W11 Routes Of Administration- Oral Flashcards
(36 cards)
What are the different routes of administration?
Oral, Ocular, Nasal, Ear, Inhalation, Intramuscular, Intravenous, Intra-arterial, Topical, Subcutaneous, Vaginal, Rectal, Intrathecal & epidural, Intrathymic, Intracardiac
Sublingual- Under the tongue
Buccal- Inside the cheek
Top 5 prescribed medicines in NHS England primary care in 2019 (in millions)
(for info)
Astorvatin- Cholesterol
Levothyroxine
Omeprazole- Stomach
Amlodipine- Blood pressure
Ramipril
Top 5 administration routes of globally approved
products between 2013–2018 (in %)
Oral, Injection, Opthalmic, Topical, Inhalation
Define Absorption:
Movement of drug from site of administration to the
bloodstream
Biological membranes- Lipid bilayer (for info)
There are different types of phospholipids:
Sphingomyelin
Phosphatidylcholine
Phosphatidylserine
Phosphatidylinositol
Phosphatidylethanolamine
Cholesterol regulates the fluidity
Glycolipid- lipid with carbohydrate chain attached
How thick is the lipid bilayer?
5-8nm thick
What molecules can pass through the cell membrane?
Hydrophobic, small, uncharged molecules (non-ionic)
Water-soluble components
(Na+, K+, and Cl−) of the cell
retain inside the cell
What are examples of transcellular transport?
- Passive diffusion
- Carrier mediated transport
- Facilitated diffusion
- Active transport
- Vesicular transport (endocytosis)
What are examples of paracellular transport?
-Tight junctions
Some hydrophilic molecules pass through this way
Why do epithelial cells in the small intestine have microvilli?
To increase the surface area for absorption
What happens during Gastric emptying? (food)
- How is it regulated?
- Role of chyme?
- Regulated by neural reflex and hormonal mechanisms
- Most vigorous peristalsis and mixing occurs near the pylorus.
- Stomach pressure remains constant until 1L of food ingested
- Relative unchanging pressure results from intrinsic ability of smooth muscle to exhibit “plasticity”
Chyme is either:
- Delivered in small amounts (about 3mL) to the duodenum.
- Forced backward into the stomach for further mixing
What affects gastric emptying?
- Meal volume
* Gastric emptying is a simple exponential
function of the volume of a meal - pH of content
* Acids delays gastric emptying
* pH of chyme in the small intestine of (< 3.5 –4) will activate reflexes to inhibit stomach
emptying until duodenal chyme can be
neutralised by pancreatic and other secretions
* Careful of antacids (e.g. aluminium
hydroxide gel) that raise the pH of stomach
contents - Meal composition
* Stomach empties liquids faster than solids
* Carbohydrate-rich chyme quickly moves through duodenum
* Fat-laden chyme is digested more slowly causing food to remain in the stomach longer
Acidic/basic?
The stomach is….
The small intestine is….
Acidic
Basic
What is the Gastric emptying rate (GER)?
Speed with which substances leave the stomach after ingestion
e.g. rapid emptying with glucose and slow emptying of a viscous meal.
What has greatest capacity for the absorption of drugs from the GI tract?
Where does a swallowed drug go?
What will a delay in gastric emptying mean?
The duodenum.
The stomach then it is emptied into the small intestine.
It will slow the rate and possibly the extent of
drug absorption
Aspirin is taken with what caution (instructions)?
Take with food
* May irritate the gastric mucosa
during prolonged
Amoxicillin/penicillin is taken when?
- Take before food
- Improve absorption as food can affect absorption
- Unstable in acid and will decompose if stomach emptying is delayed
What is the Rate-limiting step?
Slowest step in the series, which controls the
overall rate and extent of appearance of the intact drug in the systemic circulation
Examples of rate-limiting steps in drug? absorption? (5)
- Drug release from dosage form – disintegrate
- Gastric emptying
- Dissolution – high log P hardly dissolves
- Permeability – low log P is hardly absorbed
- Metabolism – including metabolism in the liver (first pass effect)
What is the Dissolution (P) equation:
What do the log P values mean?
P= [Organic solvent] / [Water]
High log P- hardly dissolves
Low log P is hardly absorbed
Features of the Small intestine epithelium (for info)
- Epithelium brush border
- 3000 microvilli per cell
- 200,000,000 per mm
- With this surface area even ionised weak acids will be absorbed in sufficient quantities.
What are the different types of tablets? (6)
- Disintegrating tablets
- Chewable tablets
- Effervescent tablets
- Lozenges
- Sublingual tablets
- Buccal tablets
What are the advantages of tablets? (5)
- Ease of administration and patient acceptance
-Swallowing
-Chewable formulations
-Elegance
-Convenient handling/compactness - Accurate dosage
- Chemical and physical stability
- Different to tamper with
- Low cost of manufacturing, packaging, shipping
Disintegration and dissolution of tablets:
What are the 3 steps?
- Disintegration
- Deaggregation
- Dissolution=Drug in solution
