Rheology is important for pharmacists in understanding the flow properties of emulsions, suspensions, and other dosage forms. It also affects the selection of processing equipment and containers. For suspensions and emulsions, rheology determines properties like sedimentation, redispersibility, and flow characteristics. The viscosity and rheological class (e.g. Newtonian, pseudoplastic) of a dosage form depends on factors like particle size, concentration, and choice of suspending agent. Container materials must be compatible with the dosage form and maintain seal integrity over time. Rheology is a key consideration in designing stable, easily administered pharmaceutical preparations.
Rheology is the science that study flow of fluids. Viscosity is the main parameter of flow. Newtonian & non newtonian are the two types of flow behavior according to newtons law of flow. non-newtonian flow can be plastic, pseudoplastic, dilatant, thixotropic, antithixotropic or rheopexy. viscosity can be determined by using various viscometers such as capillary viscometer, cup & bob viscometer, cone & plate viscometer, falling sphere viscometer, brookfield viscometer, etc. factors affeting viscosity are intrinsic, extrinsic or temperature dependence.
Rheology is the science that study flow of fluids. Viscosity is the main parameter of flow. Newtonian & non newtonian are the two types of flow behavior according to newtons law of flow. non-newtonian flow can be plastic, pseudoplastic, dilatant, thixotropic, antithixotropic or rheopexy. viscosity can be determined by using various viscometers such as capillary viscometer, cup & bob viscometer, cone & plate viscometer, falling sphere viscometer, brookfield viscometer, etc. factors affeting viscosity are intrinsic, extrinsic or temperature dependence.
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
Presentation include chapter solubility of drugs from second yr B-Pharm
Solubility, solubility expression, solute solvent interactions, solubility parameters, solvation and dissolution, factors affecting solubility, solubility of gases in liquids, liquids in liquids, fractional distillation, azeotropes, dissolution and drug release and diffusion.
Settling in Suspensions, Formulation of Flocculated and Defloculated Suspens...Suyash Jain
Suspension
Settling in Suspensions,
Stroks law
Theory Of Sedimentation
Formulation of suspensions
Precipitation method:
Dispersion method
Comparision of partical setteling in Defloculated Suspension and Floculated Suspension
Characteristics of an Ideal Suspensions
Formulation of Flocculated and Defloculated Suspensions
Solubility of drugs: Solubility expressions, mechanisms of solute solvent interactions, ideal solubility parameters, solvation & association, quantitative approach to the factors
influencing solubility of drugs, diffusion principles in biological systems. Solubility
of gas in liquids, solubility of liquids in liquids, (Binary solutions, ideal solutions)
Raoult’s law, real solutions. Partially miscible liquids, Critical solution temperature . Distribution law, its limitations and applications
State of matter and properties of matter (Part-2) (Latent Heat, Vapour pressu...Ms. Pooja Bhandare
Latent Heat, Vapour pressure, Factor affecting vapour pressure, Surface area, Types of molecule, Temperature and Intermolecular forces, Sublimation Critical point
Surface Tension is defined as the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
It is due to the phenomena of surface tension that the drops of water tend to assume a spherical shape to attain minimum surface area. the presentation gives a brief description of the methods to measue this important property of the interface of two fluid.
Presentation include chapter solubility of drugs from second yr B-Pharm
Solubility, solubility expression, solute solvent interactions, solubility parameters, solvation and dissolution, factors affecting solubility, solubility of gases in liquids, liquids in liquids, fractional distillation, azeotropes, dissolution and drug release and diffusion.
Settling in Suspensions, Formulation of Flocculated and Defloculated Suspens...Suyash Jain
Suspension
Settling in Suspensions,
Stroks law
Theory Of Sedimentation
Formulation of suspensions
Precipitation method:
Dispersion method
Comparision of partical setteling in Defloculated Suspension and Floculated Suspension
Characteristics of an Ideal Suspensions
Formulation of Flocculated and Defloculated Suspensions
Solubility of drugs: Solubility expressions, mechanisms of solute solvent interactions, ideal solubility parameters, solvation & association, quantitative approach to the factors
influencing solubility of drugs, diffusion principles in biological systems. Solubility
of gas in liquids, solubility of liquids in liquids, (Binary solutions, ideal solutions)
Raoult’s law, real solutions. Partially miscible liquids, Critical solution temperature . Distribution law, its limitations and applications
Hydropericardium-Hepatitis Syndrome, Angara Disease in broiler chickenDr.Kedar Karki
This condition was first identified in broilers in Pakistan in 1987. It spread rapidly in broiler producing areas in that country and the same or a very similar condition has been seen in North and South America. It affects mainly broilers and broiler parents in rear and has also been seen in pigeons.
An overview of Inclusion body hepatitis-hydropericardium syndrome (IBH-HPS) a...Dr.Kedar Karki
IBH/HPS is an acute infectious disease characterized by typical hydropericardium, severe anaemia, necrotic hepatitis and high mortality. In natural outbreaks, the affected birds may not exhibit any clinical signs (Jaffery, 1988) except sudden heavy mortality (Ravikumar et al., 1997). Mortality rates in various outbreaks range from 15- 60% (Asrani et al., 1997).
What’s a suspension ?
Suspension Requirements?
Why a suspension?
Stability;
HOW TO MAKE A FINE POWDER? (10-50 MICRON)
Fluid Energy
Preparing Flocculated suspensions
Formulation considerations for orally administered suspension:
Rheology
Rheology for Pharmacists
Excipients used in the formulation of suspensions for oral administration:
Excipients used in the formulation of suspensions for oral administration:
Some subdosage forms of suspensions
Extemporaneous Prepration:
This ppt was made by my friend Svenia & I. It is a summary of the journal on 'Influence of mineral and vitamin supplements on pregnancy outcome'.
Hope it helps.
This is a summary of the journal : 'Is there more to learn about functional vitamin D metabolism?' presented by my friend Svenia and me. Hope it helps.
This presentation is on ocean acidification, it covers
(1) a background on ocean acidification,
(2) the chemistry between carbon dioxide & the ocean
(3) Impact of Ocean acidification on biological processes and the ecosystems.
(4) and finally some mitigation measures
I hope this ppt be useful & helpful to people working on this topic :)
Enjoy
This is a portfolio on 5 different plants with pharmacological properties prepared by my colleague Svenia and Myself. It covers some important aspects such as background, uses and preparations etc. Hope it helps.
Gap junctional intercellular communication in cancer chemopreventionNabiilah Naraino Majie
This powerpoint presentation gives an overview of how gap junctions are involved in cancer. And how it can be upregulated by the action of phytochemicals in the process of cancer chemoprevention. I have used a scientific journal to eleborate on the mechanism. I hope it helps.
This ppt explains the basics of mass spectrometry and in application in pharmacognosy. Hope this helps you guys. Like, comment and save. If you hav problem downloading, send your email address; i'll post it for you by mail :)
Enjoy the presentation.
This presentation is on the bioassay of heparin which helps to know the potency of new heparin drug or heparin conc in individual suffering from heparin resistance diseases.
This was made by my friend Naailah and me. Hope it helps.
This prsentation explains the use of biomarker with reference to an article: Accelerating Drug Develeopment using Biomarkers-Sitagliptin.
It was presented my my 2 friends and me. Hope it helps you guys.
A presentation on Paul Ehrlich developed modern chemotherapy. This was my ppt for the module pharmaceutics 6. It i based on Anti microbial chemo; hope it help others doing relating things.
This was my pharmaceutics presentation for mixing. Provides definitions, mechanism, types of mixers etc.
P.S: I am not the sole presenter. Ideas are from my two other colleagues as well.
Adv. biopharm. APPLICATION OF PHARMACOKINETICS : TARGETED DRUG DELIVERY SYSTEMSAkankshaAshtankar
MIP 201T & MPH 202T
ADVANCED BIOPHARMACEUTICS & PHARMACOKINETICS : UNIT 5
APPLICATION OF PHARMACOKINETICS : TARGETED DRUG DELIVERY SYSTEMS By - AKANKSHA ASHTANKAR
ABDOMINAL TRAUMA in pediatrics part one.drhasanrajab
Abdominal trauma in pediatrics refers to injuries or damage to the abdominal organs in children. It can occur due to various causes such as falls, motor vehicle accidents, sports-related injuries, and physical abuse. Children are more vulnerable to abdominal trauma due to their unique anatomical and physiological characteristics. Signs and symptoms include abdominal pain, tenderness, distension, vomiting, and signs of shock. Diagnosis involves physical examination, imaging studies, and laboratory tests. Management depends on the severity and may involve conservative treatment or surgical intervention. Prevention is crucial in reducing the incidence of abdominal trauma in children.
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachAyurveda ForAll
Explore the benefits of combining Ayurveda with conventional Parkinson's treatments. Learn how a holistic approach can manage symptoms, enhance well-being, and balance body energies. Discover the steps to safely integrate Ayurvedic practices into your Parkinson’s care plan, including expert guidance on diet, herbal remedies, and lifestyle modifications.
Here is the updated list of Top Best Ayurvedic medicine for Gas and Indigestion and those are Gas-O-Go Syp for Dyspepsia | Lavizyme Syrup for Acidity | Yumzyme Hepatoprotective Capsules etc
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
Basavarajeeyam is a Sreshta Sangraha grantha (Compiled book ), written by Neelkanta kotturu Basavaraja Virachita. It contains 25 Prakaranas, First 24 Chapters related to Rogas& 25th to Rasadravyas.
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SURGICAL ANATOMY OF THE RETROPERITONEUM, ADRENALS, KIDNEYS AND URETERS.pptx
Assignment on rheology
1. UNIVERSITY OF MAURITIUS
Bachelor of Pharmacy – Year 2
PHARMACEUTICS III
TITLE:
‘To the pharmacist, rheology is important in
the flow of emulsions, through colloid mills,
triturating suspensions in mortar and pestle
and mechanical properties of glass or plastic
containers and of rubber closures’. Discuss.
Presented by:
NARAINO MAJIE Nabiilah - 1216824
Date of Submission: 29th April 2014
2. INTRODUCTION
Rheology is the science concerned with the deformation of matter under the influence of
stresses, which may be applied perpendicularly to the surface of a body (a tensile stress),
tangentially to the surface (a shearing stress), or at any other angle to the surface. The
deformations that result from the application of stress may be divided into two types:
1. Spontaneously reversible deformations or elastic deformations, and
2. Permanent or irreversible deformations that are referred to as flow and are exhibited by
viscous bodies.
The work used in producing an elastic deformation is recoverable when the body returns to
its original shape after removal of the applied stress. However, in irreversible deformations
the work used in maintaining deformation is dissipated as heat and is not recoverable
mechanically when the stress is removed.
From the rheological viewpoint systems are:
Solid if they preserve shape & volume.
Liquid if they preserve their volume.
Gaseous if neither the shape nor volume remains constant when forces are applied to
them
The shear stress that causes a particular rate of shear is obtained by dividing the shearing
force by the area of the surface of the surface to which the shearing force is tangentially
applied. The ratio of the applied shear stress to the rate of shear is known as the coefficient of
viscosity. The simplest definition of viscosity is resistance to flow. Sir Isaac Newton defined it as
“the resistance that arises from lack of slipperiness in a fluid.” The effect of rate of shear on this ratio
varies for different systems which have led to these systems to be classified into the following
types:
1. Newtonian
Fluids which obey the Newton's law of viscosity are called as Newtonian fluids. Newton's
law of viscosity is given by
τ = μdv/dy ;
where τ = shear stress
μ = viscosity of fluid
dv/dy = shear rate, rate of strain or
velocity gradient
3. All gases and most liquids which have simpler molecular formula and low molecular weight
such as water, benzene, ethyl alcohol, CCl4, hexane and most solutions of simple molecules
are Newtonian fluids.
2. Non-Newtonian
Fluids which do not obey the Newton's law of viscosity are called as non-Newtonian fluids.
Generally non-Newtonian fluids are complex mixtures: slurries, pastes, gels, polymer
solutions etc.
Various non-Newtonian Behaviours:
Time-Independent behaviours:
These are properties are independent of time under shear.
Bingham-plastic: Resist a small shear stress but flow easily under larger shear stresses.
e.g. tooth-paste, jellies, and some slurries.
Pseudo-plastic: Most non-Newtonian fluids fall into this group. Viscosity decreases with
increasing velocity gradient. e.g. polymer solutions, blood. Pseudoplastic fluids are also
called as Shear thinning fluids. At low shear rates (du/dy) the shear thinning fluid is more
viscous than the Newtonian fluid, and at high shear rates it is less viscous.
Dilatant fluids: Viscosity increases with increasing velocity gradient. They are
uncommon, but suspensions of starch and sand behave in this way. Dilatant fluids are also
called as shear thickening fluids.
4. Time dependent behaviours:
These are properties which are dependent upon duration of shear.
Thixotropic fluids: for which the dynamic viscosity decreases with the time for which
shearing forces are applied. e.g. thixotropic jelly paints.
Rheopectic fluids: Dynamic viscosity increases with the time for which shearing forces
are applied. e.g. gypsum suspension in water.
Visco-elastic fluids: Some fluids have elastic properties, which allow them to spring back
when a shear force is released. e.g. egg white.
In manufacturing, having a complete rheological understanding of the material being
processed is important to verify the equipment can effortlessly handle the job and perform it
in an accurate and reproducible manner.
In pharmaceutical industries, rheology is involved in the study of viscosity is of true liquids,
solutions, dilute and concentrated colloidal systems. It is also involved in the mixing and flow
of materials, their packaging into containers, and the pouring from the bottle, extrusion from
a tube or a passage of the liquid to a syringe needle. It can affect the patient’s acceptability of
the product, physical stability, biologic availability, absorption rate of drugs in the
gastrointestinal tract and influence the choice of processing equipments in the pharmaceutical
system.
5. IMPORTANCE OF RHEOLOGY IN SUSPENSIONS
The rheological properties of suspensions are markedly affected by the degree of
flocculation. The reason for this is that the amount of free continuous phase is reduced, as it
becomes entrapped in the diffuse floccules. Consequently, the apparent viscosity of a
flocculated suspension is normally higher than that of a suspension which is in all ways
similar, with the exception that it is deflocculated.
In addition, when a disperse system is highly flocculated then the possibility of interaction
between floccules occurs and structured systems result. If the forces bonding floccules
together are capable of withstanding weak stresses then a yield value will result, and below
this value the suspension will behave like a solid. Once the yield value has been exceeded the
amount of structural breakdown increases with increased shear stress. Therefore, flocculated
suspensions will exhibit plastic or, more usually, pseudoplastic behaviour. Obviously, if the
breakdown and reformation of the bonds between floccules is time dependent then
thixotropic behaviour will also be observed.
The formation of structures does not occur in deflocculated suspensions and so their
rheological behaviour is determined by that of the continuous phase together with the effect
of distortion of the flow lines around the particles; in this situation the
Einstein equation may apply. The equation is as follow:
r
+2.5
As the suspension becomes more concentrated and the particles come into contact, then
dilatancy will occur.
Many pharmaceutical products, particularly those for children, are presented as suspensions
and their rheological properties are important. In general these properties must be adjusted so
that:
1. The product is easily administered (e.g. easily poured from a bottle or forced through a
syringe needle);
2. Sedimentation is either prevented or retarded; if it does occur, redispersion is easy;
3. The product has an elegant appearance.
Deflocculated particles in Newtonian vehicles
When such systems sediment, a compact sediment or cake is produced which is difficult to
redisperse. The rate of sedimentation can be reduced by increasing the viscosity of the
continuous medium, which will remain Newtonian. However, there is a limit to which this
viscosity can be increased because difficulty will be experienced, for example, in pouring the
6. suspension from a bottle. Furthermore, if sedimentation does occur, then subsequent
redispersion may be even more difficult.
Deflocculated particles in non-Newtonian vehicles
Only pseudoplastic or plastic dispersion media can be used in the formulation of suspensions
and both will retard the sedimentation of small particles, as their apparent viscosities will be
high under the small stresses associated with sedimentation. Also, as the medium will
undergo structural breakdown under the higher stresses involved in shaking and pouring, both
these processes are facilitated.
The hydrocolloids used as suspending agents, such as acacia, tragacanth, methylcellulose,
gelatine and sodium carboxymethylcellulose, all impart non- Newtonian properties -
normally pseudoplasticity -to the suspensions. Thixotropy can occur and this is particularly
the case with the mineral clays, such as bentonite (which must only be used in suspensions
for external use). The three-dimensional gel network traps the deflocculated particles at rest
and their sedimentations retarded and may be completely prevented. The gel network is
destroyed during shaking so that administration is facilitated. It is desirable that the gel
network is reformed quickly so that dispersion of the particles is maintained.
Flocculated particles in Newtonian vehicles
Such particles will still sediment, but because the aggregates are diffuse a large volume
sediment is produced and, as such, is easier to disperse. These systems are seldom improved
by an increase in the viscosity of the continuous phase as this will only influence the rate of
sedimentation. The major problem is one of pharmaceutical inelegance, in that the sediment
does not fill the whole of the fluid volume.
Flocculated particles in non-Newtonian vehicles
These systems combine the advantages of both methods. Furthermore, variations in the
properties of the raw materials to be suspended are unlikely to influence the performance of a
product made on production scale. Consequently, less difference will be observed between
batches made by the same method and plant.
7. IMPORTANCE OF RHEOLOGY IN EMULSIONS
Emulsions consist of droplets of one liquid dispersed in another immiscible liquid. The
rheology of emulsions has many similar features to that of suspensions. However, they differ
in three main aspects:
(i) The mobile liquid/liquid interface that contains surfactant or polymer layers introduces a
response to deformation and one has to consider the interfacial rheology,
(ii) The dispersed-phase viscosity relative to that of the medium has an effect on the rheology
of the emulsion,
(iii) The deformable nature of the dispersed-phase droplets, particularly for large droplets, has
an effect on the emulsion rheology at high phase volume fraction, φ.
Because nearly all but the most dilute of medicinal emulsions exhibit non-Newtonian
behaviour, their rheological characteristics have a marked effect on their usefulness. The fluid
emulsions are usually pseudoplastic, and those approaching a semisolid nature behave
plastically and exhibit marked yield values. The semisolid creams are usually viscoelastic.
A considerable variety of pharmaceutical products can be formulated by altering the
concentration of the disperse phase and the nature and concentration of the emulsifying agent.
The latter can be used to confer viscoelastic properties on a topical cream merely by varying
the ratio of surface-active agent to long-chain alcohol.
Factors that affect rheology of emulsions
These factors are:
The volume fraction of the disperse phase,
The viscosity of the disperse droplets,
The droplet size distribution,
The viscosity and chemical composition (ph, electrolyte concentration, etc.) Of the
medium,
The interfacial rheology of the emulsifier film and
The concentration and nature of the emulsifier.
Viscosity of the continuous phase
It has been well documented that a direct relationship exists between the viscosity of an
emulsion and the viscosity of its continuous phase. Syrup and glycerol, which are used in oral
emulsions as sweetening agents, will increase the viscosity of the continuous phase. Their
main disadvantage is in increasing the density difference between the two phases, and thus
possibly accelerating creaming. Hydrocolloids, when used as emulsifying agents in o/w
8. emulsions, will stabilize them not only by the formation of multimolecular layers around the
dispersed globules, but also by increasing the continuous phase viscosity. They do not have
the disadvantage of altering the density of this phase. If oil is the continuous phase, then the
inclusion of soft or hard paraffin or certain waxes will increase its viscosity.
Viscosity of the dispersed phase
For most practical applications it is doubtful whether this factor would have any significant
effect on total emulsion viscosity. It is possible, however, that a less viscous dispersed phase
would, during shear, be deformed to a greater extent than a more viscous phase, and thus the
total interfacial area would increase slightly. This may affect double-layer interactions and
hence the viscosity of the emulsion.
Nature and concentration of the emulsifying system
It has already been shown that hydrophilic colloids, as well as forming multimolecular films
at the oil/water interface, will also increase the viscosity of the continuous phase of an o/w
emulsion. Obviously, as the concentration of this type of emulgent increases so will the
viscosity of the product. Surface-active agents forming condensed monomolecular films will,
by the nature of their chemical structure, influence the degree of flocculation in a similar
way, by forming linkages between adjacent globules and creating a gel-like structure. A
flocculated system will exhibit a greater apparent viscosity than its deflocculated counterpart
and will depend on surfactant concentration.
RHEOLOGICAL SIGNIFICANCE ON PROPERTIES OF CONTAINERS OF
SUSPENSIONS AND EMULSIONS
Typical liquid-based oral dosage forms are elixirs, emulsions, extracts, fluidextracts,
solutions, gels, syrups, spirits, tinctures, aromatic waters, and suspensions. These products are
usually non sterile but may be monitored for changes in bio burden or for the presence of
specific microbes. These dosage forms are generally marketed in multiple-unit bottles or in
unit-dose or single-use pouches or cups. The dosage form may be used as is or admixed first
with a compatible diluent or dispersant. A bottle is usually glass or plastic, often with a screw
cap with a liner, and possibly with a tamper-resistant seal or an overcap that is welded to the
bottle. The same cap liners and inner seals are sometimes used with solid oral dosage forms.
A pouch may be a single-layer plastic or a laminated material. Both bottles and pouches may
use an overwrap, which is usually a laminated material. A single-dose cup may be metal or
plastic with a heat-sealed lid made of a laminated material. A liquid-based oral drug product
9. typically needs to be protected from solvent loss, microbial contamination, and sometimes
from exposure to light or reactive gases (e.g., oxygen).
Container-closures (or 'stoppers' or 'bungs') are an important part of the final packaging for
pharmaceutical preparations, particularly those which are intended to be sterile. The most
commonly used type of stopper is an 'elastomeric' container-closure. An elastomer is any
material that is able to resume its original shape when a deforming force is removed (this is
known as viscoelasticity).
Before using a container-closure in a vial or bottle with a drug product, the container-closure
must be assessed to determine if it is suitable for use with the product that will be filled into
the glass container. The user should consider the following questions relating to product
compatibility, in conjunction with the manufacturer of the container-closure:
Is the product absorbed by the rubber?
Does the rubber react with the product and leach out impurities?
At which temperature range are the closure and product stable?
How effective is the seal integrity?
What happens when the product and stopper are stored together over time (a stability
trial)?
Once these questions have been satisfactorily answered, the user can work with the
manufacturer to design the optimal container-closure for the vial design and product.
REFERENCES
1. David J Mastropietro, Rashel Nimroozi and Hossein Omidian, 2013, Rheology in
Pharmaceutical Formulations-A Perspective, Journal of Developing Drugs, Volume 2,
Issue 2. Available at: http://www.omicsgroup.org/journals/rheology-in-pharmaceutical-formulationsa-
perspective-2329-6631.1000108.pdf
2. Tharwat F. Tadros, 2013, Emulsion Formation, Stability, and Rheology, Wiley online
journals. Available at: http://www.wiley-vch.de/books/sample/3527319913_c01.pdf
3. Anon, 2014, Newtonian and non-Newtonian Fluids, Online. Available at:
http://www.msubbu.in/ln/fm/Unit-I/NonNewtonian.htm
4. Dr. Sandle, 2013, Container-Closures for Pharmaceutical Preparations, Online. Available
at:
http://www.mypharmacareers.com/pharmajournal/articles/container_closures_for_pharma
ceutical_preparations.html
5. Guidance for Industry, 1999, Container Closure Systems for Packaging Human Drugs
and Biologics, Online Book. Available at:
http://www.fda.gov/downloads/Drugs/Guidances/ucm070551.pdf