease neuronal activity, rate of firing and synaptic transmission.  It produces loss of consciousness and anaesthesia.  It also reduces the arterial blood pressure, stroke volume and cardiac output. Cerebral blood flow is de
creased and hence it is safe to use in increased intracranial tension. 

Pharmacokinetics

It is highly lipid soluble and on IV administration, reaches effective blood concentration rapidly.  Hence, onset of action is immediate (10-20 seconds).  It is then redistributed to muscle, fat and solid organs.  Hence, it is short acting (loss of consciousness lasts for only 10-15 minutes).  It is metabolized in liver and is excreted by the kidney. 

Clinical Information 

Indications

·Induction of general anesthesia .

·Can be used alone for providing anesthesia for minor surgical procedures of short duration.

·Adjunct  for intubation in head injury patients.

·Control of convulsive states.

·Treatment of elevated intracranial pressure. 

Dosage

Adult

3-5 mg/kg as 2.5% solution 

Children

5-6 mg/kg 

Route of Administration    IV. 

Contraindications

Thiopentone sodium is contraindicated inpatients with porphyria as it can precipitate

attacks. 

Precaution  / Practice points

·Poor analgesic and muscle relaxant.  Hence, for adequate relaxation, a muscle relaxant should be used and analgesics should be given for postoperative pain.

·Use with caution in patients with hepatic and renal dysfunction.  (For dose adjustments, see appendix)

·Cumulative toxicity can occur, so avoid repeated dosing.

·Administration Instructions:

-  Thiopentone is incompatible with the following drugs and MUST NOT be mixed with succinylcholine, atropine, amikacin, dimenhydrinate,diphenhydramine, codeine,morphine, pethidine, insulin, metaraminol, norepinephrine, penicilline G,

-  Always monitor the respiratory rate, heart rate and B.P. while administration.

- Make sure administration is into the vein.  Any intra-arterial injection or extravasation may produce intense vasoconstriction causing pain, gangrene

and necrosis of limb. 

Drug Interactions

Increases the CNS depressant effects of narcotic analgesics.

Adverse Effects

·Laryngospasm may occur if respiratory secretions are present during induction.  Preoperative atropine should be given to decrease secretions.

·Gastro-intestinal cramps.

  • Pain on IM injection.

 

Drug Toxicity

Respiratory depression, severe hypotension and cardio vascular collapse may occur.

Treatment of Toxicity

Continuous CVS monitoring, correction of hypovolemia with IV fluids, measures to combat shock - pressors such as norepinephrine and putting the patient in Trendelenburg’s position.

Storage

Protect from Light.

Shelf Life              3 years.

HALOTHANE

General Information

Drug Code                                    Preparation                         Strength

        125                                        Halothane                              200 ml

Description of the Drug

Halothane is a volatile inhalational anaesthetic agent.  It is a clear, colourless, noninflammable, nonirritant liquid.

Mode of Action

Halothane decreases the rate of firing and neuronal activity in the brain by altering the

lipid layer of cell membranes, causing structural alterations in ion channels.  This results in depression of CNS and anaesthesia.  It depresses the respiratory center and is also a bronchodilator.  It is a cardiac depressant and causes a decrease in cardiac output and heart rate.  Also causes peripheral vasodilatation and hypotension.  It sensitizes the myocardium to the effects of catecholamines.  It increases cerebral blood flow and raises intracranial and CSF pressures.

Pharmacokinetics

It is absorbed by inhalation and being lipid soluble crosses the blood brain barrier.  It is POTENT anaesthetic and minimum alveolar concentration is 0.75% to produce its effects.  Excreted mainly by exhalation, though some detoxitication may occur in the liver. 

Clinical Information 

Indications

For induction and maintenance of general anaesthesia. 

Dosage

·  Inductions of anaesthesia:

·  2 to 4% v/v of halothane in oxygen or mixture of nitrous oxide and oxygen.

·  Maintenance of anaesthesia 0.5% to 1.5% v/v.

Routes of Administration

Inhalation  -nasal or endotracheal intubation.

Contraindications

·  History of unexplained jaundice following previous exposure to halothane.

·  Patients who have developed malignant hyperthermia with prior use.

·  Patients with increased intracranial pressure.

Precaution  / Practice points

·  Halothane does not produce adequate analgesia and muscle relaxation.

·  Advantage of halothane are:

·  Induction and recovery is quick and pleasant with halothane.

·  Vapour is nonirritant and incidence of coughing or breath holding is less.

·  Not recommednded for obstetrical anaesthesia as it is a potent uterine muscle relaxant and may cause postpartum haemorrhage.,

Durg Interactions

Potentially fatal:

·  Catecholamine like adrenaline, theophylline, MAO inhibitors and tricyclic antidepressants should be avoided with halothane due to the risk of causing hypotehsive effects with betablockers, calcium channel blockersa and other antihypertensives and antipsychotics.

·  Risk of hepatotoxicity increased by INH and other hepatotoxic drugs

Nonfatal:

·  The effects of competitive muscle relaxants like d-tubocurarine are enhanced by halothane.

Adverse Effects

·  Most significant adverse effects is hepatotoxicity.  It can be mild,self limiting hepatic dysfunction, characterized by elevated serum SGOT and SGPT or a severe acute fulminant hepatitis.

·  In susceptible individuals halothane may tigger off a syndrome of malignant hyperthermia – tachycardia, tachypnoea, pyrexia, acidosis, arrhythmias, cyanosis, muscular rigidity and unstable blood pressure.  Hyperkalemia may occur.  Treatment consists of external cooling measures like icepacks,  ventilatory support, CVS monitoring, correction of arrhythmias and blood pressure, maintenance of fluid and electrolyte balance.

Durg Toxicity

Severe bradycardia, profound hypotension, respiratory depression and cardiac arrest may occur.

Treatment of Toxicity

Withdrawal of drug, ventilatory support with oxygen administration, maintenance of  B.P.., fluid and electrolyte balance.

Storage

Below 25o C in airtight containers. Protect from light.

Shelf Life               5 years.

ISOFLURANE

General  Information 

Drug Code                                                 Preparation                                             

              490                                                       Isoflurane

Description of the Drug

Isoflurane is a halogenated volatile anaesthetic. It is an isomer of enflurane. It is nonirritant and non-inflammable.  Its advantage over other inhalational anaesthetics are it is more potent, induction and recovery from anaesthesia is pleasant and there is less postoperative nausea and vomiting.

Mode of Action

General anaesthetics act by fluidizing the cell membrane and decreasing or altering the stucture of ion channels in the membrane, thereby decreasing the firing rate and potentials.  Synaptic transmission is also decreased.  It causes a decrease in arterial pressure and hypotension, but heart rate is increased.  It also does not sensitize the myocardium to circulating catecholamines.  It causes respiratory depression.

Pharmacokinetics

It is absorbed by inhalation and only 0.2% is metabolized to inorganic Fluoride.  Excretion is mainly by exhalation.  Its minimum alveolar concentration is 1.2%.

Clinical  Information.

Indications

Induction and maintenance of general anaesthesia.

Dosage

·  For induction: Starting with 0.5% upto 3%, given mixed with oxygen alone or mixture of nitrous oxide and oxygen.

·  For maintenance: 1.5 – 2.5%.

Routes of Administration IV.

Inhalation only  - nasal or endotracheal intubation.

Contraindications

·  Patients known to have malignant hyperpyrexia.

·  Patients with increased intracranial pressure, as isoflurane increases the intracranial pressure.

Precaution  / Practice points

·  Usually used only in maintenance, induction being done by an intravenous induction agent.

·  Analgesic and muscle relaxant is necessary.

·  When compared to halothane it has a higher incidence of coughing, laryngospasm  (due to its pungency) but less tendency to cause cardiac depression and arrhythmias.  It also does not sensitize the heart to circulating catecholamines like halothane.

Drug Interactions

Enhancement of action of competitive muscle relaxants like d-tubocurarine.

Adverse Effects.

Common Effects:

·  Coughing, laryngospasm, salivation, etc., during induction.

·  Increases intracranial pressure.

Rare Effects :

·  In susceptible individuals, malignant hyperpyrexia can occur.

Drug Toxicity

Hypotension, cardiac and respiratory arrest may occur.

Treatment of Toxicity

Withdrawal of the drug, CVS monitoring, ventilatory support and maintenance of B.P.

Storage

It is volatile hence, store in airtight containers away from light.

Shelf Life              4 years.