Pharmacology for Dentistry

62 Section 2/ Drugs Acting on CNS

20 to 25 percent is required to produce surgi-
cal anaesthesia. It has a low blood solubility.
The induction and recovery are rapid and
smooth. Blood pressure and cardiac contrac-
tility are well maintained with cyclopropane
even on prolonged administration. Muscle
relaxant activity is fairly good. Because of its
highly inflammable and explosive nature, the
close circuit has to be used to conserve the
drug and to keep its concentration in the op-
erating room low.

Because of its smooth induction and
non-irritant to the respiratory passage, the
danger of overdosage must be watched for.
Cyclopropane also sensitizes the myocar-

dium to adrenaline and may produce a va-

riety of cardiac irregularities such as tachy-

cardia and fibrillation. That is the reason for

avoiding cyclopropane anaesthesia in pheo-

chromocytoma and thyrotoxicosis. Cyclo-

propane shock (in patients with sepsis) is

another drawback, which produces a sud-

den fall of blood pressure with collapse.

VOLATILE LIQUIDS

ETHER (DIETHYL ETHER)

It is a colourless, volatile liquid with a pun-

gent odour and produces irritating vapours

which are inflammable and explosive. It is

Table 2.1.1: Classification of general anaesthetics.

I. Inhalational anaesthetics

i. Gases

Nitrous oxide 70-80% with other agents

Cyclopropane 5-25%

ii. Volatile liquids

Ether (Diethyl ether) 3-10%

Trichloroethylene (TRILENE) 0.25-0.75%

Halothane (FLUOTHANE) 0.5-2.0%

Methoxyflurane (PENTHRANE) 0.1-0.3%

Enflurane (ETHRANE) 1-3.0%

Isoflurane (FORANE) 0.8-2.0%

II. Intravenous anaesthetics

i. Ultra short acting barbiturates

Hexobarbitone (sodium salt)

Thiopentone sodium 3-5 mg/kg as 2.5% solution

Methohexitone sodium (BREVITAL) 1-3 mg/kg as 1% solution

ii. Non-barbiturate intravenous anaesthetics

Propanidid (EPONTOL) 5-10 mg/kg as 5% solution

Ketamine (KETMIN) 2 mg/kg IV, 6.5-13 mg/kg IM

Droperidol (INNOVER) + Fentanyl Droperidol 2.5 mg + fentanyl 0.05 mg/ml; 4-6

ml is diluted in glucose solution and infused

over 10 min

Diazepam (CALMPOSE) 0.2-0.4 mg/kg slow IV

Lorazepam (ATIVAN) 0.05-0.1 mg/kg slow IV

Midazolam 0.05-0.1 mg/kg slow IV