Solutions and solubility: Pharmaceutical oral solutions Flashcards
Give an example of an extemporaneous formulation?
Thiamine (Vitamine B1) HCL oral liquid
What s solubility affected by?
- pH
- Temperature (Drug should be in solution at all strengths
List the four different types of solutions?
- Oral solutions
- Oral elixirs
- Oral syrups
- Others including mouthwashes, gargles, rectal solutions and enemas
What are pharmaceutical oral solutions?
These are liquid preparations in which the therapeutic agent and the various excipients are dissolved in the chosen solvent system.
Pharmaceutical solutions for parental administration, or specific formulations require aseptic manufacture. TRUE OR FALSE?
TRUE
What are the advantages of using oral solutions?
- Ease of use/ administration (i.e children or elderly)
- The drug is dissolved and readily available for absorption (As long as the drug is soluble in stomach it will have a greater bioavailability than solid dosage form)
- Modification of taste can improve compliance of bitter tasting drugs.
What are the disadvantages of using oral solutions?
- Stability (cannot be used for drugs that are not stable in water e.g aspirin)
- Limited by the solubility of some drugs (only suitable for drugs with particular solubility profiles)
- Expensive to transport, compared to other dosage forms
- Bulky for patients to carry with them
List the common types of excipients?
- Flavours and colours (sweeteners, dyes)
- Preservatives
- Vehicle (purified water)
- Co-solvents (glycerol, ethanol)
- Solubility enhancing agents (surfactants)
- Viscosity modifiers
- Buffers
Solute-solute interactions are unfavourable but it is entropically viable. TRUE OR FALSE?
TRUE
What are homogenous products?
Product must be in solution throughout all of the drugs shelf life, including excipients as well
Solubility at selected pH may be high , moderate and low. TRUE OR FALSE?
TRUE
What are the factors affecting solubility?
- Crystal form (polymorphism)
- Melting point
- Chemical factors (lipophilicity, ability to ionise)
- pH will affect the solubility of acids and bases
At pH above the pKa, the solubility of acidic drugs increases. TRUE OR FALSE?
TRUE
At pH below the pKa, the solubility of basic drugs increases. TRUE OR FALSE?
TRUE
How do zwitterions behave?
They behave as acidic at basic pH and bases at acidic pH
Which one of the following is most stable form of paracetamol, Monoclinic or Orthorhombic?
Monoclinic
Orthorhombic undergoes plastic deformation due to a wellodefined planar structure and is suitable for direct compression. TRUE OR FALSE?
TRUE
Are salts forms more water soluble than free acids/bases and more stable?
YES
How can you optimise solubility?
- Salt form - more water soluble than free acid/base and more stable
- Modify pH - so salt form and ionised form predominates and solubility increases
- Co-solvents - Improves solubility for chemicals with poor aqueous solubility, but offer issues with toxicity
What is Cyclodextrin used for?
Used for masking properties of drug
What is Calixarene used for?
Used for masking properties of drugs, however, this is three dimensional. (they rotate and produce different conformations)
Give an examples of aqueous vehicle?
Purified water Bp or USP prepared by distillation, ion exchange or reverse osmosis
Purified water is not to be used for parental formulation ,water is used for injections. TRUE OR FALSE?
TRUE
Give examples of co-solvents?
Glycerol - miscible in water
Alcohol USP
Surfactants
