Pharmaceutical Science: Creams, Ointments, Gels
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Questions and Answers

Which emulsifier is known to form a swollen lamellar structure?

  • Triethanolamine (correct)
  • NaOH
  • KOH
  • None of the above

    • Creams can experience creaming and coalescence similar to liquid emulsions.

    False

    Name one factor that affects the rheological properties of creams.

    Concentration of emulsifiers

    At low concentrations of emulsifiers, creams have a high proportion of free ______.

    <p>water</p> Signup and view all the answers

    Match the term with its corresponding description:

    <p>Viscoelastic multicomponent gel = Cream phase where oil droplets are immobilized Swollen lamellar structure = Structure formed by triethanolamine Liquid emulsions = Phase with free-moving oil droplets Rheological stability = Consistency of cream over time</p> Signup and view all the answers

    Which of the following is a component of Emulsifying Ointment?

    <p>Liquid Paraffin</p> Signup and view all the answers

    Sodium stearate is an example of a lipophilic surfactant.

    <p>False</p> Signup and view all the answers

    What does HLB stand for in the context of emulsifiers?

    <p>Hydrophilic-Lipophilic Balance</p> Signup and view all the answers

    The primary fatty alcohol used in emulsifying ointment is _____.

    <p>Cetostearyl Alcohol</p> Signup and view all the answers

    Match the emulsifiers with their characteristics:

    <p>Sodium Lauryl Sulphate = Water soluble surfactant Cetyl Alcohol = Fatty alcohol Cetrimide = Ionic surfactant Glyceryl Monostearate = Non-ionic surfactant</p> Signup and view all the answers

    Which ingredient is NOT part of the Aqueous Cream formulation?

    <p>Liquid Paraffin</p> Signup and view all the answers

    Fatty acids are typically used in small quantities as emulsifiers.

    <p>False</p> Signup and view all the answers

    Which factor contributes to the stability of creams at high temperatures?

    <p>Interfacial tension</p> Signup and view all the answers

    Coalescence in emulsions leads to an increase in droplet size.

    <p>True</p> Signup and view all the answers

    What type of network is formed by lipid amphiphiles upon contact with water?

    <p>α-Crystalline gel-network phase</p> Signup and view all the answers

    The process by which droplets are immobilized in creams is known as _______.

    <p>gel network structure</p> Signup and view all the answers

    Match the following forms of long chain alcohols with their characteristics:

    <p>α-form = Stable over a narrow temperature range β-form = Exists at lower temperatures γ-form = Can coexist with β-form at room temperature Mixed form = Reduces transition temperature of lipid amphiphiles</p> Signup and view all the answers

    Which type of stabilization is attributed to the presence of charge repulsion?

    <p>Electrostatic stabilization</p> Signup and view all the answers

    The self bodying effect describes emulsions becoming less viscous at high concentrations.

    <p>False</p> Signup and view all the answers

    What type of crystalline forms can cetyl or stearyl alcohol exist as at room temperature?

    <p>Both β- and γ-crystalline forms</p> Signup and view all the answers

    α-Crystalline forms are created when no surfactants are present.

    <p>False</p> Signup and view all the answers

    What is the significance of emulsifiers in the gel network structure?

    <p>They provide stability by interacting with water.</p> Signup and view all the answers

    Cream stability can be influenced by _______ and _______ interactions in water.

    <p>emulsifier , polymer</p> Signup and view all the answers

    What is the approximate temperature range for the gel liquid transition temperature (Tc) for cetostearyl alcohol?

    <p>40-50°C</p> Signup and view all the answers

    Which theory explains the stabilization of creams via the structure of the external phase?

    <p>Lamellar gel network theory</p> Signup and view all the answers

    The transition from α-crystalline gel to liquid crystalline form occurs when heated to _____ degrees Celsius.

    <p>Tc</p> Signup and view all the answers

    Match the phases with their characteristics:

    <p>α-Crystalline Gel = Swells significantly with surfactants Liquid Crystalline = Less swollen form α-Hydrate = Waxy crystalline hydrates Swollen Gel Phase = Occurs below Tc</p> Signup and view all the answers

    What effect do surfactants have on α-crystalline forms when mixed?

    <p>They cause significant swelling</p> Signup and view all the answers

    The viscosity of creams decreases when water is trapped in the gel structure.

    <p>False</p> Signup and view all the answers

    What state do creams adopt during the manufacturing process due to high temperatures?

    <p>Liquid crystalline state</p> Signup and view all the answers

    The gel liquid transition temperature is sometimes referred to as the _____ temperature.

    <p>setting</p> Signup and view all the answers

    What happens to α-crystalline gel upon cooling below Tc?

    <p>It reverts back to the swollen gel phase</p> Signup and view all the answers

    What stabilizes the dispersed oil droplets in creams?

    <p>Monolayer emulsifier film and charge</p> Signup and view all the answers

    The α-crystalline gel phase consists of fatty alcohol and surfactant separated by interlamellar fixed water.

    <p>True</p> Signup and view all the answers

    What happens to the PEO chain at high temperatures shortly after preparation?

    <p>The PEO chain is less well hydrated and no gel phase is formed.</p> Signup and view all the answers

    Electrolytes will compress the electric diffuse double layer, and reduce the __________ between adjacent bilayers.

    <p>repulsion</p> Signup and view all the answers

    Match the following emulsifier mixtures with their characteristics:

    <p>Fatty alcohol with ionic emulsifiers = Extensive swelling and electrically charged Fatty alcohol with PEO surfactants = Steric stabilization and hydration-dependent viscosity Fatty acid mixed emulsifiers = Polymorphisms and non-greasy residue Fatty alcohol with alkali = Partial neutralization for stearate cream</p> Signup and view all the answers

    What effect does the addition of electrolytes have on the viscosity of the lamellar gel-network phase?

    <p>Reduces viscosity</p> Signup and view all the answers

    The bulk continuous phase of creams includes solely fixed water.

    <p>False</p> Signup and view all the answers

    What is the appearance of vanishing cream upon application?

    <p>It appears to vanish, leaving a non-greasy residue.</p> Signup and view all the answers

    The water layer in fatty alcohol with ionic emulsifiers is __________ thicker than the carbon layer.

    <p>10 times</p> Signup and view all the answers

    Match the following phases with their characteristics related to swelling:

    <p>α-Crystalline gel phase = Significant swelling α-Crystalline hydrate = Limited swelling Bulk continuous free water = No swelling</p> Signup and view all the answers

    Study Notes

    Pharmaceutical Science and Formulation I: Creams, Ointments, and Gels

    • This lecture series covers the formulation of creams, ointments, and gels.
    • The presenter is Dr. Jihong Han, room HNB 0.54b, [email protected].

    Outline

    • Part 1: General aspects of creams: This section covers general information about creams.
    • Part 2: Structure of creams and gel network theory: This part explores the structure of creams.
    • Part 3: Attributes and manufacture of creams: This section details the attributes and manufacturing process of creams.
    • Part 4: Ointments and gels: This segment focuses on the formulation and characteristics of ointments and gels.

    Introduction

    • Historically, topical semisolids were primarily developed based on cosmetic considerations, not scientific principles.
    • Examples of topical semisolids included: creams, ointments, gels, and pastes.
    • These preparations often exhibit non-Newtonian flow properties, such as plastic, pseudoplastic, or thixotropic behavior.
    • The traditional distinctions between creams and ointments were usually not well-defined.
      • These terms often used interchangeably in practice rather than following scientific definitions.
      • An example is Hydrous Ointment (BP) used interchangeably with Oily Cream.

    Creams - General

    • Creams are semi-solid preparations intended for external use.
    • Aqueous creams are oil-in-water (o/w) emulsions.
      • The aqueous phase structure is often influenced by materials such as clay particles and polymers, creating a lamellar gel network.
      • These are generally miscible with skin secretions.
    • Oily creams are water-in-oil (w/o) emulsions.
    • Some other bases with complex matrix-like structures are also called "creams" due to their appearance and feel (but not scientifically).

    Hydrophilic Creams

    • Aqueous phase is the continuous phase in o/w emulsions.
    • Features include non-greasy texture and water wash ability.
    • Non-occlusive, meaning they do not block the skin from absorbing or releasing moisture.
    • The continuous aqueous phase evaporates, increasing the concentration of the drug in the remaining layer, which is beneficial for topical drug administration.

    Creams - Emulsifiers

    • Common emulsifiers include lipophilic amphiphiles (like fatty alcohols and fatty acids) and water-soluble surfactants (ionic or non-ionic).
    • The HLB (Hydrophilic-Lipophilic Balance) concept is important to consider. HLB can be used to determine how hydrophilic or lipophilic a surfactant is.

    Ready Made Creams Mixtures

    • Some examples of ready-made cream mixtures include emulsifying ointment (BP), emulsifying wax, white soft paraffin, and liquid paraffin.
    • Specific compositions and quantities of ingredients for ready-made cream mixtures are noted.
    • Aqueous cream (BP) is given as a formulation example.

    Part 2: Structure of creams and gel network theory

    • Several theories on cream stability are available in the literature.
    • Relevant factors in cream stability (high temperatures): droplet size, creaming, coalescence, interfacial energy/tension, interfacial film of emulsifiers, charge repulsion, and steric stabilization.
    • The external phase, typically a mixture of water and emulsifiers, can form structures that immobilize the components, leading to more stable creams.

    Gel network structure

    • External phases in creams often form a structure in order to stabilize the oils.
    • Excess lipid amphiphiles are used beyond the amount that can be absorbed in the interface for better stability.
    • Factors and mechanisms associated with crystalline gel network phases, the role of emulsifier interactions, and the impact of crystal structure on cream stability are studied.

    Interaction of emulsifiers in water

    • Long chain alcohols can exist in different polymorphs (alpha, beta, and gamma forms) depending on conditions.
    • The transition temperature of the lipid amphiphiles can be reduced when mixed; at room temperature, some mixtures may exist in multiple crystalline polymorphs.
    • Formation of a-crystalline is important for forming liquid crystalline and swollen crystalline phases.
    • The factors affecting the formation and stability of crystalline networks and their role in stabilizing oil droplets in creams are studied.
    • The interlamellar water layer and the role of the crystalline structure in retaining water

    Lamellar gel network theory

    • The alpha-crystalline forms exhibits limited swelling.
    • The addition of surfactants to the system helps swell significantly and form a viscoelastic alpha-crystalline gel phase or a liquid crystalline phase depending on temperature and concentration.
    • The crystalline gel network has been shown to trap and immobilize oil droplets, which is favorable for stabilizing the cream.

    Interaction of emulsifiers in water (contd.)

    • Alpha-crystalline forms waxy crystalline hydrates with limited swelling in water.
    • In the presence of surfactants (alcohol to surfactant molar ratio between 10 to 30:1), it forms a-crystalline gel phase, which is viscoelastic.
    • Alpha-crystalline gel phase changes to a less swollen liquid crystalline form upon heating to the gel liquid transition temperature. These conditions can lead to a change in viscosity.
    • Cooling often restores the swollen gel phase. The transition temperature is sometimes referred to as the "setting temperature."

    Microstructure of creams

    • Dispersed oil droplets are stabilized by a monolayer emulsifier film and charge interactions.
    • Viscoelastic continuous phase is formed, sometimes characterized by crystalline hydrates and less-swollen liquid crystalline areas/water. The bulk continuous phase often consists of free water.

    Specific emulsifier mixtures

    • Fatty alcohols with ionic emulsifiers, the water layer in the structure is significantly thicker than the carbon layer. Electrostatic charging may play a role.
    • Addition of electrolytes may compress the electric double layer and reduce repulsion between bilayers in the structure, also affecting viscosity.
    • Fatty alcohols with polyoxyethylene (PEO) surfactants: swelling is due to the hydration of the PEO chain as well as steric stabilization.
    • The behavior of PEO surfactants changes with temperature, with better hydration at lower temperatures and a fluid phase at higher temperatures.

    Specific emulsifier mixtures (contd.)

    • Fatty acid mixed emulsifiers: Polymorphisms can occur, and some systems can "vanish", or leave behind a residue on the skin post application.
    • The neutralisation of fatty acids with alkali (e.g., Triethanolamine) can form swollen lamellar structures with a twisted ribbon form.

    Part 3: Attributes and manufacture of creams

    • The physical attributes, such as overall consistency and appearance, of creams are considered.
    • Factors influencing these features include the thickness of interlamellar water layers, the relative proportions of different phases, phase stability at varied temperatures, and batch-to-batch variation.

    Liquid Emulsions vs Creams

    • Oil droplets in liquid emulsions tend to be mobile and can move freely.
    • Creams contain an immobilized oil phase in a gel. This immobility is key to creaming or coalescence resistance

    Self-bodying action

    • The concentration of the emulsifier mixture in a cream significantly impacts rheological properties.
    • Low concentration mixtures are fluidic but contain a high proportion of free water.
    • High concentration mixtures are more structured, with a reduced proportion of free water and higher viscosity.

    Manufacture of creams

    • Cream production is more elaborate than liquid emulsion production due to the intricacies of continuous phase structure.
    • Scaling-up of cream production from small-scale labs to large-scale production requires careful control, as the equipment and conditions affect the product's microstructure.
    • Temperature cycling parameters, equipment use, and specific equipment effects are different, affecting the dynamics of the process.

    Terbinafine 1% and Canesten Creams

    • Detailed information on composition, application, and indications are provided for two specific creams.
      • Terbinafine is included as one of the specific examples where data are given.
      • Active ingredients, percentages of these ingredients, excipients, and specific manufacturers/suppliers are noted.

    Ointments

    • Ointments are single-phase bases that can include solids or liquids.
    • They are highly viscous and occlusive (preventing water loss from the skin), creating emollient, protective, and therapeutic effects.
    • Medicaments can be dissolved or dispersed within the ointment base.
    • Hydrophobic ointments absorb small amounts of water, typically utilizing bases like paraffins, vegetable oils, animal fats, and waxes.
    • Water-emulsifying ointments can absorb more water leading to forming water-in-oil or oil-in-water emulsions.
    • Hydrophilic ointments are miscible with water, using bases such as polyethylene glycols (e.g., macrogols).

    Preparation of ointments

    • The ointment bases are melted above their melting points.
    • The excipients and the drug are mixed with the melted base.
    • The mixture is cooled, and special equipment like rollers can help produce a smooth product free from separation of components.

    Aciclovir Agepha 30 mg/g eye ointment

    • An example of an ointment, with its active ingredient, usage, and excipients listed.

    Gels

    • Semi-solid systems held together by colloidal particles that form a three-dimensional (3D) network using water as a medium.
    • Gels often contain a high percentage of water.
    • Gels typically thin out (lower viscosity) when subject to shear stress but return to original condition over time, a property called thixotropy

    Types of Gel

    • Gelation of lyophobic colloids and lyophilic colloids (polymers) are described. Different types of gel-forming mechanisms and factors are described, such as covalent bonds, hydrogen bonds, and van der Waals forces.

    Gelling Agents

    • Classification of gelling agents (semi-synthetic, natural, and synthetic), including specific examples.
    • Formulation and concentration factors are explored to highlight properties associated with clarity and structure.
    • The type of polymer can determine the gelling characteristics (covalent vs. reversible)

    Gelling Temperature (Tg)

    • Factors affecting the gelling temperature of different polymer systems are discussed.
      • Including polymer concentration
      • Effect of temperature on polymer solubility
      • Polymer properties like the formation of micelles and crystal structures.

    Carbomer Mechanisms of uncoiling

    • Carbomer (Polyacrylic acid) mechanisms for the conversion of the molecules (from their acidic to salt form) to manipulate viscosity and the formation of a gel state in the presence or absence of surfactants.
    • The uncoiling process and polymer structure are both explained.
    • "Aulton's Pharmaceutics" by Michael E. Aulton and David Taylor (4th or 5th edition) is recommended reading for further study.

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    2023-2024 Creams and Ointments - Tagged PDF

    Description

    This quiz explores the formulation and characteristics of creams, ointments, and gels as discussed in the Pharmaceutical Science and Formulation I lecture series. Dive into the general aspects, structure, attributes, and manufacturing processes of these topical semisolids. Perfect for students and professionals in pharmaceutical sciences.

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