Ointments and pastes are semisolid dosage forms meant for external application, primarily to the skin. Medicated ointments treat infections, inflammation, and itching while non-medicated versions act as emollients and lubricants. Pastes contain over 50% drug. The choice of ointment base depends on site of application, required drug release rate, drug stability, and effect on viscosity. Bases include hydrocarbons, absorption bases like lanolin and beeswax, water-miscible bases, and water-soluble bases. Hydrogels and gels containing dispersed solids like kaolin are other topical dosage forms. Factors like polymer concentration and molecular weight affect gelation.
dr.deepthikolluru avancements in Ophthalmic products pptDeepthiKolluru1
advantages, product formulation of conventional opthamicpreapartions and introduction to advanced optahlmicproducts like contact lenses, ocular inserts, collagen sheilds.
it is a complete overview on ophthalmic dosage form. beginning from anatomy and physiology of eye with drug absorption mechanism including all factors to formulation considerations and evaluation of the products i.e. eye drops and eye ointment & the evaluation tests. it will help you make the concepts clear about ophthalmic drug deliveries.
the all the content in this profile is completed by the teachers, students as well as other health care peoples.
thank you, all the respected peoples, for giving the information to complete this presentation.
this information is free to use by anyone.
dr.deepthikolluru avancements in Ophthalmic products pptDeepthiKolluru1
advantages, product formulation of conventional opthamicpreapartions and introduction to advanced optahlmicproducts like contact lenses, ocular inserts, collagen sheilds.
it is a complete overview on ophthalmic dosage form. beginning from anatomy and physiology of eye with drug absorption mechanism including all factors to formulation considerations and evaluation of the products i.e. eye drops and eye ointment & the evaluation tests. it will help you make the concepts clear about ophthalmic drug deliveries.
the all the content in this profile is completed by the teachers, students as well as other health care peoples.
thank you, all the respected peoples, for giving the information to complete this presentation.
this information is free to use by anyone.
Explaining creams as pharmaceuticals, knowing the difference between lotions , creams, ointments and emulsions.
# Cosmetics # pharmacy # dosage forms # formulation
his presentation delves into the formulation, advantages, and applications of semisolid dosage forms, including creams, ointments, and gels. Learn about their unique properties, manufacturing processes, and considerations for drug delivery. Whether you're a student or a pharmaceutical professional, this presentation offers valuable insights into this essential aspect of medication delivery.
The presentation contains brief explanation about the Emollients, its types with detailed examples. Brief classification of Rheological additives is also presented along with the applications in cosmeceuticals.
hard and soft gelatin capsule shell manufacturing. preparation of shell fluid, preparation of fill material and manufacturing process. machineries and equipment for capsule manufacturing. stability and quality control
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
1. Ointments & Pastes
• Pharmaceutical ointments termed unguents are semisolid systems
that are applied externally, primarily to the skin and also to mucous
membranes.
• Medicated ointments are used for the treatment of infection,
inflammation and pruritus.
• Non-medicated ointments are used as emollients and lubricants.
• Pastes are composed of ointment base that contain a high
concentration of dispersed drug ( > 50% w/w)
• The viscosity of pastes are greater than that of ointments.
2. Factors determining the choice of ointment base
1. The site of application.
2. The required rate of drug release.
3. The chemical stability of drug.
4. The effect of the therapeutic agent on formulation viscosity.
3. Types of base for ointments and pastes
1. Hydrocarbon bases.
2. Absorption bases.
3. Water-miscible/removable bases.
4. Water-soluble bases.
4. Hydrocarbon bases – Paraffins
• Non-aqueous having the properties:
• Emollients , prevents water loss by forming occlusive film
• Excellent retention on the skin.
• Predominantly hydrophobic, so difficult to remove from the skin and also
difficult to be applied on the moist surface.
• Not more than 5% of water could be incorporated with careful mixing.
• Chemically inert.
Hard paraffin, white/yellow soft paraffin, liquid paraffin,
microcrystalline wax.
5. • Hard paraffin is white or colourless microcrystals wax. Melting point
47 – 65. used to enhance the rheological properties of ointment base.
• White/yellow soft paraffin is semisolid, consists of hydrocarbons
derived from petroleum. Melting point 38 – 60 and can be used as an
ointment base without additional components.
• Liquid paraffin; usually formulated with soft paraffin to achieve the
required viscosity. It requires incorporation of antioxidant.
• Microcrystalline wax ; semisolid used to enhance the viscosity of
ointments and creams. It has greater physical stability and when
provided to liquid paraffin it reduces the bleeding of liquid
component.
6. Absorption bases
• Contain significant amount of an aqueous phase. May be:
• Non-aqueous formulation to which an aqueous phase may be added to
produce water in oil emulsion ( non-emulsified bases).
• Water in oil emulsions that can facilitate the incorporation of an aqueous
phase without inversion or cracking.
• They are still difficult to be removed by washing.
Non-emulsified bases; lanolin (wool fat), wool alcohols, beeswax.
Water in oil emulsions; hydrous lanolin
7. • Non-emulsified bases are hydrophobic formulations to which water
may be added. Good spreading properties. They are emollients. They
are composed of 1/ paraffins 2/ a sterol based emulsifying agent.
[lanolin ( wool fat), lanolin alcohols ( wool alcohols) and beeswax].
• Lanolin is mixed with vegetable oil or paraffin to produce an ointment
base that can absorb twice of it weight of water to produce water in
oil emulsion. The usual concentration of lanolin in simple ointment is
5 -10 % w/w.
• Wool alcohols is added to a mixture of hard and soft paraffin to
produce the required consistency. Inclusion of wool alcohol 5% w/w
results in a 300% increase in the concentration of water that may be
incorporated in paraffin bases.
• Bees wax consists of esters of aliphatic alcohols C24 – C36 even
numbers . Combined with paraffins to produce non-emulsified bases.
8. Absorption bases – water in oil emulsion.
• Excipient used in this ointment base is hydrous lanoline which is a
mixture of lanoline and water 25 -30 %.
• It is incorporated into paraffins and oils that can incorporate the
subsequent addition of aqueous phase.
• Oily cream BP is water in emulsion ointment base that is composed of
wool alcohol and water 50% each.
9. Water-miscible / removable bases
• Used to form water in oil emulsion for topical application.
• They are able to accommodate large volumes of water ( edema – wounds).
• They are not occlusive.
• Easily to be washed and removed out.
• They are aesthetically pleasing.
10. BP water-miscible/removable bases:
1. Emulsifying ointment
2. Cetrimide emulsifying ointment.
3. Cetomacrogol emulsifying ointment.
• Each containing liquid paraffin20%, white soft paraffin 50% and
emulsifying wax 30%.
• Types of emulsifying wax:
• Anionic emulsifying wax.
• Non-ionic emulsifying wax.
• Cationic emulsifying wax.
12. Water-soluble bases
• They are non-greasy, miscible with the excudates and compatible with
majority of therapeutic agents.
• Prepared by mixing Polyethylene glycol 400 and polyethylene glycol
4000 in a ratio of 60%, 40% respectively then heat and controlled
cooling.
• Used to incorporate solid therapeutic agent.
• Incorporation of 5% or more water will liquidify the base.
• To incorporate up to 25% aqueous phase, PEG 400 may be replaced
by stearyl alcohol.
13. Additional / alternative solvents
• Liquid silicon: used in barrier ointments due to its water-repellent.
• Vegetable oils: may be used either to replace mineral oils or to enhance
the emollient properties ( arachis oil, cocanut oil).
• Organic esters: isopropyl myristate is used to enhance the spreadability
properties and enhance drug dissolution within the ointment base.
14. Preservatives
• Ointments / pastes that do not contain water do not require
preservative.
• Preservatives for those containing water:
Phenol 0.2-0.5%, chlorocresol 0.075 – 0.12%
Benzoic acid and its salts 0.1 – 0.3%
Methyl parabens and propyl parabens 0.2 -0.3%
• Concentration should equal or exceed the MIC
Antioxidants
- Lipophilic
- Hydrophilic
15. Manufacture of ointments & Pastes
• Dispersal of the powdered therapeutic agent into the pre-heated
hydrocarbon base using mechanical mixer.
• Hydrophobic component and hydrophilic components are dissolved
separately in their liquid phases.
• The two phases are maintained at 70 C then mixed together either
simultaneously or by adding the aqueous phase to the non-aqueous
phase.
16. Lotions
• May be formulated as solution or suspension.
• It contains the therapeutic agent and
+ alcohol as co-solvent and coolant.
+ humectants to retain the moisture on the skin after application (
Glycerol).
+ vehicle purified water with or without buffer.
+ preservative.
+ component to stabilize the suspended therapeutic agents.
17. Liniments
• Alcohol-based liniment: act as counterirritants and rubefacient causing
reddening of the skin and may act to increase the penetration of the
drug through the skin. This will provide cooling effect; soap liniment.
• Oil-based liniment: employed in conditions of massage. Oil used is
arachis oil and cottonseed oil ; camphor liniment, methyl salicylate
liniment.
• Generally no other excipients are used.
18. Collodions
• Collodions are solutions of pyroxylin ( nitrated cellulose predominantly
cellulose tetranitrate), castor oil and colophony dissolved in an organic
solvent composed of alcohol and ether. Normally applied to the skin by
brush and after evaporation of the solvent will form occlusive film.
• Collodions may contain therapeutic agents as colliodion and salicylic
acid and collodion.
• Collodion is a solution of pyroxylin in 3 ether + 1 alcohol. This will form
firm film and may render flexible by adding 2% camphor and 3% castor
oil.
• Salicylic acid collodion is a solution of salicylic acid 10% in flexible
collodion and used for the treatment of warts.
19. Advantages of ointments and pastes
• Spreadability.
• Occlusive
• Lubrication and emollient
• Release of drug
• Hydrophobicity
• Pastes………….porosity
• Pastes opaque
• Stability of drug
• Cooling effect
20. Disadvantages
• Greasy
• Pastes thick
• Staining
• Liniment not applied to broken skin
• Exuding sites
• Limited solubility of drug in base
• Pastes to hair
22. Gels – description
• The vehicle is continuous and interact with the colloidal particles
within the 3 dimensional network formed by the bonds created
between the adjacent particles.
• The vehicle may be aqueous, hydro-alcoholic, alcoholic or nonaqeous.
• Colloidal particles may be dispersed solids; kaolin, bentonite.
• Colloidal particles may be dispersed polymers.
• Xerogels are gels in which the vehicle had been removed leaving a
polymer films.
23. Main categories of pharmaceutical Gels
Categorization was based in the nature of the three dimensional network
of particles.
• Dispersed solid gels.
• Hydrophilic polymer gels
24. Dispersed solid gels.
• When dispersed particles undergo flocculation throughout the system, a
continuous solid particle network is established, with the liquid vehicle
dispersed in the void volume between the particles.
• The nature of the interaction between the particles in the network may
be van der Waals e.g Aluminium hydroxide gel .
• OR electrostatic bonding e.g Kaolin, bentonite, Al.Mg silicate.
• The particles exhibit plate-like crystal structure with electronegative
charges at the face and electropositive charges at the edges.
• The bonding strength between the particles is weak which can be
broken by shaking resulting in liberation of individual particles. On
removal of stress the rheological properties return. This recovery is
time-dependent and termed thioxytropy.
25. Hydrophilic polymer gels
• Dispersion of hydrophilic polymer within appropriate aqueous vehicle.
• There are two types:
1- types 1 gels.
2- type 2 gels.
26. 1- types 1 gels.
• Termed as hydrogel.( type 1 chemical)
• The interaction between the polymer chain is covalent and is mediated by
molecules that cross-link the adjacent chains ( cross-linker).
• Example of a cross-liked hydrogel and monomer is hydroxyethylmethacrylate
and the cross- linker ethyleneglycol dimethacrylate.
• It has the ability to absorb a considerable mass of aqueous fluid whilst still
retaining the3D structure.
• It exhibit robust mechanical structure being resistant to fracture up to 1 kpa.
• Having excellent flexibility
• Hydrogels in which the aqueous been removed is termed xerogels. It is brittle
and the aqueous phase is used as plasticizer.
27. • Type 1 gels do not exhibit flow when exposed to and applied stress
due to inability of the stress to destroy the covalent bonds.
• This elastic properties enable the energy utilized to be stored and
utilized after removal of stress to return to equilibrium.
• Hydrogels are used in wound dressings, as lubricants coating in
urethral catheters and as soft contact lenses.
• Used for the controlled delivery of therapeutic agents at the site of
implantation.
28. 2- type 2 gels.
• The bonds are either hydrogen bond, ionic association or van der
Waals interactions. These bonds are weaker bonds. So, interactions
between polymer chains are reversible.
• Application of stress can result in flow. So it shear – thinning system.
• Being pseudoplastic, on removal of stress, the intermacromolecules
bonds are reformed.
• This type 2 gels are used in formulations:
- Cellulose derivatives.
- Polysaccharides from natural origin.
- Polyacrylic acid
30. Polysaccharides from natural origin.
• Carrageenan derived from red seaweed. They are lambda, iota and kappa.
Which differ in the location of sulphate group and absence of
anhydroglactose. Kappa carrageenan exhibit excellent gelling properties. 0.3
– 1% w/w.
• Alginic acid / sodium alginate derived from algae. addition of calcium ions
to aginate solution will result in a viscous gel. It is incompatible with basic
drugs.
• Poly ( acrylic acid); produced following polymerization of acrylic acid and
cross-linking with allyl sucrose or ally ethers of pentaerythritol.0.5 -2% w/w
polyacrylic acid neutralized with an appropriate base is used. It is
incompatible with basic therapeutic agents. Its viscosity is adversely
affected by medium and high concentration of electrolyte.
31. Factors affecting gelation of type 2 gels
1. Concentration of hydrophilic polymer.
2. Molecular weight of the polymer.
3. Nature of the solvent.
4. pH of the solvent.
5. Ionic strength of the solvent phase.
6. Temperature.
7. Ionic gelation.
32. Concentration of hydrophilic polymer.
• At low concentrations, the hydrophilic polymer exhibit
Newtonian flow due to the limited number of polymer-polymer
interactions.
• As the concentration increases, the number of polymer-polymer
interactions increases and at a definite concentration, the flow
properties become non-Newtonian --- this the gel point.
• Further increase lead to increase in the junction zones and
increase resistance to applied stress.
• Therefore, the physiochemical and rheological properties of a
pharmaceutical gel may be readily manipulated by altering the
concentration of hydrophilic polymer.
33. Molecular weight of the polymer
• As the molecular weight of the hydrophilic polymer increases at a
definite concentration, there are a greater number of available sites
on the polymer chains that may engage in the polymer-polymer
interactions.
• As a result the viscosity of the formulation increases.
34. Nature of the solvent.
• In good solvents, the chains of the polymer exist in the expanded state.
• In poor solvent, the polymer chain exist in coiled state.
• The viscosity of the polymer solution depend on the expansion of the
polymer chains.
• Therefore, the physiochemical properties of the gel are dependent on
the solvent system into which the hydrophilic polymer is dissolved.
• In poor solvents gelation will not occur.
35. pH of the solvent.
• The pH affects the ionization of acidic or basic polymers which in turn
affects the expansion state of the polymer.
• In non-ionized state, acidic and basic polymers exist in a coiled state
and gelation does not occur.
• The rheological properties of ionic polymers are optimal with range of
pH values at which maximum expansion of chains occur.
• The rheological properties of non-ionic polymers are unaffected by
the pH of the solvent, usually pH 4 – 10.
36. Ionic strength of the solvent phase.
• Presence of high concentration of electrolytes affects both ionic and
non-ionic polymers.
• Non-ionic polymers may be salted out of solution due to desolvation
of the polymer chains.
• At low concentration of electrolyte , shielding of the charge on the
ionic polymer will occur, this will reduce the capacity of the polymer
to interact with solvent resulting in compromised gel properties.
• If the concentration of the electrolyte is too high, salting out of ionic
polymer will result.
37. Temperature
• Methyl cellulose and hydroxypropyl cellulose have been reported to
undergo gelation at elevated temperature 50 – 60 ˚C . this transition
has a limited biological relevance.
• Poly(oxyethylene)-poly(oxypropylene)block co-polymers undergo
thermal transition at < 37˚C range. At temperature below this
transition ( sol-gel) temperature Tsol/gel , the solution of the polymer
undergo Newtonian flow and low viscosity ( sol state). Above this
Tsol/gel is converted into gel with pronounced elasticity and viscosity.
• In solution at temperature below Tsol/gel and above the critical micelle
concentration , the polymer exists in a micellar state, elevation of
temperature above Tsol/gel , the micelles aggregate resulting in a gel.
On lowering the temperature will result in deaggregation of micelles
and reemergence of sol.
• This lead to their use as drug delivery system. Within the oral cavity
and rectum.
38. Ionic gelation
Certain hydrophilic polymers undergo gelation in the presence of
inorganic metal ions.
Polyvinyl alcohol polymers, gelation occur in the presence of borate ,
permanganate giving a gel of excellent mechanical strength due to
the borate anion-mediated cross-link. ( toy Kid)
Gelation of alginic acid occur in the presence of Mg, Ca, and Al ions.
39. Formulation of a pharmaceutical gels
1. Choice vehicle.
2. Inclusion of buffer.
3. Preservatives.
4. Antioxidants.
5. Flavours/ sweetening agents.
6. Colours.
40. Choice of vehicle
• Purified water is the normally used in formulation of pharmaceutical gel.
Co-solvent may be used as alcohol, propylene glycol, glycerol, poly
ethylene glycol 400 to enhance the solubility of the therapeutic agent
and to enhance permeation across the skin ( ethanol).
If the drug has poor chemical stability and/or poor solubility in water,
pharmaceutical gel may be formulated using propylene glycol, glycerol,
polyethylene glycol 400 and poly acrylic acid.
In these systems gelation is facilitated by hydrogen bonding between
hydroxyl and carboxylic acid groups and this results in:
1. expansion of pendant groups on the polymer chain.
2. Non-covalent cross-linking of adjacent polymer chain.
41. Inclusion of buffer
• Citrate and phosphate buffer may be included in aquous or
hydroalcoholic gels to control the pH of the formulation.
• The solubility of buffer salts is decreased in hydroalcoholic-based
vehicles.
42. Preservatives
• Same as ointments.
• It should be noted that parabens, phenolics interacts with the
hydrophilic polymers used to prepare gels, therby reducing the
concentration of free ( antimicrobially active ) preservative. Thus, the
concentration of these preservatives should be increased.
43. Antioxidants
• Used to increase the chemical stability that are prone to oxidative
degradation.
• Selection of antioxidant depend on the nature of the vehicle used.
• Because majority of gels are aquous-based, water-soluble
antioxoidant is used.( sodium metabisuphite, sodium formaldehyde
sulphoxylate are commonly used)
45. Manufacturing of pharmaceutical gels
• Water soluble components are dissolved in the vehicle in a mixing
vessel with mechanical stirring.
• The hydrophilic polymer is added to the stirring mixture slowly to
prevent aggregation.
• Stirring is continued until complete dissolution of the polymer.
• Excessive stirring results in entrapment of air.
• Vacuum may be applied to remove the entrapped air.