Routes of Administration I Flashcards
What questions would you ask when developing medicine?
Purpose of API, Which disease and location. best ROA, best dosage form
Describe systemic delivery
Drug delivery to site other than that it’s applied to - Pass through systemic circulation to target organ
Describe local delivery
Drug delivery directly to site of action
Describe disadvantages of systemic delivery
Side effects throughout entire body, exposed to infection
Describe advantages of local delivery
Inc conc at site, side effects only occur at side
What dosage form would you administer drug Terbinafine to treat Athlete’s foot?
Local delivery of an API in topical cream dosage form, if infected also give antibiotics (Alternate: Gel/spray)
What dosage form would you administer Salbutamol to treat an asthma attack?
Local delivery to the lungs via asthma pump to reach alveoli
What dosage form would you administer Mesalazine to treat Crohn’s disease (Colon ulcer)>
Local delivery to colon with oral tablets/capsules dosage form to reduce spread
What dosage form would you administer Sodium Valproate to treat epilepsy?
Systemic delivery via bloodstream with oral tablets (b-blockers) to target optical receptors (Also: IV)
Describe the difference between enteral vs parental delivery?
Enteral - Administration via GI tract
Parenteral - Mainly IV, all other routes eg ocular, nasal, transdermal, pulmonary
In all cases except IV, how do drugs reach bloodstream?
Pass biological barrier (membrane of liver via first pass metabolism) = Causes less drug to enter blood
Describe topical routes
Applied to the surface of the body, can be local or systemic effect eg topical cream vs transdermal patch
Describe mucosal routes
Some topical routes are mucosal routes
Mucosal = Wet surfaces of the body that secrete mucous
Name systemic vs local mucosal treatments
Local - Buccal treatment for mouth ulcer (bonjela)
Systemic - Rectal if babies can’t swallow orally
What 3 factors influence the choice of dosage form?
Scientists/Clinicians - Best opinionated treatment
Patients - Compliance, preference, ease
Manufacturers - Transport, cost
Define onset of action
Speed at which the drug action starts according to the ROA and dosage form
Describe the types of dosage form associated with each time of onset
Seconds - IV Minutes - IM, SC, buccal, aerosol Minutes-hours - Solutions, suspension, powders, capsules, granules Hours - Enteric-coated formulations Days - Depot injections Varies - Topical formulation
Describe why subcutaneous injections only take minutes
Means just under the skin so rapid onset eg for insulin
Describe why powders take minutes-hours
Tablets need to dissolve/break down before absorption
What is an enteric-coated formulations and why does it take hours?
Tablets coated to control when and where it is dissolved/absorbed, specifically to SI via pH response
Briefly describe LADME
Liberation - Drug passage from dosage form
Absorption - Drug uptake to bloodstream across SI
Distribution - Drug moving from abs site to target site
Metabolism - Drug interaction modified
Excretion - Elimination via kidneys (urine/faeces via liver/GIT)
Describe liberation in detail
Removal of drug from tablet to dissolve before it reaches system
Describe metabolism in detail
Body changes drug chemistry (activation) via GI fluid with enzymes
Is a drug absorbed and excreted at the same rate?
No
How do you determine drug systemic availability?
Measuring plasma conc with time
Describe a plasma conc vs time graph
Absorption causes rapid inc in plasma conc until Cmax, slowly declines as elimination occurs (wide bell shape)
What does Cmax show?
The maximal conc of drug abs into the blood, no more drug left to abs
Define bioavailability
Measurement of rate and extent of active drug reaching systemic circulation, available at site of action for an effect
When would the bioavailability be low?
If a systemic drug is metabolised into an inactive form
Briefly define hepatic first pass metabolism (HFPM)
Reduces extent of absorption of drug
Describe how HFPM occurs
Presystemic metabolism (before drug’s in blood)
Abs via gut, enter blood via portal circulation
Transported to liver
Metabolised by liver enzymes (drug now inactive)
Destruction by liver = HFPM
Which dosage forms are affected by HFPM?
Enteral delivery - Oral tablets become inactive if abs by liver
Parenteral - IV don’t enter portal circulation
What happens to drugs in the body?
Pharmacokinetics
Drug absorbed, enter blood, either distributed to tissues/receptor sites, metabolised or excreted
What do barriers within the body cause?
Dec permeation = Dec rate/extent of abs = Dec bioavailability
