1. Anesthetics
 Priestly discovered first inhalation anesthetic nitrous oxide
• Loss of sensation
• Insensibility to the vital organs
• Loss of consciousness is reversible
• Temporary insensibility to pain or feeling in the body
Characteristics of anesthetic agent
• Should give enough relaxation time
• Inert, potent, non-flammable, non-irritating
• Should not have toxic effect
• Stable to light and heat
• Economical
• Analgesic action and muscle relaxation
• Should not induce vomiting
• Should not reduce blood pressure
• Should not have any adverse effect with the administration of other drugs.

2. .
Classification of anesthetics
1. General anesthetics
2. Local anesthetics
General anesthetics are further classified into
a. Volatile general anesthetics
b. Non-volatile anesthetics

3. Some of Volatile general anesthetics
Ether
• Anesthetic ether is 96-98% diethyl ether
• Colourless volatile liquid with pungent smell
• Soluble in organic solvents like alcohol, chloroform, etc.
• Prepared by williamson’s synthesis
• Stored in well-closed, light resistant bottles
• Inflammable.
• When exposed in air it forms peroxides or acetic
aldehydes
• Stabilizers like sodium pyrogallate are added
• Stored in internally copper plated containers.

4. Advantages .
• Induces surgical anesthetics without pre- anesthetics medication
• Safe
• Produces muscular relaxation
• Does not modify blood pressure
• Economical and stable
• Administered without a complicated process
Disadvantages
• Induction is slow
• Boils at low temperature
• Inflammable
• Vapours are irritating to mucous membrane
• Nausea and vomiting appear
• Slow recovery
• Ether convulsions may occur in children

5. Derivatives of ether were found to be less irritating than
.
ether
Methyl-n-propyl ether
• Powerful than ethyl ether
• Less adverse side effects
Vinyl ether
• Colourless liquid
• Miscible with alcohol, ether and chloroform
• Stored in well closed container
• Stored in cool, dark place
Advantages
• More potent
• Speedy recovery
• Useful in Dental procedures
• Used in minor operations for short duration
Disadvantages
• Damages liver
• Inflammable

6. Chloroform
.
• Powerful volatile liquid
• Prepared from bleaching powder and ethyl alcohol
• Colourless volatile liquid
• 1-2% of ethanol is added to prevent the formation of
poisonous phosgene gas
• Should be protected from light
Advantages
• Induction is prompt
• Vapours are not flammable
• Used in obstetrical anesthetics
Disadvantages
• Toxic
• Liver and cardiac toxicity
• Due to its toxicity chloroform is no longer used

7. .
Halothane
• Fluorinated volatile liquid
• Structure similar to chloroform
• Heavy colourless liquid
• Non-flammable
• Sweet fruity odour
• Miscible with chloroform, ether, etc.
• Stored in air tight containers at low temperature
• Should be protected from light
• Stable in presence of alkalis

8. Advantages .
• Not flammable
• Does not irritate the respiratory passage
• Nice pleasant odour
• Potent anesthetics
• Post operative vomiting is low
• Relaxes bronchial muscle
• Safe
• Used as anesthetic during plastic surgery
Disadvantages
• Causes cardiovascular depression
• Depresses respiration
• Poor analgesic
• Expensive
• Has to be given through a special apparatus
• Hepatic damage
• Used for intro-abdominal operation

9. Trichloroethylene
.
• Colourless
• Characteristic odour
• Thymol is added as preservative
• Immiscible in water
• Miscible with alcohol, chloroform, ether, etc
• Stored in air tight and light resistant containers
• Kept in cool places
Advantages
• Potent
• Rapid onset of action
• Recommended for short procedures such as dental extractions, etc.
• Used for migraine pain, angina pectoris and child birth
Disadvantages
• Poor muscular relaxation
• May be hepatotoxic and tachypnoea
• Breaks down in the presence of soda lime to give highly toxic products

10. .
Ethyl chloride
• Non- irritating
• Highly volatile
• Inflammable
• At ordinary temperature and pressure it is a gas
• Pleasant characteristic odour
• Miscible with organic solvents like alcohol and ether
• Slightly miscible in water
• Stored in air tight containers
• When sprayed on skin it evaporates rapidly and cools the skin

11. .
Advantages
• Used as local anesthetic for minor operations such as incision, etc
• As general anesthetic it induces anesthetic within 1 or 2 minutes
• Quick induction
Disadvantages
• May damage liver
• Induce cardiac arrhythmias or cardiac arrest
• Poor muscle relaxation
• Low safety
• Difficult to maintain steady depth of anesthetic

12. .
Nitrous oxide
• Colourless inorganic, non-irritating
• Sweet taste
• Non-flammable
• Available in steel cylinders
• Known as laughing gas
Advantages
• Safest anesthetic
• Non-flammable
• Non-irritating
• Rapid induction nad rapid recovery
• Pronounced analgesic action
• Does not induce post-operative nausea and vomiting
• Used in painful procedures like cleaning and changing burn wounds
Disadvantages
• Not potent anesthetic
• Pre-anesthetic medication has to be given
• Produce violent excitation
• Hypoxia
• Increases cardiac irregularities

13. .
Cyclopropane
• Colorless sweet smelling gas
• Available in metal cylinders in compressed form
• Kept in cool place
Advantages
• Potent anesthetic
• Has fast induction
• Rapid and smooth recovery
• Maintains blood pressure and cardiac contracitility
• Used in hemorrhagic agent
• Does not produce irritation of respiratory passage
• Good muscle relaxant
• Produces quite breathing
• Supplies enough oxygen
• Does not produce visceral damage

14. .
Disadvantages
• Induction is done carefully
• Produce cardiac irregularities
• Depresses respiratory center
• Increases capillary oozing
• Anesthetic mixture of cyclopropane and oxygen is explosive

15. Non-volatile anesthetics
Thiopental sodium
• Yellowish white hygroscopic powder
• Characteristic odour and bitter taste
• Soluble in water
• Solution is freshly prepared before using it in injection form
• Stored in sealed containers
• It is a derivative of barbituric acid and malonic ester
• Patient passes through the stages of hypnosis and deep sleep to
anesthesia
• First consciousness is lost and then reflex activity and finally
medullary centres are lost.
• Used in minor operations such as fracture, dental surgerics, etc
• Anti-convulsant

16. .
Advantages
• Non-explosive
• Easy to administer
• Induction is rapid and without any unpleasant feeling
• Tendency of nausea and vomiting is very less
• Does not effect respiration
• No post-anesthetic complications
Disadvantages
• Needs constant supervision to avoid overdostage
• Depresses vasomotor centre and myocardium
• Poor analgesic
• Does not produce muscular relaxation

17. Local anesthetics
Characteristics of local anesthetics
• Non-irritant
• Should not be painful
• Low toxicity
• Stable
• Should not damage nerve cells
• Sterilization of drugs should be easy
• Should not damage nerve cells

18. The Esters
Cocaine
• It is alkaloid obtained from leaces of Erthroxylon Coca
• It is methyl benzoyl ester of Ecgonine which is a tropane derivative
• Basic in nature
• Levorotatory
• White Crystalline powder
• Sparingly soluble in water
• Hygroscopic in nature
Advantages
• Useful in surgery of nose, throat and eye
• Local anaesthtic action
• Stimulates central nervous system
Disadvantages
• Drug is addiction
• Dilates pupil
• Raises blood pressure
• Produces euphoria and fatigue
• Poisonous in nature

19. .
Benzocaine
• Ester derivative
• White crystalline powder
• Stored in air tight containers
• Light resistant containers
• Soluble in water
• Low toxicity
• Available under the name anesthetic
• Useful as dusting
• Used in throat lozenges
• Useful in relieving pain of gastric ulcer
• Used in ointment form and is a surface anesthetic

20. The amides
Lignocaine
• Crystalline solid
• Sparingly soluble in water
• Used as hydrochloric salt
• Very stable
• Stored in room temperature
• Resistance to hydrolysis
• Used topically as surface anesthetic and ointment
• Available in injection form as spinal nerve block injections
• Quick onset of action
• Good analgesic agent
• Used for dental analgesia
• Used in cardiac arrhythmias
• Used for patients who are allergic to procaine
• Toxicity is similar to that of other local anesthetics
• May cause drowsiness