The document details various pharmacological agents acting on the central nervous system, focusing on general anesthetics and their stages, namely analgesia, excitation, surgical anesthesia, and medullary paralysis. It describes specific anesthetic agents such as diethyl ether, halothane, chloroform, nitrous oxide, and cyclopropane, covering their physical properties, pharmacological actions, advantages, disadvantages, and therapeutic uses. Additionally, it discusses intravenous anesthetics like thiopentone, and the purpose of preanesthetic medication to enhance anesthesia safety and effectiveness.

1. Drug Acting on Central
nervous System
Compiled By : SWATI G. PATIL
M. Pharm
Pharmaceutics

2. General Anesthetics
These are the pharmacological agent which
when administered externally , bring loss of
all five modalities of sensation with reversible
loss of consciousness.
1. Light
2. Sound
3. Taste
4. Temperature/
Pressure
5. Smell

3. Stages of general anesthesia
1. Stage of analgesia & Amnesia
2. Stage of delirium or excitement
3. Stage of anesthesia chirurgical
(anesthesia for surgery)
4. Stage of medullary paralysis respirations
(intoxication, respiratory arrest)

4. I. stage of Analgesia &
Amnesia
• This stage is in between induction of
anesthesia to the loss consciousness.
• Pain is progressively abolished during this
stage .
• Patient remains conscious can hear and see
and feel dream like state .
• All reflexes are present and respiration is
normal .
• It difficult to maintain –used to short
procedure only .
• Suitable for dental surgery & obstetrical
Procedure . Like Burn And Small Stitching.

5. II. Stage of Excitation
• From the loss of consciousness to beginning of regular
respiration.
• Excitement and patient may shout , struggle and hold his
breath .
• Muscle tone increase and jaw are slightly closed.
• Breathing is jerky , vomiting and involuntary micturition or
defecation may occur.
• Heart rate and B.P. may rise and pupil dilate may
sympathetic stimulation .
• No stimulus or operative procedure carried out during this
stage.
• Breathing are commonly seen , potentially dangerous
response can occur during this stage including vomiting ,
laryngospasm, uncontrolled movement.
• This stage can found in modern anaesthesia, preanaesthetic
medication ,rapid induction.

6. III. Stage of Anesthesia Chirurgical
(surgery)
• Extend from onset of regular respiration to
cessation of spontaneous berating . This has been
divide into four plane.
Plane 1 : Roving eye ball. This plane ends when eye
become fixed.
Plane 2 : Loss of corneal and pharyngeal reflexes.
Plane 3 : Pupil start dilate and light reflex is lost .
Plane 4 : Intercostal paralysis , shallow abdominal
respiration , pupil are dilated
Dilate pupil
Normal pupil

7. IV. Stage of Medullary Paralysis :
• It is stage of overdose beyond the stage of surgical
anaesthetisia in which medullary centers completely
paralyzed.
• It is characterized by stoppage of breathing , fall of blood
pressure to the zero level and cardiovascular collapse. It
leads to death.
• Vigorous and prompt measure only , can save the patient
from this passage .
DEATH

8. (A)Volatile or
Inhalatory anasthetics
1. Liquids :
# Diethyl Ether
# Chloroform
# Halothane
# Methoxy flurane
# Trichloro
ethylene
2. Gases :
# Cyclopropane
# Nitrus oxide
B) Non volatile /
Intravenous
Anaesthetics
1.Barbiturates
# Thiopentone
# Kemithal
# Methohexital
2. Nonbarbiturates
# Propenamide
# Ketamine
# Etomide

9. Pharmacology of drug
# Diethyl Ether :
Physical Properties :
• Colourless ,volatile liq. With pungent odour.
• Boil at 350 C , vapor irritant.
• Exposed in air , moisture or light , it get convert to ether
peroxide and acetic aldehyde , which is irritant in nature
• Highly explosive.
• Stored in umber colour glass bottle covered with black paper.
• 10-15 % in inspired air is sufficient for induction of anaesthesia
which can be maintained but 4-5 % concentration.

10. Pharmacological Action
• Only a major portion of ether is oxidized in the
body and is eliminated through the lungs .
• The miscibility of drug with body fluid requires
large amount of drug for induction of anesthesia
and induction is slow.
• Ether irritate the respiratory track and enhance the
mucosal secretion.
• Drug may causes laryngospasm ,Ether is also
known to increase heart rate, blood pressure and
blood sugar. It also causes peripheral vasodilation .
Ether depresses myocardial contractility.

11. Advt / Therapeutic effect :
• Safest agent in wide margine , also unexperienced hand.
90 mg/100 ml blood Indused anaesthesia
190 mg/100 ml bloodCauses respiratory Track
• Not only safe anaesthetics but good analgesic also.
• It does not interfere with uterine contractility.
• Does not have any effect on liver , kidney , and heat.
• No special or complicated apparatus if required.
• Eeconomical agent .

12. Dis- advt / Adverse effect :
• Induction is very slow and stormy.
• Ether vapor are irritant and may increase salivary , bronchial
secretions
• Ether is highly explosive , hence cannot be used for
cauterization.
• Recovery is slow and is associate with high incidence of
nausea and vomiting .
• In children , it may produced convulsion .
• Used As general anaesthetics
• Used As Rubifacient
• Used as solvent
• Used As cleasing
agent
Convulsion

13. Dose :
• 1 – 4 ml
• For induction anaesthesia :
upto 15 % in inspired air
Maintainance of light
anaesthesia :
3-5 % in spired air with of
without muscle relaxant.
Deep anaesthesia :
Up to 10 % in inspired air
Preaperation :
• Anaesthetic Ether , I.P.
• Spirit of ether , I.P.

14. # Halothane :
Physical properties :
• Heavy colourless liqud .
• Inflammable, nontoxic fluorinated hydrocarbon .
• Sweet , fruit odor and boil at 500 C .
• It affects most metals including stainless steel , brass and copper
also affect rubber.
Advt :
• Induction is very smooth as it is sweet , fruity odour .
• Recovery is fast , smooth with low incidence of nausea and
vomiting
• Being non-inflammable it does not causes irritation of
respiratory passage.
• It does not produces bronchospasm and laryngospasm , hence
can be used in patient with bronchial asthma .

15. Adverse Effect :
• Mascular relaxation is inadequeate.
• It causes respiratory , cardiovascular depression .
• Shivering during recovery is very common.
• Mental recovery delayed.
• It poor analgesic .
• May increase in chances of hepatic damage.
• It is expensive , need special apparatus for administration
Uses :
Induction and maintainenace of anaesthesia.
Contraindications :
History of unexplained jaundice or pyrexia
following previous exposure to halothane ,
family history of malignant hyperthermia and
porphyria.
Hepatic damage

16. Dosage for induction :
Using calibrated gradually increased gas concentration
2-4 % , for adult and children 1.5 – 2 % in
oxygen or nitrous oxide-oxygen
Maintainance:
For both adult and child 0.5 – 2 %

17. # Chloroform :
Physical Properties :
• It is clear , volatile liquid of boiling point 61º C .
• It is non-explosive liquid which is unstable on
storage .
• It has sweet , appreciable smell.
• It marked in brown coloured bottles to avoid
oxidation by light . It also decomposes in the
presence of flame to form phosgene.

18. Pharmacological action
• Chloroform is highly potent drug which produce all stages of
anaesthesia , without causing hypoxia.
• Just 1 % concentration of chloroform in inspired air is
sufficient for induction of anaesthesia.
• Surgical anaesthesia achieved in 2 to 3 Min.
• Care should be taken to dilute the vapor with pure air to avoid
the possibility of over – dosage .
• First indication of overdose is circulatory collapse.
• Chloroform produce arterial hypotension withoutt much
affecting the heart rate . Hypotension is caused by marked
reduction in cardiac output & may occur cardiac arrest
suddenly administered .
• Chloroform gives cooling sensation on skin i.e. rubifacient .
• Dilute chloroform solution are internally administered as
carminative.

19. Advese Effect :
1. Toxic effect on liver .
2. Repeated doses of chloroform can causes cirrhosis ,
degeneration of heart and kidney.
3. It produces hypotension . Cardiac arrest and arrhythmia.
4. Drug may be produce ventricular fibrillation as well as
respiratory arrest.
5. Drug produce intestinal motility and because of it
chances of paralytic ileus.
Intestinal motility

20. Therapeutic uses :
1. It is powerful anaesthetics agent Because of toxicity
no longer used except in obstetrical anaesthesia .
2. It is counterirritant and rubifacient .
3. It used as carminative stomachic and flavoring agent .
4. Sometimes used as vehicle for excretion of organic
drug.
flavoring agent

21. Gases :
# Nitrous Oxcide :
Physical properties :
• Colourless gas , sweet odour and test , noninflammable , Non –
explosive but strongly support combustion.
• Nitrous oxide is marketed in the liquid form under 50
atmospheric pressure i9n royal blue cylinder.
Advt :
• Produced rapid induction and recovery.
• Good analgesics effect hence can be used in dental practice .
Dis-Advt :
• Pre-anaesthetic medication is required as it is potent anaesthetic.
• Excitement may be violent
• Special apparatus is required.

22. Pharmacological Action :
• Mixture of nitrous oxide gas with
oxygen containing 80 % of it causes
unconsciousness and analgesia
though not full anaesthesia.
• For achieving full surgical
anaesthesia with the gas a higher
concentration ( upto 80 % ) is
necessary which cause anoxia with
cerebral damage , if the inhalation
continues for more medication and
skeletal muscle relaxant .
Anoxia

23. Advese Effect :
• The Produced by nitrous oxide may be violent in certain cases .
• The drug is known to produce hypoxia and cardiac irregularities
during anaesthesia .
• Nitrous oxide is used as supplementary anaesthetics agent .
• Administration of nitrous oxide required administration Of
preanaesthetic medicarion and skeletal muscle relaxants.
Therapeutic uses
• Commonly employed as adjunct to
other anaesthetics agent.
• It is employed for extraction tooth ,
obstetrical analgesia and for certain
painful procedures. extraction tooth

24. Contraindications :
In patient with demonstrable
collection of air in pleural,
Pericardial , Peritoneal space ,
intestinal obstruction , arterial air
embolism , chronic obstructive
airway disease and emphysema.
Dosage :
• Nitrous oxide with 25 to 30 % oxygen.
• For analgesia 50 % nitrous oxide missed
with 50 % oxygen .

25. # Cyclopropane :
Physical Properties:
• Colourless gas with sweet odour and test .
• It is available as liquid under pressure andadninistration in
closed circuit.
• cardiac contractility.
Preparation And Doses :
Cyclopropane I.P. : 30 to 35 % concentration.

26. Therapeutic Effect :
• Potent anesthetic agent.
• Induction is pleasant and quicker.
• Recovery is rapid and smooth .
• Does not irritate respiratory passage .
• Incidence of nausea and vomiting are less.
• It produced adequate muscular relaxation.
• It does not affect B.P. and
Advese Effect
• The sign if anesthesia are not clear .
• Rapid induction may produced laryngospasm ,
breath , holding , tachypnea, coughing .
• It may produced excitement and delirium .
• Stages of anashaesia is not clear ,as induction is very smooth.
• it increase capillary oozing.

27. Mechanism of action of Inhalatory
anaesthetics :
Inhaled anesthetics produce immobility via
actions on the spinal cord . There is consensus that
inhaled anesthetics produce anesthesia by
enhancing inhibitory channels and attenuating
excitatory channels, but whether or not this occurs
through direct binding or membrane alterations is
not known .

28. B) Nonvolatile intravenous anaesthertics
Advt :
• Easy to administer .
• Induction is rapid and smooth .
• Post anaesthetic complication are rare .
• Recovery is very fast .
• Respiratory and myocardial function remains unaffected.
• No irriatation of respiratory passage.
Dis-Advt :
• Usal stages of anaesthesia are not cleare.
• Coughing , apneas is common during induction,
• Muscular relaxation is very poor .
• Ingection around nerve may produces palsy ( paralysis) .
Preaperations :
• Thiopenton sodium  2.5 % solution
• Methohexitone  1 % solution
• Propenamide  4 mg/kg
• Ketamine  1.2 mg/kg
Cerebral palsy

29. # Thiopentone :
Thiopentone sodium is sodium salt of pentobarbitone
which can be uses as anaesthetics agent .
Pharmacological action :
• Nitrous oxide or pethidine together with use of muscle
relaxant .
• The drug may be used in very short operations such as
manipulations or settling of fracture , but this can be
dangerous owing to the possibility of respiratory arrest .
• The drug is commonly administered as an intravenous
injection.2.5 to 5 % solution given by intravenous
Thiopentone is rapidly distributed and act quickly on brain
and effect of an initial dose 25 mg last for about 15 minutes ,
Thus it is ultra short acting .It is poor analgesics

30. Undesirable effects :
It depress respiration and causes coughing , Laryngospasm ,
bronchospasm .
Therapeutic Uses :
It used as intravenously for induction of Anaesthesia and as a basal
anesthetics .
Contraindications :
Inability to maintain air way , hypersensitivity to barbiturates ,
cardiovascular disease , dyspnea , porphyria .

31. PREANAESTHETIC MEDICATION
The pharmacological agent when administerd externally
with an important objectives to make analsthesia mor smooth and
agreeable for the patient , the phenomenon is termed as preanaesthetic
medication.
Aimes and Objectives :
 For sedation – to reduced anxiety
 To obtain an additive and synergestic effect .
 To minimize pre and post operative complication.
 To facilitate smooth and rapid induction.
 To overcome secretary effects of general anaesthetics .
 It Produce synergetic effect or additive effect with anaesthetics
agent, so dose and hence toxicity of anaesthetics agent can be
reduced .

32. No. Type Drug Trade name Dose
1. Opioid Analgesic
(pain killer )
Morphine
Pethidine
-
-
15 mg
15.30 mg
2. Barbiturates Pentobarbitone
Secobarbitone
Nebutal
Lipatone
30 Mg
-
3. Anxiolytic
Tranquilizer :
reduced anxiety
Diazepam valium 5 mg
4. Antihistaminic Promethazine Promawell 25 mg
5. Anticholinergic
agent ( reduce
salivary and
respiratory
secretion )
Atropine or
Hyoscine
Hyosidic
Atrodote
Atrowell
20 mg/ml
IM.IV,SC
1 mg
Some agent ,

33. Basal Anesthetics :
Drug which are produce preliminary and incomplete
anaesthesia induced to prepare a surgical patient for total
anaesthesia with another agent called basal anaesthestics .
E. g.
1. Thiopentone sodium : 2% salt by I.V. After administered
patient become unconscious.
2. Tribromomethanol : It also administered as retention edema
It contain halogen , It has hepatotoxic effect
3. Paraldehyde : It also administered as retention edema.
With tranquilizer and better safety established anaesthetics
they are basal anaesthetics used recent time.