Class: D. Pharm 1st Year Subject: Pharmaceutical Chemistry - I Topic : Inhalants

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Prepared By
Mr. Subodh V. Kamble
M. Pharm (Pharmaceutical Chemistry)

2. Inhalants
• Inhalants are the drugs or chemicals which in
vapour form are inhaled in the body.
• Some chemicals act as anesthetic in vapour form.
• These are administered by inhalation by a closed
mask method.
• Inhalation of gases causes changes in
physiological functions and brings about
pharmacological actions.
• The pharmacological action & effect is depends
upon the gas, its concentration and condition it is
used.
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3. The passage of air into the lungs to supply the body with oxygen is known
as inhalation, and
The passage of air out of the lungs to expel carbon dioxide is known
as exhalation; this process is collectively called breathing or ventilation.
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4. Role of Oxygen
• Oxygen is important to the living cells. It is
necessary for normal oxidative metabolic
processes in a cell, for the production of energy.
• This energy is used by cells to synthesize
Adenosine Triphosphate (ATP).
• When ATP is hydrolysed, energy is released.
• The enzyme NADH (Nicotinamide adenine
dinucleotide) and FADH (Flavin adenine
dinucleotide) play an important role in the
reaction.
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5. Role of Oxygen
• The transport of oxygen is carried by hemoglobin.
• The concentration of hemoglobin in blood is
important in transport mechanism.
– For men, 13.5 to 17.5 grams per deciliter.
– For women, 12.0 to 15.5 grams per deciliter.
• Oxygen combines with hemoglobin reversibly as :
Hb + O2 HbO2
Where Hb = deoxyhemoglobin
and HbO2 = oxyhemoglobin
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6. Role of Oxygen
• The no. of factors like temp., electrolytes, effect of
carbon dioxide, carbon monoxide, pH etc. affect the
formation and dissociation of oxyhemoglobin.
• Similar to oxygen, carbon dioxide also combines with
hemoglobin and forms carboxyhemoglobin.
• It is a very fast process and reduces the amount of
hemoglobin available to carry oxygen.
• Hemoglobin also has buffering capacity.
– In oxyform it is a strong acid than its reduced (deoxy)
form.
– When H+ ion (from the dissociation of carbonic acid) is
accepted by the reduced hemoglobin, the buffering effect
occurs.
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7. Role of Carbondioxide
• Carbondioxide is readily absorbed and carried
by blood, both in cells and plasma.
• It is produced in the body during metabolic
process.
• Large quantity of carbondioxide produced is
eliminated by lungs in the expired (expelled)
air.
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8. Role of Carbondioxide
• Remaining carbondioxide exists in three forms,
– As a carbonic acid (after combining with water)
– As a carbamino form (after combining with proteins &
hemoglobin)
– As bicarbonates (in combination with other cations)
• The pH of blood is maintained by carbonic acid
formation, and its conversion into bicarbonate
ions.
• The normal carbonic acid to bicarbonate ion ratio
is 1/20.
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9. Role of Carbondioxide
• The change in pH is calculated by
pH = pKa – log [H2CO3]
[HCO3]
• The increase in bicarbonate ions results in
increase in pH of body fluids, while increase in
carbon dioxide as carbonic acid decreases it.
• Both the effects are counterbalanced by
excretion process.
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10. Carbondioxide
CO2 Mol. Wt.: 44.01
• It contains not less than 99% v/v of CO2. For
convenience it is stored in grey coloured
metallic cylinder under compression.
• Preparation:
1) Compounds containing carbon like materials like
coal, coke and oil etc. are burned with an excess
of oxygen.
C + O2 CO2
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11. 2) When carbonate is treated with acid
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12. Carbondioxide
CO2 Mol. Wt.: 44.01
3) Calcium carbonate or sodium bicarbonate when
heated, gives out carbondioxide.
CaCO3 CaO + CO2
NaHCO3 Na2CO3 + H2O + CO2
Carbon dioxide under pressure may dissolve in cold water
and forms carbonic acid and from which carbondioxide is
liberated when pressure is released.
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13. • Properties:
– Carbondioxide is a colourless, odourless gas with
faintly acidic taste.
– It is soluble in water and forms carbonic acid.
H2O + CO2 H2CO3
– Carbondioxide does not support combustion.
(Combustion is a chemical process in which a
substance reacts rapidly with oxygen and gives off
heat).
Carbondioxide
CO2 Mol. Wt.: 44.01
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14. – When a magnesium burns in an atmosphere of
carbondioxide, it gets reduced to carbon and metal
oxide is formed.
2Mg + CO2 2MgO + C
Carbondioxide
CO2 Mol. Wt.: 44.01
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15. • Action and Uses:
– It is used as respiratory stimulant when inhaled.
– It stimulates respiratory and cardiovascular centers.
– The mixture of CO2 with 5% oxygen or up to 10% air is used in
the treatment of carbon monoxide poisoning.
– It is also useful in the treatment of drug addiction.
– It is used to prepare dry ice, which is used in minor surgical
operation for destroying tissues.
– It is widely used in beverage industry for preparation of
concentrated soft drinks.
– It is also used to displace air in some parenteral preparations.
• Assay:
– It is assayed by gasometric type of titration.
Carbondioxide
CO2 Mol. Wt.: 44.01
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16. • Storage and Labeling
– It is stored in metal cylinders.
– The shoulder of cylinder is painted grey and has the name and symbol of
CO2 stenciled on it. 16

17. Nitrous Oxide
N2O Mol. Wt. 44.01
• It contains not less than 95% v/v of N2O.
• The gas is supplied and stored in metal
cylinder.
• It is also called “Laughing Gas” as it produces
an exhilarating (making one feel very happy)
effect when inhaled.
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18. • Preparation:
– It is prepared by thermal decomposition of
ammonium nitrate.
NH4NO3 2H2O + N2O 18

19. Nitrous Oxide
N2O Mol. Wt. 44.01
• Properties:
– It is colourless gas with a slight sweetish odour
and taste.
– It dissolves in water & soluble in alcohol.
– At high temp. (5000 C) it decomposes.
N2O N2 + (O)
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20. Nitrous Oxide
N2O Mol. Wt. 44.01
• Uses:
– It produces anaesthetic effect with analgesia.
– It is used by inhalation for operation of short
duration like dental extraction and abscesses
(collection of pus that has built up within the tissue
of the body).
– It is also effective in calming excited mental
patients.
– It is given by inhalation in 60 – 80 % or with
oxygen 20 – 40 % as required.
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21. Nitrous Oxide
N2O Mol. Wt. 44.01
• Assay:
– It is assayed by gasometric type of titration.
– The apparatus consists of gas burettes connected to
a condenser – manometer.
– Volume of gas in liquid nitrogen is measured.
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22. • Storage and Labeling:
– The gas is stored in metal cylinders under pressure & at a temp. not
exceeding 370 C.
– The cylinder is painted blue.
– The label should state the name of gas & symbol N2O stenciled in paint.22

23. • Oxygen is an important constituent of air and
constitutes about 21% by volume of atmosphere.
• According to I. P. Oxygen contains not less than
99% v/v of O2 with traces of other gases like
argon, nitrogen or hydrogen.
• Preparation:
– By two methods.
1. Fractionation of liquid air
2. Electrolysis of water
Oxygen
O2 Mol. Wt. 32
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24. • The air is purified by removing moisture, cabondioxide,
dust etc. and then compressed to get liquid air.
• The liquid air is fractionated by distillation, to get oxygen
which is then filled under pressure in metallic cylinders.24

25. • A direct current is passed through a cell between the iron or steel
electrodes immersed in about 10% aq. Solutions of sod. or pot.
Hydroxide.
• Oxygen is liberated at anode and the hydrogen at cathode.
• The liberated oxygen is then filled under pressure in metallic
cylinders. 25

26. • Properties:
– Oxygen is a colourless, tasteless gas and has a density
of 1.105 g/L.
– It dissolve in about 32 volumes of water, 36 volumes
of alcohol at 1 atmospheric pressure.
– Oxygen is reactive chemically and functions as
oxidizing agent.
– Oxygen gas for medicinal use should not contain
impurity of carbon dioxide (not more than 5 ppm),
carbon monoxide (not more than 30 ppm) and
halogens.
Oxygen
O2 Mol. Wt. 32
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27. • Chemical Properties:
– Non metals like sulphur, carbon and phosphorus
combine with oxygen when heated to form oxides.
S + O2 SO2
C + O2 CO2
4P + 5O2 2P2O5
Oxygen
O2 Mol. Wt. 32
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28. • Chemical Properties:
– Most metals when heated, combine with oxygen
and forms oxides.
4Fe + 3O2 2FeO3
2Mg + O2 2MgO
Oxygen
O2 Mol. Wt. 32
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29. • Action and Uses:
– It is required by living cells. In blood it combines with
haemoglobin and carried to the cells.
– It is widely used in the treatment of hypoxia (Oxygen
deficiency).
– It is administered by mask in a conc. Ranging from 40 – 100%
of oxygen.
– It is used in treatment of anoxia (an absence of oxygen / severe
hypoxia) which results due to inadequate oxygenation of blood.
– It is useful in carbon monoxide poisoning.
– In industry it is used for welding and cutting metals.
– Liquid oxygen is used as fuel in rocket.
• Assay:
– It is assayed by gasometric method.
Oxygen
O2 Mol. Wt. 32
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30. • Storage and labeling:
– It is stored in metal cylinders under pressure.
– The shoulder of cylinder is painted white and remained part is painted
black.
– The name and symbol of Oxygen (O2) is stenciled on the shoulder of the
cylinder. 30

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