PHARMACEUTICAL EMULSIONS Sudip Das, MPharm, PhD References: Remington – The Science and Practice of Pharmacy, 17th, and 22 nd ed. Martin's Physical Pharmacy, Sinko, 6 th ed. Physicochemical Principles of Pharmacy, A T Florence and D Attwood, 4th Ed Pharmaceutics: The Science of dosage form design, 4th ed., Aulton & Taylor Media files Learning Objectives On completion of these topics the students should be able to Define emulsions and identify main types of emulsions Discuss factors affecting the stability and methods that may be used to stabilize emulsions Be capable of preparing stable emulsions Describe the clinical importance and mechanisms of destabilization of pharmaceutical emulsions. Apply the knowledge of emulsification to improve bioavailability/efficacy of drugs Definition A dispersed system containing at least two immiscible liquid phases. Size of the dispersed phase is normally 0.1 - 100 m. Emulsions MUST contain three major components Dispersed phase – internal or discontinuous phase Dispersion medium – external phase or continuous phase Emulsifying agent Purpose/Advantages of Emulsion and Emulsification Homogeneous mixture of two or more immiscible liquids Masking of objectionable taste and odor Permits administration of liquid drug in the form of small globules - increase of absorption compared to bulk Elegant preparation Water washable drug bases for cosmetic purposes Intravenous administration of lipid nutrients (particle size < 100 nm) Cost effective over using a single-phase lipid preparation - lipid and lipophilic solvents are expensive What about disadvantages?? Some Commercial Products Clevidipine butyrate emulsion ( Cleviprex®) – IV (indicated for the reduction of blood pressure when oral therapy is not feasible or not desirable) Cyclosporine ophthalmic emulsion (Restasis®) - ocular Cyclosporin self-microemulsifying emulsion (Neoral®) - oral Parenteral fat emulsion (Intralipid®) - IV Emulsion of propofol (Diprivan®) – IV anesthetic Emulsion of diazepam (Dizac®) – IV for status epilepticus and severe recurrent convulsive seizures (off market) Emulsion of perfluorodecalin (Fluosol®) - IV oxygen carrier in blood substitute preparations. Used to prevent myocardial ischemia during percutaneous transluminal coronary angioplasty FYI: What are emulsions? - Some important PK/PD of IV emulsions Copyright rules apply 1 of 20
Plasma half-lives are short o Clevidipine butyrate – 15 minutes o Propofol – 1.5 – 5 hrs. (follows a three-phase elimination) Formation of Emulsion: “Emulsion is a thermodynamically semi-stable system” Why?
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- Emulsion, C. Emulsion