Gastric emptying rate (GER) = Speed with which substances leave the stomach after ingestion

Routes of Administration: Oral Flashcards by Alexia✿ !

What is absorption?

Movement of drug from site of administration to the
bloodstream

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What types of lipids are in biological membranes?

Sphingomyelin
Phosphatidylcholine
Phosphatidylserine
Phosphatidylinositol
Phosphatidylethanolamine

Glycolipid – lipid with a carbohydrate attached
Cholesterol – a type of lipid

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What are the two types of cellular transport across membranes?

*transcellular
*paracellular

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What are the types of transcellular transport?

Passive diffusion
Carrier mediated transport
Facilitated diffusion
Active transport
Vesicular transport (endocytosis)

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What is the type of paracellular transport?

Tight junctions

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What structures are involved in the GI tract?

*small intestine
*vilus
*epithelial cells with microvilli

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Describe pressure changes during gastric emptying of food

Stomach pressure remains constant until ~1 L of food ingested
Relative unchanging pressure results from intrinsic ability of
smooth muscle to exhibit “plasticity”

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Describe what happens to chyme (stomach acid) during gastric emptying

Chyme is either:
* Delivered in small amounts (about
3 mL) to the duodenum
* Forced backward into the stomach
for further mixing

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What is gastric emptying regulated by?

*neural reflex
* hormonal mechanisms

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What is gastric emptying affected by?

*meal volume
*meal composition
*pH content

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How does meal composition affect gastric emptying?

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

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How does pH content affect gastric emptying?

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

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What is GER?

Gastric emptying rate (GER) = Speed with which substances leave the
stomach after ingestion

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How do the structures of the GI tract do drug gastric emptying?

The duodenum has the greatest capacity for the absorption of drugs from the GI tract
Anatomically, a swallowed drug rapidly reaches the stomach
Eventually, the stomach empties its contents into the small intestine
Delay in the gastric emptying time will slow the rate and possibly the extent of drug absorption

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What type of advice can be given for oral drugs and the disadvantages?

Take with food
May irritate the gastric mucosa
during prolonged
Take before food
Improve absorption as food can
affect absorption

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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

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What are the various rate limiting steps for different drugs?

Rate-limiting step differs 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 is the SA of the small intestine epithelium?

Epithelium brush border
3000 microvilli per cell
200,000,000 per mm2

How will the epithelium brush SA help?

With this surface area
even ionised weak acids
will be absorbed in
sufficient quantities

What are the different types of tablets? 6 types + example

*disintegrating tablet (Zantac)
*lozeneges (strepsils)
*chewable tablets (gaviscon)
*effervescent tablets (beroca)
*sublingual tablets (nicorette)
*buccal tablets (buccastem m)

What are the advantages of tablets?

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

What are the types of capsules?

*hard capsules
*soft capsules

What are hard capsules composed of?

Gelatin
(bovine, porcine, fish)
Alternative polymers
(HPMC
hydroxypropylmethylcellulose,
pullulan)

What are soft capsules composed of?

Gelatin
Vegetarian option (Vegecaps)

What are the advantages to capsules? in terms of patient compliance

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

What are the advantages capsules? in terms of 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

Describe dissolution of capsules containing both hydrophobic and hydrophilic drug particles

*Hard gelatin capsules containing hydrophobic drug particles and hydrophilic diluent particles * the capsules will dissolve in GI liquid leaving a porous mass of drug *GI fluids can penetrate porous mass *Effective surface area of drug and hence dissolution rate is increased

Describe dissolution of capsules containing only hydrophobic drug particles

*hard capsule containing only hydrophobic drug particles *the capsule shell will dissolve in GI fluid exposing contents *Contents remain as capsule-shaped plug.Hydrophobic nature of contents impedes penetration of GI fluids *Dissolution of drug occurs only from surface of plug-shaped mass. Relatively low rate of dissolution

Why are oral solutions give+ absorption?

* Drugs are commonly given in solution * in cough/cold remedies * for the young and elderly * Absorption from an oral solution is often rapid and complete, greater bioavailability compared to other oral dosage forms

What is the absorption of oral suspensions like?

* Second to a solution in terms of superior bioavailability * Absorption may well be dissolution-limited * Suspension of a finely divided powder will maximize the potential for rapid dissolution

What are sublingual tablets for?

* Sublingual – application to the membranes of either the floor of the mouth or the underside of the tongue and entry into systemic circulation following absorption

What are buccal tablets for?

* Buccal – application to the lining of the cheek – entry into the systemic circulation following absorption

What makes up the Floor of the mouth, the soft palate, the lips and the cheek?

Non-keratinised mucosa

What makes up Hard palate, gingiva and tongue?

Keratinised mucosa

What is the epithelium thickness of the sublingual route?

100 – 200 µm on the underside of the tongue and on the floor of the mouth

What is the epithelium thickness of the buccal route?

500 – 800 µm in the buccal cavity

What are some properties of the sublingual route?

* Relatively permeable * Rapid absorption * Unsuitable for retentive system * Ideal for rapid onset of action * Sprays or fast-dissolving tablets

What are some properties of the buccal route?

* Relatively less permeable * Not rapid absorption * Suitable for retentive system * Ideal for sustained release * Adhesive tablets or patches

What are the three sublingual oral types?

*chewable tablets *sprays *tablet

What are each sublingual oral route made of?

* Sublingual tablets * Consist of lactose mannitol sucrose for fast dissolution * Solutions and sprays * Administration of nitroglycerin (angina prevention) * Chewing gum * A gum base of a cellulosic or acrylic polymer

What are some examples of buccal adhesive tablets?

* Buccastem M: prochlorperazine (antiemetic) * Suscard Buccal: Glyceryl trinitrate (relieves chest pain) * Buccal sustained release of flurbiprofen (NSAID)