Pharmacokinetics- Administration and Absorption Flashcards
How are drugs administered?
Enteral formulations, parenteral formulations, topical formulations
Give examples of enteral formulations
- Tablet
- Capsule
- Liquid
- Suppository
Describe a tablet
- Compressed, contains 5-10% active ingredient
- > 90% fillers (binders, lubricants, disaggregants)
- Aqueous solubility is dependent on particle size and crystal form
- Has enteric coating which prevents disintegration until passage through stomach into intestine
- Sustained/extended/modified release of drug
- Osmotic core, permeable coating allows slow release of drug
What is the effect of extended release drug formulation?
Reduces the frequency of dosing
Describe a capsule
- Gelatinous envelope
- Controllable disintegration speed
- Slow and fast dissolving particles
Describe a liquid/syrup formulation (enteral)
- Possibly faster absorption
- Sugar/sugar-free
- Often paediatric
Describe a suppository formulation
- Rectal
- Torpedo shape
- Used for vomiting patients
Give examples of parenteral formulations
Liquid, Lyophilised
Describe a liquid formulation (parenteral)
- Vials, ampoules, cartridges, pre-filled syringes
- May need diluting (e.g. IV bag)
What does parenteral mean?
Not by gut, i.e. injectable
Describe a lyophilised formulation
- Freeze-dried
- Produces dry powder
- Needs reconstituting with liquid
- Vials, ampoules, dual chamber syringes, etc.
What are topical formulations?
Local action- on the surface
What are enteral formulations?
By the gut
Give examples of topical formulations
- Cutaneous
- Inhaled
Describe cutaneous formulations
- Cream- mixture of oil/water to penetrate skin
- Ointment- oilier, reduces water loss
- Gel-liquefies on contact with skin
- Paste-powder suspended in a cream
Described inhaled formulations
- For lower airways
- MDI- metred dose inhaler
- Breath actuated device
- Nebulisers
Give examples of other administration methods
- Eye drops
- Nasal sprays
- Vaginal, urethral suppositories
What are the different routes of absorption?
- Oral
- Parenteral
- Topical
Describe oral absorption
gastric
- Greatest absorption in the small intestine, not in stomach
- Gastric phase delays drug absorption in intestine
- Drug absorption may be affected by GI contents
What slows down gastric emptying?
- Solid meal (distension)
- High fat meal
High protein meal - Low gastric meal
- Low gastric pH
Describe oral absorption (hepatic portal circulation)
Some oral drugs undergo variable degrees of metabolism in stomach, gut and liver before reaching systemic circulation (1st pass metabolism)
Give a summary of oral absorption
- Convenient but delay in drug onset
- Drug exposed to gastric acid and bacterial and digestive enzymes
- Portal vein –> liver before reaching site of action
- Some drugs undergo significant 1st pass metabolism, adjusted doses may be required
- Enteral routes that avoid 1st pass metabolism include buccal, sublingual and rectal
What does parenteral absorption involve?
- Avoids GI tract and first pass metabolism
- Used against pain, local trauma and infection
- Requires injection
- Trained healthcare staff required
Give examples of parenteral absorption
- Intravenous
- Intramuscular
- Subcutaneous
