POWDERS

Pharmaceutical powders are solid

dosage forms of medicament in which
one or more drugs are dispensed in
finely divided state with or without
excipients. They are available in
crystalline or amorphous form.
 ADVANTAGES

1. It is used both internally and externally.

2. It is more stable than liquid dosage form.
3. It is convenient for the physician to prescribe a
specific amount of powder.
4. On set of action is faster as compared to tablet,
capsules .because it is easily dissolved in body fluids.
5. Easy to carry
6. Easy to administration to the patient orally by
dissolving in suitable liquids.
 DISADVANTAGE
1. Drugs have bitter taste, nausea and
unpleasant taste cannot be administered in
powder form.
2. Deliquescent and hygroscopic drugs cannot be
dispensed in powder form they are packed in
double wrapping.
3. Drugs which get affected by atmospheric
condition are not suitable for dispense.
4. Quantity less than 100 mg cannot be weighed
conveniently.
GENERAL METHOD OF PREPARATION OF POWDERS
1. During powdering, weighing and mixing there
is a loss of powder which cannot be avoided.
Therefore calculate extra quantity.

2. Dispensing balance are not very sensitive. It is

difficult to weigh the quantity less than 100mg
must be triturated with suitable diluents such
as lactose.
 METHODS OF MIXING OF POWDERS
1.Spatulation

2.Trituration

3.Geometric dilution

4.Sifting & Tumbling

Geometric dilution:
This method is used when potent substance are to be
mixed with a large amount of diluents.
For example: 100 mg potent drug mixed in 900mg of
lactose.
According to geometric dilution-
100mg of potent drug + 100mg of lactose = 200mg
mixture
200mg of potent drug + 200mg of lactose = 400mg
mixture
400mg of potent drug + 400mg of lactose = 800mg
mixture
800mg of potent drug + remaining of lactose=1000 mg
mixture.
Tumbling: In this the powder is mixed in a large
container rotated by an electric motor.
Sifting (Sieveing) :
The powders are mixed by passing through
sifters. This process results in a light fluffy.
It is not suitable for potent drugs.
Tumbling:
It is the process of mixing of powders in a
large container rotated by an electric
motor.
Simple & Compound Powders (Divided
Powders)
i. Simple Powder: They contain only
one ingredient either in crystalline or
amorphous form.
Eg. Asprin 300mg.
ii. Compound Powder: They contain 2
or more ingredients, which are mixed
together and then divided into
individual doses.
Dusting Powder
1- Hygroscopic and Deliquescent Powder
Problem:
Absorption of moisture from air leading to partial
or complete liquefaction.
Solution:
A- Applied in a granular form to decrease the exposed
surface to air.
B- Packed in aluminum foil or in plastic film packets
C- Addition of light magnesium oxide to reduce the
tendency to damp
D- Addition of adsorbent materials such as starch
Examples: - halide salts (ex. Sod. Iodide)
- Certain alkaloids (physostigmine Hcl)
2- Efflorescent powders
Problem:
Crystalline substances which during storage loose
their water of crystallization and change to
powder (to be efflorescent). The liberated water
convert the powder to a paste or to a liquid.
Solution:
Using the anhydrous form, and treating it in a
manner similar to hygroscopic powders
Examples: Alum- atropine sulfate- citric acid-
codeine phosphate
3- Eutectic Mixtures
Problem:
Mixture of substances that liquefy when mixed,
rubbed or triturated together. The melting points
of many eutectic mixtures are below room
temperature.
Solution:
A- using inert adsorbent such as starch, talc,
lactose to prevent dampness of the powder
B- dispensing the components of the eutectic
mixture separately.
Examples:
Menthol- thymol- phenol- salol- camphor
4- Effervescent Powders
Definition: Mixture of organic acid and alkali
effervesces when subjected to water due to
reaction between the acid and the base with
evolution of CO2.
Examples: Citric or tartaric acids with sodium
carbonate or bicarbonate
Uses: The liberated carbon dioxide has the
following advantages:
It masks the bitter and nauseous taste.
It promotes gastric secretions.
It acts as a carminative.
 Pharmaceutical Calculations
•The calculation is an important part of our everyday
life.
•It gives an indication of the size of the quantity.
•The pharmaceutical calculation is to allow the
pharmacist to compound and dispense
pharmaceutical dosage form for their patients
accurately.
•For the safety and care of patients every pharmacist
must be competent in these calculations.
 Systems of weights and measurements

Pharmaceutical Calculation involved in dispensing are divided into

2 systems :
i) Imperial System
ii) Metric System

i) Imperial System:
Is the oldest system of weight and measures.
It involves the measures of weight i.e. mass.
It is further classified as Avoirdupois System and Apothecaries
System.
 a. Avoirdupois system

In this system “pound” (Lb) is the standard unit for weight (mass).
Used to measure weight in day-to-day life.
Used in pharmaceutical measurement of bulk quantity at the time
of buying or selling of pharmaceutical product.
 Eg.
1 lb =l6 (oz) ounce
1 lb = 7000 grains
1 oz. = 7000 /16 grains = 437.5 grains
 b. Apothecaries system

In this system “grain” is the standard unit for weight.

Therefore all the measures of mass (weight) are derived from the
“grain”.
20 grains = 1 Scruple
60 grains = 1 drachm
480 grains = 1 ounce
8 drachms = 1 ounce
16 ounce = 1 pound
7000 grains = 1 pound
* 1 Lb= 453.592 grams= 16 ounce= 7000 grains= 8 drachms
 b. Apothecaries system

Liquid measured in pints (pt) or quart (qt)

Eg .
60 minims (m)= 1 fluiddrachm or fluiddram

1 gallon = 160 fluid ounces.

1/4th of a gallon = 1 quart =40 fl.ounce
1/8th of a gallon = 1 pint =20 fl.ounce
1/160th of a gallon = 1 fl. ounce
1/8th of one fl.ounce = 1 fl. drachm
1/60th of one fl.drachm = 1 minim
1 fluid ounce = 480 minims
1 fluid drachm = 60 minims.
 Abbreviations commonly used in measures of capacity

Latin name Symbol English name Equal to

Minimum M Minim 1 minim

Fluid drachm З fl.drachm 60 minims

Fluid uncial ℥ fl.ounce 480 minims

Octarious O Pint 20 fl.ounces

Congius C Gallon 160 fl. ounces

 METRIC SYSTEM
Metric system is used in the Indian pharmacopeia for the
measurement of weights and capacity. It was implemented in
India from 1st April, 1964 in pharmacy profession. In Metric
system “Kilogram” is the standard unit for measurement of
weight. Therefore all other measures for weight are derived from
kilogram (Kg).
1 Kilogram (Kg) = 1000 grams (g)
1 Hectogram (hg) = 100 grams
1 Decagram (dag) = 10 grams
1 Decigram (dg) =0.1 gram
1 Centigram (cg) = 0.01 gram
1 Milligram (mg) = 0.001 gram
1 Microgram (mcg)= 0.000001 gram
1 gram (g) = 1000 mg
0.1 gram =100 mg
0.01 gram = 10 mg
0.001 gram = 1 mg
 METRIC SYSTEM

Measurement of capacity in Metric system

Measurement of capacity in Metric system

In Metric system, the standard unit for
measure is “ litre ’. Therefore all measures
of capacity are derived from the litre .
Eg .
1 litre (Lt) = 1000 millilitre (ml)
 Inter conversions of Imperial and Metric units

Weight measures 1 grain = 64.8 mg ≡65 mg (for all practical

purposes.)
1 gram = 15.43 gr ≡ 15 gr
1milligram (mg) = 1/65 gr or 1/60 gr
1 kilogram = 2.2 lb (pounds)
 Capacity measures
1 drop = 1minim = 0.06 ml (for all practical
purposes)
1 fl. ounce =29.57ml =30ml
1 millilitre (ml) = 16.23 minims = 15 minims
1 litre = 33.1 fl. ounce
1 fl. drachm = 4 ml
1 fl. ounce =30ml
1 ml = 15 minims
0.06 ml = 1 minim
500ml = 1 pint
l000ml = 1quart
 CALCULATIONS BASED ON DENSITY
Density is defined as the mass of a
substance per unit volume. It has the units
of mass over volume. Specific gravity is
defined as the ratio of the mass of a
substance in air to that of an equal volume
of water. In the metric system both density
and specific gravity are numerically equal.

WEIGHT = VOLUME × DENSITY

1. Calculate the volume of 2kg of glycerin. The density of
glycerin is 1.25g/ml.

2.Calcula the weight of 200 ml of alcohol whose density is 0.816 g/ml.

= 1 57.90ml
 PROOF SPIRIT

The strength of alcohol is calculated in proof

degrees.
The Indian standards of 100% proof spirit is equal
to 57%v/v of ethyl alcohol.
i.e., 100% proof spirit = 57%v/v ethyl alcohol
• If the value is more than 57% then it is said to
be as over proof spirit.
• If the value is less than 57% then it is said to be
as under proof spirit.
 PROOF SPIRIT
In India , the exercise duty is calculated in terms of
rupees per liter of proof alcohol.
So, any percentage volume in volume of alcohol
can be converted into proof strength and vice
versa by using the following method.
i. Multiply the percentage strength of alcohol by
1.753 and deduct 100 from the product.
ii. If the result is positive , it is known as over
proof
iii. If the result is negative , it is known as under
proof.
1.753 is obtained as follows:
57.1 volume of ethyl alcohol = 100 ml of proof spirit.
1 volume of ethyl alcohol = 100 / 57.1
= 1.753 volume of proof spirit
Example problems for Proof Spirit calculations
Calculate the strength of 30 ͦ O.P and 40 ͦU.P
30 ͦ OVER PROOF = 100 + 30 = 130
40 ͦ Under proof = 100 – 40 = 60
 ISOTONIC SOLUTIONS
Isotonic solutions are which have same osmotic
pressure or equal solute concentrations.
0.9% sodium chloride solution is considered to
passes the same osmotic pressure and hence it is
a standard solution which is isotonic with blood
plasma.
Any concentration above this (0.9%) is
considered as hypertonic and below this (0.9%)
is considered as hypotonic.
 ISOTONIC SOLUTIONS
For understanding of the osmolarity and tonicity, erythrocytes are
placed in the solution of various strengths as shown below.

.
 ISOTONIC SOLUTIONS
The methods of calculating isotonicity of are :

1. Freezing point method,

2. Molecular weight methods,
3. Graphical methods,
4. Sodium chloride equivalent method.

 Freezing point method

Freezing point of Blood Plasma & Lachrymal secretions is -0.52 ͦC.
It also holds the same value of 0.9% NaCl Solution.
* All liquids or solutions having freezing point of -0.52 ͦC are
Isotonic to Blood Plasma & Lachrymal secretions.
• Pure water freezes at 0 ͦC.
 Liquid Dosage Form
Liquid dosage form is defined as a drug or
medication suspended or dissolved in liquid
medium which is to be administration orally (by
mouth) or systematically (by parenteral) by
using different techniques, into the skin, muscles,
or veins. Liquid dosage forms are classified as
monophasic and biphasic liquid dosage form. A
monophasic liquid dosage form is one which
contains only one phase where as a biphasic
liquid dosage form contains two phases i.e. solid
in liquid or liquid in liquid.
 Advantages
It is easy to swallow for pediatric and geriatric patients.
Parenterals are suitable for unconscious patients.
The onset of action is faster than tablets and capsules.
Parenterals bypass the first pass metabolism.
The unpleasant taste of the drugs can be masked by
adding sweetening and flavouring agents.
Disadvantages
It is less stability than the solid dosage forms.
It is bulky in nature to difficult carry therefore
transportation cost is high.
The administration of parenteral preparations skilled
person is required whereas for liquid orals accurate dosing
is not possible as the calibrated spoon is required to
measure the dose.
Difficult to formulate poorly soluble drugs in liquid
dosage form.
Hygroscopic drugs absorb moisture and degrade,
therefore can’t be formulated in liquid dosage form.
 Excipients used in liquid dosage forms
CATEGORY ROLE IN FORMULATION EXAMPLES
Solvents Act as dissolving medium Water, alcohol, acetic acid,
(solute) acetone, ethyl acetates, syrups.
Co-solvents Enhance the solubility of solute. Ethanol, Sorbitol, Glycerin,
Propylene glycol.
Buffers Maintain pH of the formulation. Phosphate buffers, Acetate
buffers, Citric Acid, Phosphate
buffers
Antimicrobial/ Prevention of microbial growth Benzyl alcohol, Butyl paraben,
preservatives In the formulation. Phenol, Thiomersal.
Antioxidants Inhibit oxidation Ascorbic acid, Sodium
bisulphate, Thiourea, Butyl
Hydroxy Toluene (BHT),
Tocopherols.
Wetting agents Increase the solubility of drug Sodium Lauryl Sulphate (SLS),
Tween 80, Spans, Lecithins.
Antifoaming agents Decrease the tendency of Simethicone, Organic
foaming phosphates, Alcohols, Paraffin
oils, Sterates and glycols.
 CATEGORY ROLE IN FORMULATION EXAMPLES
Thickening Increase the viscosity of the Methyl cellulose, Hydroxyethyl
medium and prevent sedimentation cellulose,
agents/
Excipients used in liquid dosage forms

Microcrystallince cellulose
Viscosifying agent
Humectants Prevent the evaporation of liquid Propylene glycols, Glycerol,
from the preapration Polyethylene glycol.
Chelating agents It forms complexes with metal ions Disodium EDTA, Dihydroxy ethyl
and prevent drug from the glycine, Citric acid and Tartaric acid.
oxidative reaction
Emulsifying agents Reduce interfacial tension and Sodium Lauryl Sulphate, Cetrimide,
prevent coalescence of the Macrogol esters, Sorbitan esters.
dispersed globules
Flocculating It act by preventing cake formation Starch, Sodium alginate, Carbomer.
in suspension and the sediments
agents
are loosely packed which are easily
redispersed.
Sweetening Impart sweetness and mask the Sucrose, Sorbitol, Saccharin,
bitter taste of the oral liquid Aspartame,
agents
preparations Sucralase.
Colors Impart color to the liquid orals Amaranth, Erythrosin, Eosin,
Tartarazine.
Flavors Impart flavors to the liquid orals Aromatic waters, Syrup.
 Solubility Enhancement Technique
A. Physical modification
1) Eutectic mixture:
When the eutectic mixtue is exposed to water the soluble
carrier dissolves leaving the drug in a microcrystalline state
which solubilize rapidly.
e.g: Mixture of paracetamol and urea.
2. Size Reduction:*
B. Chemical modification
3.Salt formation:
Salts have improved solubility in comparison to the original
drug.
e.g: Alkali metal salts of acidic drugs like penicillin and strong
acid salt of basic drugs like atropin are water soluble than
parent drugs.
Eg. Increase of Diclofenac by making its salt form i.e. Diclofenac Sodium
2. Particle Size Reduction:*
Size reduction increase the surface area of the drug particles
which increase the solubility.
Size reduction can be achieved by
a. Micronization & b. Nanosuspension
a.Micronization :
• The solid drug particles size between 1 to 10 microns by micro-
milling
• Micronization of drugs is done by milling techniques using jet
mill, rotor stator colloid mills etc.
• Micronization is not suitable for drugs having a high dose
number because it does not change the saturation solubility of
the drug .
 2. Particle Size Reduction:*
b. Nanosuspension :
•Nanosuspensions are sub-micron colloidal dispersion of pure
particles of the drug, which are stabilized by surfactants.
• Nanosuspension technology is used for efficient delivery of
hydrophobic drugs .
•The particle size distribution of the solid particles in nano-
suspensions is usually less than one micron with an average
particle size ranging between 200 and 600 nm.
•Advantage : Increased dissolution rate due to larger surface area
exposed.
•Eg., Nanosuspension approach has been employed drugs like
paclitaxel, tarazepide, amphotericin B which are still on research
stage.
4.Change of pH:
This can be achieved in two ways
a) In situ salt formation
b) Addition of buffers to formulation.
e.g: Buffered aspirin tablet.
5. Complexation:
The beta and gamma cyclodextrin having ability
to form molecular inclusion complexes with
hydrophilic drug having poor aqueous solubility.
Cyclodextrin are versatile in having hydrophobic
cavity of suitable enough to accomodate the
lipophilic relatively hydrophilic ---- improved
aqueous solubility
e.g: Barbiturates, Benzodiazepines.
C. Miscellaneous methods
6. Use of surfactant: Surfactant reduced the interfecial tension.
Enhance solubility by promoting wetting and penetration of
dissolution fluid into the solid drug particles.
e.g: Spironolactone(steroids)--- increased solubility by using
surfactant(non ionic polysorbates).
7.Co-solvency : Co-solvents are prepared by mixing miscible or
partially miscible solvents. Weak electrolytes and non-polar
molecules have poor water solubility and it can be improved by
altering polarity of the solvent. The addition of an organic cosolvent
to water can dramatically change the solubility of drugs. Cosolvent
system works by reducing the interfacial tension between the aqueous
solution and hydrophobic solute. Aqueous solvent - Ethanol, sorbitol,
glycerin, propylene glycol. Non aqueous solvent - glycerol dimethyl
ketal, glycerol formal, glycofurol, dimethyl acetamide.
SOME PERANTRALPRODUCT THAT CONTAIN COSOLVENT
1.Diazepam - 10% ethanol + propylene glycol
2.Digoxin - 10% ethanol + propylene glycol