Drug delivery systems Flashcards
What 5 things are to be considered when determining dosage regime?
- Any renal/hepatic failure
- The recommended doses
- Age & weight
- Disease to be treated
- Drugs Toxicity
- starting dose and increased dose needed to achieve the desired effect
Where are oral meds absorbed into systemic circulation?
GI tract
Define a suspension:
Coarse drug particles in a liquid phase
What type of drugs are used in suspension?
Insoluble & unpalatable drugs
What type of patients would use solutoins/suspensions over tablets?
People with swallowing difficulties including the very young & old.
How are solution & suspensions delivered?
By naso-gastric or Peg tubes
What is the rate limitng step in tablet absorption?
The tablets break down or “dissolution”
What are the main advantages of tablet/capsule drugs?
- convenient
- accurate doses
- easily reproduceable in mass
- high drug stability
Why would you use an enteric coating on a tablet?
- to protect it from destructive stomach acid (Allowing it to reach the small intestine)
- to protect the stomach from a toxic drug,
What drugs are enteric coated & why?
Omeprazole, to protect it from stomach acid
Aspirin to protect the stomach from it.
Why don’t enteric coated tablets disintegrate till they reach the small intestine?
They only disintegrate in higher pHs, the stomach is very acidic so theyre unchanged in it.
What are the advantages o prodrugs?
- avoid drug degradation in the gut
- prolongation of duration of action
What does a prolonged release formulation do?
-contains more of the active drug but releases it more slowly over a prolonged period.
How does usin prolonged release formulations improve patient compliance?
Prolonged release formulations need less frequent doses, increasing the odds a patient will take them all
n what 3 forms do prolonged release formulation geerally come?
Oral tablets
Intramuscular Injection
Surgical implants
What drugs are delivered by surgical implant?
Progesterone (contraception)
Testosterone
Why drugs are ideal for buccal/sublingual administration?
Those with a large pre-systemic or first pass metabolism
Do rectally delivered drugs treat locally or systemically?
Rectally delivered drugs can treat both local & systemic conditions
For what type of patient are rectal route drugs useful?
those unable to swallow
In what forms do rectal drugs come?
As creams
Liquids
Suppositories
Do drugs delivered vaginally treat locally or systemically?
Vaginal route drugs treat local disease
In what form are most vaginal route drugs?
Creams
For what type of patient are IV drugs especiall useful?
Unconscious or comatose patients
Why is IV good for drugs with short half-lives?
Allows constant infusion of them so the drug level remains within the therapeutic range.
Are IV drugs rapid or slow release?
rapid systemic effects
For what type of drugs is IV delivery especially useful.
Short half life drugs
And drugs with a narrow therapeutic index.
what type of drus are delivered intramuscularly>
Insoluble drugs or those fomrualted in an oil base
Examples of drugs given by subcutaenous injection?
HEparin
Insulin
Narcotic Analgesics
How long do intramuscular injected drugs work?
Drugs injected intramuscularly can have sustained durations of up to months
You cant see a patients veins but desperately need to deliver fluid what method do you use?
Subcutaneuous injection
In what ways are subcutaneous injections deivered?
- Dermojet (needles)
- Solid pellet implanteed below skin
- Pumps (e.g. insulin pump)
Drug is delivered via an adhesive patch on the skin, what delivery method is this?
Transdermal delivery
How are transdermal drugs absorbed into circulation?
They cross skin by percutaneous absorbtion
What is percutaneous absorbtion?
Absorption of a substance through unbroken skin
Are transdermal drugs used for local or systemic effect?
Transdermal drugs can be systemic or local
Are inhalation drugs used for local or systemic efects?
- Inhalation drugs have local effects.
- Only inhaled anaesthetics are systemic.
Why are inhalation drugs useful?
Drugs are delivered direct to site of action with rapid effect & no first pass metaolism.
Why do inhaled drugs only need small doses?
Only around 5-10% is absorbed systemically so the dose doesnt need to account for absorbtion or metabolism.
Are inhaled drugs more less toxic?
Administering drugs by inhalation actually has a reduced adverse effect
Name 4 carier based systems:
- Monoclonal antibodies
- Liposomal carriers
- Nanoparticles
- Genetic transfer systems
What do monoclonal antibodies do?
- Monoclonal antibodies bind to cancer-specific antigens.
- Then produce induced immunological respones against the cancer
What is a liposomal carrier?
A liposome packed with drugs, transports the trhough the blood
How do liposomal carriers affect the drugs pharmacokinetics?
Drugs carried by liposomes acummulate at disease sites & have reduced distribution at senditive tissue
Whats the main benefit of nanoparticle carriers?
Allow specific targeting/delivery of drugs.
What effect do nanoparticles have on treatment?
The drug has reduced toxicity while maintaining therapeutic efficiency (beacue its targeted)
What type of organisms are used as vectors for genetic transfer?
Viruses
How are viruses altered for genetic tranfer systems?
The virus has the genes for viral replication removed and the therapeutic genes inserted.
What does a genetic transfer system do?
The altered virus delivers the therapeutic gene to target cells.
What do the different drug formulation allow?
A treatment regime to be tailored to a:
- patients needs
- pharmacological characteristics
- disease state
Why are drug delivery systems formulated?
- to allow selective targeting to tissue site
- to avoid pre- or systemic metabolism
- to allow a 24 hour action
what are the 4 ways drugs are deliverd?
-oral
-injection
0transdermal
-carrier based
What are the three factors we used to determine which type of drug delivery system to use?
- dose of the drug to be given
- frequency of admiistration
- timing of administratin
Examples of oral deliver systems?
- solutions and suspensions
- capsules
- tbablets
- modified release tablets
Why are prolonged drugs useful?
- Most disorders require prolonged therapy
- Maintains drug levels within a therapeutic range over a longer period
- reduces the need for frequent dosing
