Formulation and Administration Flashcards
If a different formulation is more appropriate, what must you consider with the current prescription
Can it be
-crushed to aid administration
-discontinued
-temporarily withheld
-switched to alternative in same class
-switched to alternative formulation or route
What types should you not crush or open up
Why?
MR
Capsules
Enteric coatings (EC) => can cause irritation of stomach lining
Reduce therapeutic effect
Increase SE
Parenteral routes
IV
IM
IT
SC
IN
TOP drops, gel, patch
Enteral routes
Enema
Capsule
Coated tablet
Effervescent tablet
MR
PO solution, syrup, suspension
Rectal suppository
Soluble tablet
Tablet
Factors to consider with formulation
Patient
-can they cope with it?
-extremely ill, IV preferable to IM
Age - young children
-small volume liquid, melt formulations
Age - older children
-tablets and capsules
Absorption site
-short bowel or ileus affects bowel absorption
Action site
-eye drops to avoid systemic effects
-Vanc in CDIff PO but IV for systemic use
Excipient contraindications and considerations
Sugar and DM
Allergies (e.g. latex)
Alcohol in babies, young children
Sodium in effervescent tablets - daily dose can exceed recommended daily salt intake
Aspartame - avoid in phenylketonuria
Arachis oil - from peanuts, avoid in nut allergy
Ethylene glycol
Sucrose - diarrhoea in large doses
Lactose - avoid in severe intolerance
Gelatine - hard/soft capsules an issue in vegetarians
Colourants - sensitivity reactions
Factors affecting oral absorption
Enteric coating => absorb in small intestine
-issue in individuals with ileostomy
Modified release => requires long transit time
-issue in individuals with ileostomy
Liquid can be absorbed faster
Weak acidic drugs can precipitate out in acid of stomach (aspirin)
Binding to other electrolytes limits absorption
-Tetracyclines + Ca
-Tetracycline + antacids
-Tetracyclines + Fe
-Quinolones + Fe
Factors affecting IM, rectal, nasal, sublingual, skin absorption
Poor blood flow reduces rate
Well perfused muscle has rapid absorption
Hot bath increases blood flow
Bioavailability
Proportion of medicine that enters systemic circulation
-reduced by absorption, liver metabolism
Half-life
The time taken for the [drug] to fall by half
If it has a short half life, would need to prescribe more frequently
If extremely short, would need to give as continuous infusion
If renal dysfunction, renal excretion would take longer
-may need to adjust dose of interval
Considerations to make when deciding dosing regimen
Concordance - easier if regimen is simpler
Convenience especially is polypharmacy
QoL - having to get up at night
Use of modified release
Crushing => immediate release
However, they contain a greater dose than standard release, likely to experience toxicity
Drug can be
-suspended
-dissolved in oily base
-solid
-patch form
-eye drops
Difference between brands and generic
Different exipients => different amount of absorption
Generic - bioequivalence but not necassarily the same therapeutic equivalence
For MR or narrow therapeutic index, prescribe by brand to avoid fluctuations in treatment
-diltiazem
-antiepileptics
-lithium
-theophylline
-some IS
Unlicense and off-label
-specials
Off-label - found in BNF
-not conditions within marketing authorisation
Unlicense - found in BNF
-medicine produced and licensed in another country and imported
-medicine unlicensed and produced in licensed manufacturing unit in UK
-medicine unlicensed and produced in unlicensed manufacturing facility
Specials - not in BNF
-unlicensed preparation of medicine
-liquid or powder versions of solids for patients with swallowing difficulties
-prescriber takes responsibility for any issues
Crushing or dissolved => makes medicine offlabel
-changes intended properties of medicine
Timing of dose
Avoid adverse effects
-does food affect uptake?
-does it affect sleep and other ADLs
Maximise therapeutic effect
What time would be most convenient for the individual
