Applied Pharmacokinetics: Routes of Administration Flashcards
Name 3 routes of drug administration.
- Oral
- Rectal
- Parenteral
What’s the limiting factor of oral drug administration
Absorption feom GIT
In which clinic setting is oral meds not absorbed?
- Critically ill patients
- Postoperative ileus
Name factors that enhance or impair GI drug absorb
- Acidic drugs are non-ionized and, therefore, well absorbed
- Absorption area stomach small vs intestine
- Enhanced gastric emptying increase absorption vs. delayed GI emptying
- Tablet formulation
What factor affected by tablet Formulation?
Bioavailability
Name types of drug formulations.
- Powder form
- Solid formulation
- Micronization
- Enteric coated tablets
- Sustained-release formulation.
Describe effects of tablet formululation on bioavailability of the active content; Powder- filled gelatine formulation
Fastest and most reliable as the shell desolves rapidly within the stomach
Describe effects of tablet formululation on bioavailability of the active content: Solid formulation
It has to disintegrate
Describe effects of tablet formululation on bioavailability of the active content: Microionization
Particle size is reduced. Therefore, the surface area of the drug is increased, which is exposed to the solvant
Describe effects of tablet formululation on bioavailability of the active content : Enteric coated
• Coat canbe gum/wax/cellulose
• these dissolve in an alkaline environment, i.e., small intestine, therefore abortion is delayed for hours
Example aspirin
Describe effects of tablet formululation on bioavailability of the active content : sustained-release formulation
• Allows release over extended period
•The dosing frequency is reduced
• keeps plasma concentration relatively static
• Contraindicated in drugs with long half lives
What are the characteristics of rectal drug administration
- Absorption incomplete and unpredictable
- Plasma concentration 80-90% that of oral formulation
- Good blood supply but small surface area no Villi in rectum
- Lower rectum Bypasses portal system therefor Avoids presystemic elimination
- Upper rectum frains into portal system
3 Uses of rectal drug administration
- Pediatric
- Unconscious patient with no iv access
- Persistent vomiting
Give examples of drugs given PR by anaesthetist.
Analgesics : PARACETAMOL, NSAIDS, tramadol.
Antipyretics: paracetamol
Antiemetics: cyclizine, procloperazine
Sedatives: ketamin, Diazepam (rarely)
Caution with rectal drug administration
- Informed consent
- Not use in shocked patients poor blood supply.