Lecture 5 - Drug formulation Flashcards
factors affecting bioavailability
rate of disintegration of tablet
rate of dissolution of drug particles in intestinal fluid
Physical factors affecting
Pharmaceutical availability (4)
*Tablet compression and excipients
- affect the rate of tablet disintegration
*Other tablet excipients
- affect interaction with aqueous GI juices
*The form of the drug
- e.g. crystalline or salt form (effect of counter ion on
solubility)
*Particle size
Two formulations of a drug with a significant difference in
bioavailability are said to be _______
bioinequivalent
when are 2 similar drugs therapeutically equivalent
if they have comparable efficacy and safacty
give an example where bioinequivalance had serious clinical consequences
phenytoin toxicity 1968
- switch from calcium phosphate to lactose
- rate of bioavailability enhances with lactose formulation
what is rout of administration determined by ?
- Therapeutic objective (slow or fast onset of action)
- Properties of the drug
what differences is control of insulin absorption achieved by ?
- physical state; Crystalline or
non-crystalline - The zinc or protein content
- The nature and pH of the
buffer suspension
describe ultralente insulin
large crystals of insulin and high zinc content
in a solution of sodium
acetate/sodium chloride
Describe Insulin BP
soluble and amorphous
- rapid onset and short duration of action (6h)
what is the onset and duration of action for ultralente insulin
onset 7h
duration 36h
give an example of drugs owking alonside oils to slow down diffusion
e.g.
Vasopressin tannate in oil –
diabetes insipidus
Fluphenazine decanoate in oil -
schizophrenia
Give an example of where plasma drug concentrations differ between IM and Oral
e.g.
phenytoin – plasma
drug concentrations after
IM injection ~ half those
after oral dosing
Chloramphenicol –
also poorly absorbed after
IM injection
describe dibetes insipidus
- lack of ADH (vasopressin)
- leading to excessive water loss in urine, causing dehydration and frequent urination.
what is ADH?
ADH (vasopressin): Adds water pores in the kidney’s collecting duct, allowing water to be reabsorbed into the blood.
what prolongs the effect of local anaesthetic and prevents the drug to be carried away by circulation from site of injection?
formulations containing ADRENALINE
what avoids 1st pass metabolism?
sublingual
buccal
rectal
transdermal
give an example of Avoidance of 1st pass
metabolism
e.g. glyceryl trinitrate so 10 x
less of dose required for
therapeutic effect compared
to oral dosing
______ can be given by
the rectal route for direct effect
on the large bowel
Corticosteroids
give an example of delayed release from coat and why it is used
enteric coated aspirin - release delayed until SMALL INTESTINE
- reduces risk of gastric erosions
what is an example of a drug already having good duration effect so not need to give unconventional formulation?
b-antagonists (porpanonol)
give an example of a drug which has short duration of action
nifedipine - chest pain and hypertension
minimum criteria to be met to produce combination products
- frequency of administration is the same of 2 drugs
- fixed doses in the combination product are therapeutically and optimally effective
give an example of ease of administration for combined drugs
Triple vaccine (diphtheria, tetanus, pertussis)
give an example of improved complience combo drugs
Antituberculous drugs (rifampicin + isoniazid)
Ferrous sulphate + folic acid (pregnancy)
(Rifampicin + Isoniazid (TB treatment) → Patients need both drugs for months, so combining them reduces pill burden and improves adherence.
Ferrous Sulphate + Folic Acid (Pregnancy) → Pregnant women often need both iron and folic acid, so a single pill ensures they get the necessary nutrients without forgetting one.)
