Colliodal Dispersed Formulations 1 W2 Flashcards
What are dispersed systems
2 phase system in which an insoluble or immiscible dispersed phase Is distributed through a continuous phase
What is amoxicillin
Broad spectrum pencilling type antibiotic
For:
o Severe infections of the ear, nose and throat
o Acute exacerbations of chronic bronchitis
o Community acquired pneumonia
o Lyme disease
o Bacterial meningitis
- It can be delivered as tablets or capsules but also as a liquid, orally or intravenously.
Solubility and dose of amoxicillin
solubility in water is pH-dependent, ranging from 1.7 mg/mL at pH 5.5 to 8.5 mg/mL at pH 7.5.
lowest available dosage form is 125mg/5mL
it rapidly degrades in aqueous solution
How can Amoxicillin be used in a liquid formulation?
Shake powder and mix with water to make a liquid suspension
What is calpol
an OTC paediatric formulation of paracetamol
Paracetamol is very bitter-tasting, and
It’s solubility in water is about 14 mg/mL, less than
the dose required (120 mg/5 mL, i.e. 24 mg/ml
What is gaviscon
is an OTC medicine for acid reflux and indigestion
o Its active ingredients are: sodium alginate and potassium hydrogen carbonate
o The potassium hydrogen carbonate is an antacid,
which neutralises the stomach pH.
o But alginate is the key ingredient
Alginates and rafts
o alginate gels at low pH, so it forms a raft on top of the stomach contents, stopping splashing
back up into the oesophagus.
o To form an effective raft, doses of 250 mg / 10 mL are delivered.
o Alginate’s solubility is pH-dependent (lowest in acidic pH -> gel-forming ability in stomach)
o Maximum solubility of alginate at pH 6-8 is 10 mg/mL
What is a suspension
2 phase dispersed system with a solid dispersed layer and a liquid continuous phase
Particles in pharm suspensions are typically:
0.1 – 10 μm (100 – 10,000 nm)
0.1 – 10 μm (100 – 10,000 nm) is an intermediate state between 2 types of dispersed system:
o Colloidal (for particle sizes less than 1 μm, i.e.
nanoscale)
o Coarse (for particles above 1 μm) This distinction is critical for thermodynamic stability
If a system is thermodynamically stable ….
It will remain in its present state
If a system is thermodynamically unstable ….
It will change in order to reach a stable state
Thermodynamic instability flow chart
Dispersion -> sedimentation -> aggregation
