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What is the significance of poorly soluble drugs forming an intermolecular complex with soluble materials?
What is the significance of poorly soluble drugs forming an intermolecular complex with soluble materials?
It improves their solubility, allowing for better absorption and effectiveness.
Explain why most complexes are considered macromolecular and inactive.
Explain why most complexes are considered macromolecular and inactive.
They are often too large to cross lipid membranes and remain inactive until dissociated into smaller, active molecules.
How do cyclodextrins improve the properties of poorly soluble drugs?
How do cyclodextrins improve the properties of poorly soluble drugs?
They create inclusion complexes that enhance solubility by encapsulating the drug within their hydrophobic interior.
What is a common method to increase the aqueous solubility of poorly soluble acids and bases?
What is a common method to increase the aqueous solubility of poorly soluble acids and bases?
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List two uses of nonaqueous solutions in pharmaceuticals.
List two uses of nonaqueous solutions in pharmaceuticals.
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What are fixed oils, and provide an example of their use in pharmaceutical preparations.
What are fixed oils, and provide an example of their use in pharmaceutical preparations.
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How do polyhydric alcohols function as solvents in pharmaceutical products?
How do polyhydric alcohols function as solvents in pharmaceutical products?
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Discuss the role of Dimethylsulfoxide (DMSO) in drug formulations.
Discuss the role of Dimethylsulfoxide (DMSO) in drug formulations.
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Why is ethyl ether not used internally in therapeutic applications?
Why is ethyl ether not used internally in therapeutic applications?
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Give an example of a miscellaneous solvent and its application in pharmaceuticals.
Give an example of a miscellaneous solvent and its application in pharmaceuticals.
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Study Notes
Complexation
- Poorly soluble drugs combined with soluble materials form soluble intermolecular complexes.
- Most complexes are macromolecular and inactive, unable to cross lipid membranes.
- Complex formation is easily reversible.
- Many complexes aren't water-soluble, contributing to prolonged drug release.
- Example: Polyvinylpyrrolidone (PVP) plus iodine improves iodine's aqueous solubility.
- Another example: Cyclodextrins are a series of glucopyranose units forming hollow cylinders (conical shape).
- The inside of cyclodextrins is hydrophobic, while the outer part is hydrophilic.
- Poorly water-soluble drugs can fit inside cyclodextrins, creating a freely water-soluble inclusion complex.
Chemical Modification
- Poorly soluble acids and bases can be converted to salts to improve aqueous solubility.
- Example: Sodium phosphate salts of hydrocortisone, prednisolone, and betamethasone.
Nonaqueous Solutions
Uses
- Stability: Propionate and benzoate esters of testosterone and estradiol provide depot effects.
Choice
- Factors affecting choice include toxicity, irritancy, sensitization, flammability, cost, stability, and compatibility with other excipients.
- Parenteral product choices are further limited.
Classification of Nonaqueous Solvents
1. Fixed Oils of Vegetable Origin
- Non-volatile oils derived from plants, mainly fatty acid esters of glycerol.
- Examples: Almond oil (oleic acid), castor oil (miconazole eye drops), olive oil, sesame oil, maize oil, cottonseed oil, soya oil.
- Used in emulsions and parenterals.
2. Alcohols
- Examples: Ethyl alcohol (external use, cooling, salicylic acid lotion) industrial methylated spirit (IMS), isopropyl alcohol (diclophane/abuse/denaturation).
3. Polyhydric Alcohols/Glycols
- Toxic.
- Examples: Propylene glycol (Diazepam injection, Co-trimoxazole IV Infusion, Chloramphenicol Ear Drops, hydrocortisone ear drops), Peg400 (cosolvent with water/glycerol, water-miscible ointment bases, clotrimazole topical solution).
4. Dimethyl Sulphoxide (DMSO)
- Highly polar.
- Aids drug penetration through skin, mainly for veterinary drugs.
- Example: Idoxuridine for human skin application.
5. Ethyl Ether
- Not used internally (therapeutic).
- Cosolvent with alcohol in some collodions.
- Used in crude drug extraction.
6. Miscellaneous Solvents
- Examples: Isopropyl myristate/isopropyl palmitate (cosmetics) and xylene (ear drops/dissolves ear wax).
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Description
This quiz explores the concepts of drug solubility, complexation, and chemical modification in pharmaceuticals. Learn how poorly soluble drugs can interact with soluble materials to form complexes and how these interactions affect drug release and bioavailability. Real-world examples illustrate these principles in practice.
