Oral Administration Flashcards
Top 5 prescribed medicines in NHS England primary care in 2019 (in millions)
1) Atorvastatin
2) Levothyroxine
3) Omeprazole
4) Amlodipine
5) Ramipril
Define absorption …
Movement of drug from site of administration to the bloodstream
Describe the process of gastric emptying (food) …
- Pyloric valances are closed - Stomach pressure remains constant until ~1 L of food ingested
Relative unchanging pressure results from intrinsic ability of smooth muscle to exhibit “plasticity” - the most vigorous peristalsis and mixing occurs near the pylorus
- the pyloric valve then slightly opens and allows chyme to be either Delivered in small amounts (about 3 mL) to the duodenum
Forced backward into the stomach for further mixing
What affects gastric emptying ?
1) Meal volume - Gastric emptying is a simple exponential function of the volume of a meal
2) 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
3) pH of content - acids delay gastric emptying
Define gastric emptying rate (GER) …
Gastric emptying rate (GER) = Speed with which substances leave the stomach after ingestion
What will a delay in gastric emptying cause ?
Delay in the gastric emptying time will slow the rate and possibly the extent of drug absorption
Is aspirin taken before, after or with food ?
Taken with food - may irritate the gastric mucosa during prolonged intake
Is amoxicillin taken before,after of with food ?
Taken before food - improves the absorption as food can affect the absorption
- is unstable in acid and will decompose if stomach emptying is delayed
What is the rate limiting step in gastric emptying ?
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
How does rate limiting step differ from drug to drug ?
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 are the 6 types of tablet ?
- disintegrating tablets
- chewable tablets
- effervescent tablets
- buccal tablets
- sublingual tablets
- lozenges
What are the advantages of tablets ?
- ease of administration and patient acceptance (swallowing, elegance, convenience, chewable formulations)
- accurate dosage
- chemical and physical stability
- difficult to tamper with
- low cost of manufacturing, packaging and stability
What are the two capsule types ?
- hard capsules ( gelatin, alternative polymers)
- soft capsules (gelatin, veggie option)
What are advantages of capsules ?
Patient compliance :
-Easier to swallow
-Smooth & slippery
-Tasteless and odourless
-Eliminate all contact between drug and mouth)
-Can be opened up
-Contents sprinkled on food
-Clear, high-gloss coloured film
-Can be printed on
Drug delivery:
- Fast acting
- Breakdown of capsule shell occurs readily ≈ disintegration of tablet
-Beads/pellets/granules in addition to dry powder fills
-A mixture of beads with different release rates
Other dosage forms in a capsule
Mini tablets and liquids
Which oral dosage form has the greatest bioavailability ?
Liquid oral dosage form (solution)
