Non-Oral Absorption Flashcards Preview

Pharmacokinetics and Biopharmaceutics > Non-Oral Absorption > Flashcards

Flashcards in Non-Oral Absorption Deck (12):

What is the purpose of non-oral routes of administration?

  • Many non-oral routes of administration are intended for a local delivery of drug
    • e.g. a cream to treat a fungal infection on the skin
  • However, this is not always the case, and even if it is intended for a localised exposure some systemic absorption may occur


If a systemic effect is required, then the drug must be absorbed into the systemic circulation. Oral administration is the most common route of administration, but it may not be suitable, why not?

  • The drug may have a high first-pass effect, poor stability in gastric fluid (for example), or poor absorption across the GIT wall, and hence low bioavailability
  • The person may not be able to swallow (unconscious, vomiting, very young etc)


What are the advantages and disadvantages of sublingual/buccal routes of administration?

  • Advantages: easy to take, rapid absorption, lipid soluble drugs, avoids first-pass metabolism
  • Disadvantages: limited size of dosage form, limited duration of administration


Describe local administration or system delivery of inhalation

  • Large surface area of the alveoli
  • High permeability of the alveoli epithelium
  • Rich blood supply perfusing the lungs
  • Drug absorbed directly into the system blood stream


What are the advantages and disadvantages of inhalation?

  • Advantages: rapid absorption, onset of action, avoidance of first-pass
  • Disadvantages: poor efficiency of the dosage form (dependent on particle size range), dose size limitation, stimulate cough reflex


Advantages and disadvantages of Rectal/Vaginal?

  • Advantages: good blood supply, partially bypass first-pass
  • Disadvantages: small surface area (less permeable), release of drug from suppositories can be variable, technique of application


Advantages and disadvantages of intranasal?

  • Advantages: bypass GIT so first pass, rapid absorption, loose-knit membranes (compared to GIT) and therefore good for large molecules, rapid absorption
  • Disadvantages: irritation, local side effects, limited volume/amount of drug


What is oxytocin adequately absorbed from the nasal mucosa compared to oral route?

  • Oxytocin is poorly absorbed orally due to a very high molecular weight (well above the 350 limit for good oral absorption) but is adequately absorbed from the nasal mucosa as it is far more permeable


Where are extravascular injections injected into?

Interstitial fluid


What is the absorption mechanism of extravascular injections?

  • Absorption may occur directly into systemic circulation by passive diffusion of drug into blood vessels (mainly capillaries)
    • blood vessel endothelium much more permeable than other cell barriers
    • ionisation, lipophilicity and mw up to 5000Da have little impact
      • makes for attractive routes of administration


Discuss transdermal sites of application

  • Regions with large or many hair follicles (scalp, forehead): more absorption
  • Regions with thickened stratum corneum (foot, palm, forearm): less absorption


Advantages of transdermal route

  • Drug release over an extended period
  • Patches designed to deliver drug at constant rate
  • Can be removed at any time e.g. nitrates for prevention of angina