powders Flashcards
Pharmaceutical material
medicinal substances, pharmaceutical excipients
premixes
animal food
advantages of powders
larger surface area, alt way of dose administration, flexible, good chemical stability, easier for pt to take
larger surface area of powders
compared to tables and/or capsules
An alternative method of administering the dose
patient cannot swallow a capsule or a tablet (e.g., via a nasogastric tube)
small children (the drug may be administered with apple sauce
can u give larger doses w powders
YES
Good chemical stability of powders
chemical degradation of most drugs is due to hydrolysis - powder dosage forms are essentially devoid of moisture
- chemical degradation of a drug is minimized in a powder dosage form
disadvantages of powders
not a good dosage form, not accurate, time consuming
why are powders not a good dosage form
for hygroscopic, deliquescent, and efflorescent drugs » for unpleasant taste and/or odor drugs
why are doses not an accurate dosage form
» bulk powders do not provide accurate doses because the dose is measured using a house- hold teaspoon
» the accuracy of dose in bulk powders is even less than the accuracy of dose in divided powders
medicinal substances of powders
crystalline and powdered forms
subdivision of particles
– Manufacturing process
– Therapeutic effects
– Powder fineness (particles size)
Particle size according to
fineness of powders
chemicals and natural drugs
d50 sieve opening method
natural drug power and sieve opening for very coarse
8, 2360
natural drug power and sieve opening for coarse
20, 850
natural drug power and sieve opening for moderately coarse
40, 425
natural drug power and sieve opening for fine
60, 250
natural drug power and sieve opening for very fine
80, 180
chemical power and sieve opening for coarse
20 and 850
chemical power and sieve opening for moderately coarse
40 and 425
chemical power and sieve opening for fine
80, 180
chemical power and sieve opening for very fine
120, 125
very coarse sieve opening
> 1000
coarse sieve opening
335-1000
moderately fine sieve opening
180-355
fine sieve opening
125-180
very fine sieve opening
90-125
Sieving method
50-3360μm
Microscopic method
0.2-100μm
Sedimentation rate
0.8-300μm
– Stokes’ low
Light energy diffraction
0.5-500 microm
laser holograph
1.4-100 micro meters
Physico-Chemical Properties of Powders
A function of particle size and surface area
Surface area formula
(pi)(diameter)^2
Physical characteristics
Ease of mixing
– Dispersibility
» suspension and ointment
» Stoke’s law
– Pharmaceutical elegance
Spatulation
- Soft agglomerates
– Hard-rubber spatulas versus steal spatulas
Trituration
Grinding a drug with a pestle in a mortar to reduce its particle size
levigation
levigating agent
Pulverization by intervention
Hard crystalline substances
– Gummy type substance
Wedgwood
Highly durable and porous
– Hard crystalline solids
– Not for drugs that stain, very small quantity, and very potent
– Re-roughen
Glass
Smooth, non-porous interior surface
– Solutions and suspensions
Porcelain
Similar to Wedgwood mortar
– Glazed and less porous than
Wedgwood mortar
what makes a good powder?
finest state of subdivision, allows for creation of a homogeneous powder (uniform distribution), fast dissolution, and better bioavailability etc
good powders give insoluble powders ____
absorptive capacity (large surface area) for topical application
good powders are ____ than those containing coarse particles (fine particles at 50-100 microm)
LESS
good powders provide _______ for inhaled powders for deposition deep in the respiratory tract (fine particles at 1-5microm)
better penetrability
good powders settle slowly or quickly
SLOWLY (small particles at 0.5-10 microm)
Blending of Powders methods
- Spatulation
– Tumbling
» hazardous or cytotoxic substances
» light-weight powders - trituration
Rule of mixing
The smallest quantity in the formulation (except colorant and flavoring agent) goes into the mortar first
– This is followed by the next larger quantity. Geometric dilution should be used wherever necessary
– The mixture should be triturated to assure complete mixing after each addition of the powder
– Always add powder with higher density to powder with the lower density because lighter powder tends to “dust out” of the mortar
Geometric dilution
Used when blending two or more powder ingredients of unequal quantities
– It is a method designed to help ensure that small quantities of ingredients, usually potent drugs, are uniformly distributed throughout the powder mixture
Trituration usually is the blending method of choice because
gives more intimate mixing than other methods
Special Problems
Hygroscopic and deliquescent substances
Efflorescent powders
Eutectic mixtures
Explosive mixtures
chemical incompatibilities
incorporation of small amounts of liquids
explosive mixtures
React violently when mixed together
» oxidizing agents and reducing agents
– Examples
» iodine,nitrates,etc
chemical incompatibilities
Visually evident and physicochemical phenomena
– Examples
»concentration dependent precipitation
» acid-bas ereaction
» discoloration
» chemical deterioration
» loss of potency
Hygroscopic and Deliquescent Substances
solids that absorb moisture from the air (partially or wholly dissolves in moisture once enough is absorbed)
what dosage form do you prefer Hygroscopic and Deliquescent Substances in
LIQUID (solution or suspension)
- Check with the prescriber if a liquid dosage form would be acceptable
– If not, the powder must be dispensed in a form that is usable and acceptable to the patient
what do you add to Hygroscopic and Deliquescent Substances
water insoluble powdered ingredient (To prevent or minimize water-absorption)
light magnesium oxide
the quantity used is not sufficient to impart the laxative effect
» light magnesium oxide is preferred over heavy magnesium oxide
how should Hygroscopic and Deliquescent Substances be dispensed
in a tight container (Should be double-wrapped in wax-paper or sealed in plastic or foil and the packets put in
tight containers)
hygroscopic substances examples
ammonium iodide, ephedrine sulfate, phenobarbital sodium, potassium phosphate (dibasic), sodium phosphate (dibasic)
deliquescent substances examples
lithium bromide, potassium acetate, sodium iodide, zinc chloride
efflorescent powders
crystalline substances that contain water of hydration or crystallization
– This water can be released when the substance is manipulated or triturated
liberation of water of efflorescent powders causes
powdered substance to become damp or take the appearance of a paste (A given weight of the prepared powder no longer contains the same amount of drug due to the loss of water)
how should efflorescent powders be stored
tight containers
efflorescent powders- Substitute the anhydrous form of the drug for ________
the form that contains water of hydration
examples of efflorescent powders
citric acid, magnesium sulfate heptahydrate, quinine hydrochloride dihydrate, sodium carbonate decahydrate, strychnine sulfate pentahydrate
euctectic mixtures
liquefy when they come into contact with each other
presence of one solid in euctectic mixtures
acts as an impurity for the other substance (mp of each solid lowered)
The resultant melting point of the solids in euctetic mixtures
greater than room temp (powder mixture poses as no issue)
The resultant melting point of either solid ingredient (euctectic mixtures)
near or below room temp
The solids may become damp, pasty, or liquid, depending upon the melting point lowering
The eutectic mixture results in a liquid much faster when the low melting point components are combined
Methods to handle eutectic mixtures
Allow the liquid eutectic to form and absorb the liquid onto an inert, high-melting, finely divided solid
» use a low-density absorbing solid (e.g., light magnesium oxide or kaolin) in order to use a minimum weight of the absorbing solid
– Triturate the potential eutectic formers separately with an inert ingredient, then mix the protected powders together by gentle spatulation or by tumbling(use a low-density inert ingredient so as to use the minimum weight of the inert ingredient)
Incorporation of Relatively Small Proportion of Liquids method
Absorb the liquid into the powder (triturate liquid w an equal amount of powder)
The remainder of the powder is then incorporated by _______ (euctectic mixture)
adding it in several portions (with trituration) until the entire quantity of the powder has been added
An absorbent inert powder, if needed, may be incorporated (when adding in small amounts of liquids)
To produce the final mixture as a dry powder
– Light or heavy magnesium oxide, or kaolin
Powders for internal use
Not to use an excessive quantity of the absorbent powder which tends to exhibit some pharmacological effects at high doses
kaolin
used in the treatment of diarrhea, but only if the diarrhea- causing agent can be adsorbed by kaolin
magnesium oxide
effective, fairly long-acting, non-systemic antacid, but is also used as a cathartic
Bulk powders
Powders for topical application
– Powders for internal use
– Example
» CBZ Dusting Powder
Divided powders
– Powder papers
vegetable parchment, white bond, waxed, glassine
vegetable parchment paper
thin semiopaque moisture-resistant paper
white bond paper
opaque paper with no moisture- resistant properties
waxed paper
transparent waterproof paper
glassine paper
glazed, transparent moisture-resistant paper
divided powder example
Aspirin Phenacetin Caffeine Powder
effervescent granules:
Carbonation can mask the bitter or unpleasant taste of drug
effervescing agent: citric acid reacts with sodium bicarbonate
210 g vs 254 g
tartaric acid reacts with sodium bicarbonate
150g vs 168g
Problems using citric acid and tartaric acid
- Citric acid: difficult to granulate
– Tartaric acid: chalky, friable and not firm granules
Component of formulation
- Citric acid: 1 part
– Tartaric acid: 2 parts
– Sodium bicarbonate: 3.4 parts
