Buffer solutions maintain a fairly constant pH even when small amounts of acid or base are added. There are isotonic, hypotonic, and hypertonic solutions depending on their solute concentration compared to blood or other fluids. Buffer solutions are important for intravenous injections, which should be isotonic with blood plasma. Tonicity can be measured using haemolytic or colligative methods. The colligative method involves measuring properties like freezing point depression, which should be -0.52°C for a solution to be considered isotonic with blood plasma. Calculating tonicity is important for parenteral and ophthalmic preparations.

1. Presented By – Ajay Gautam

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WHAT ARE BUFFER SOLUTION ?????
•A buffer solution is one which maintains
its pH fairly constant even upon the
addition of small amounts of acid or
base.

3. Types of solution…
 ISOTONIC
An isotonic solution is one that has the same osmolarity, or solute
concentration, as another solution. If these two solutions are separated by
a semipermeable membrane, water will flow in equal parts out of
each solution and into the other.
 HYPOTONIC
Having a lower osmotic pressure than a surrounding medium or a fluid
under comparison hypotonic organisms.
 HYPERTONIC
A solution that contains more dissolved particles (such as salt and other
electrolytes).

4. PRACTICALLY SAYING……..
• Illustrated by mixing a small quantity of blood with aqueous sodium
chloride solutions of varying tonicity.
• Isotonic : 0.9 g of NaCl per 100 mL
• Hypotonic : 0.2% NaCl
• Hypertonic : 2.0% NaCl solution

5. GENERAL PRINCIPLES FOR
ADJUSTMENT OF ISOTONICITY
1. Parenteral preparations should be isotonic with blood plasma
(depending on the route of administration).
i. Intravenous injection- isotonicity is always desirable.
ii. Subcutaneous injection- not essential.
iii. Intramuscular- hypertonic.
iv. Intrathecal injection- isotonic
2. Nasal drops- should be isotonic.
3. Ophthalmic preparations- should be isotonic.

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Measurement of Tonicity
The tonicity of solutions may be determined by one of the following
two methods:
• Haemolytic Method
• Colligative Method

7. Haemolytic Method
 The acting principle of this method is the observation of the
effect of various solutions of drugs on the appearance of
RBCs when suspended in those solutions. If, there is no
change in size and shape of RBCs when immersed in test
solution on observing with microscope, then this solution is
isotonic to the blood.

8. COLLIGATIVE METHOD
 It has been determined that solutions having same tonicity
exhibit similar behavior with respect to their colligative
properties such as lowering of vapour pressure,
depression in freezing point, etc. Hence, tonicity of a
solution may be determined by determining its colligative
properties. For making isotonic solutions, the quantities of
substances to be added may be calculated by following
methods:
 Based on molecular concentration
 Based on freezing point data
 Based on sodium chloride equivalent (E) value
 White-Vincent method

9. Colligative Method
Based on freezing point data
In pharmacy, isotonicity calculations are most often performed for
parenteral and ophthalmic solutions which must have a freezing point
depression of 0.52◦C for them to be isotonic with blood plasma and tears.
Therefore a solution is considered to be isotonic if it has a freezing point1
of −0.52◦C.
Amount of adjusting Substance = 0.52 – a/b
0.52 – Constant Value
a – freezing point of 1% solution of un-adjusted solution
b – freezing point of 1% solution of adjusting substance

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APPLICATIONS OF ISOTONICITY
• All the parentals preparations.
• Intravenous solutions , Irrigating solutions , lotions for wounds and
subcutaneous injections.
• Solutions meant for intrathecal injections
• Aqueous solution used for nasal applications
• Opthalmic preparations.

11. FABRIKAM