Drug delivery systems Flashcards
some types of drug delivery
- oral
- injection based
- transdermal
- carrier based
A drug delivery system can be formulated to
- allow selective targeting of a tissue site
- avoid pre- or systemic metabolism
- allow a 24 hour action
What determines the drug delivery system we use
- The dose of the drug to be given
- The frequency of administration
- The timing of administration
- Desired speed of onset
things to consider when giving dose of drug
- age and weight
- impaired renal function?
- impaired hepatic function?
- consider disease
- consider drug toxicity
- starting dose and increasing dose to give desired effect
Oral delivery systems that are commonly used
- suspensions
- capsules
- tablets
- modified release tablets
Absorption of drugs is via the
GI tract. it can be : - Buccal - Sublingual - Oral - Rectal
Solutions and Suspensions are useful for
- young
- elderly
- patients with swallowing difficulties
Solutions and Suspensions may be given via
naso-gastric or PEG tube
solution and suspension drugs and absorption
- Drugs given in this way are absorbed extremely rapidly
- Absorption depends on gastric emptying and is most rapid from the small intestine
Suspensions are dispersions of
coarse drug particles in a liquid phase
- dose can be contained in a small volume
- Good for drugs which are insoluble unpalatable as they are better tolerated
Most commonly used formulation of drugs is
Tablets and Capsules
tablets and capsules rate limiting step
Dissolution or tablet break down is the rate limiting step in absorption
advantages of using capsules and tablets
- convenience
- accuracy of dose
- reproducibility
- drug stability
- ease of mass production
enteric coated tablets differ from normal tablets as
enteric coating delays the degradation of the tablet until it reaches the small intestine
tablets are enteric coated to
- protect drug from stomach acid omeparazole
- protect the stomach from the drug asprin
Prolonged release formulations are useful because
- most disorders require prolonged therapy
- maintains drug levels within therapeutic range
- reduces the need for frequent dosing
- compliance improved
- improved nursing and doctor compliance
prolonged release formulations contain
more active drug but releases more slowly over a prolonged period of time
Oral Preparations have problems with
possible toxicity
Parenteral Preparations example
Intramuscular injections of flupentixol or risperidone
Surgical Implants example
Progesterone contraception
Testosterone
Prodrugs are
synthesised inactive derivatives of an active drug which it requires to be metabolically activated after administration
The advantages of using prodrugs are:
- prolongation of duration of action
- avoidance of degradation of the drug in the gut
Buccal and Sublingual Administration Ideal method for drugs which have
extensive pre-systemic or first pass metabolism
- Sublingual tablets are small and dissolve slowly under the tongue or in the buccal cavity
- Most common example is GTN
Rectal Route involves
Suppositories, Creams and Liquids
Rectal Route is useful for
- the young or old
- Patients unable to swallow
drugs may be administered rectally to
- treat local conditions such as proctitis
- achieve systemic absorption (indomethacin)
- Bypass pre-systemic metabolism
rectal route drugs are administered as
a suppository
Vaginal Route involves
Pessaries
Creams
drugs may be administered through vaginal route for
local disease
injection based drug delivery systems advantages:
- provides fast systemic effects bypassing first-pass metabolism
- Drugs can be administered in unconscious or comatose patients
- Drugs having short half-life can be infused continuously
Drugs are given intravenously when
- rapid onset of action is required
- careful control of plasma levels is required
- a drug has a short half-life
intravenous formulations may be given slowly to
prevent toxic effects
intravenous drugs have continuous fusion to
ensure accurate control of blood levels especially when a drug has a narrow therapeutic index
In intramuscular injections, an injection of the drug is given into
the muscle mass
intramuscular injection drugs may be
insoluble or formulated in an oil base
- this allows a sustained duration of action for up to months
Subcutaneous Injection administration
common route of administration
- easy to use
- bypasses the need for venous access
used for insulin, heparin and narcotic analgesics (pain relief)
Dermojet is a
subcutaneous needle-less injection used for mass inoculation
pellet implantation is when
a drug is implanted under skin as a solid pellet.
- this provides a uniform systemic effect
example of pellet implantation
testesterone
Transdermal Drug delivery system is when
adhesive patches containing drug are applied on skin
- drug crosse skin surface by diffusion by precutaneous absorption and goes into systemic circulation.
advantage of transdermal drug delivery system
bypasses first-pass hepatic inactivation
Percutaneous includes
creams
ointments
skin patches
Drugs can be administered to the skin to
- achieve a local effect i.e steroids
- a systemic effect i.e HRT or nitroglycerin
recently developed skin patches allow
release of drug from reservoir into skin and then systemic circulation
Using skin patches it is possible to obtain controlled, sustained blood levels of the administered drug such as
- nicotine
- nitroglycerin
- opiates
- HRT (hormone replacement therapy)
- contraception
Transderm-SCOP (Scoplamine) is used for
motion sickness
Hydrogel transdermal patch:
Used in treatment of burns
Inhalation is used commonly to deliver drugs
- directly to the lung for local effect
- to achieve a systemic effect I.e anaesthetics
Advantages of inhalation of drugs
- Drug delivered directly to site of action
- Rapid effect
- Small doses used
- Little systemic absorption
- Reduced adverse effects
disadvantages of inhalation of drugs
patient education is essential
pharmaceutical carriers include
- micelles
- vesicles
- liquid crystals
- nanocapsules
- nanospheres
- multifunctional dendritic polymers
Monoclonal antibodies act directly when
binding to a cancer specific antigen and induce immunological response to cancer cells.
- have been modified for delivery of a toxin, cytokine or other active drug
Monoclonal antibodies have
monovalentaffinity, in that they bind to the sameepitope.
Pre-clinical and clinical liposomal packed drugs exhibit
reduced toxicities with enhanced efficiency
Using nanotechnology the drug can be
targeted to a precise location which would make the drug much more effective & reduce the chances of possible side-effects
nanotechnology advantages
- More specific drug targeting & delivery
- Reduction in toxicity while maintaining therapeutic efficiency
- Nanocarriers- Nanoparticles,Nanotubule,Nanoshell
carbon nanotubules are used in
treatment of Bronchial asthma
gold nonoparticles are used in
cancer chemotherapy.
- free radical generation
nanoerythrosomes are
resealed erythrocytes that can carry proteins, enzymes and macromolecules.
nanoerythrosomes are used for treatment of
- liver tumour
- parasitic disease
- enzyme disease
dendimers are
highly branched globular biodegradable synthetic molecule
modified buckyballs deliver
radioactivity to tumours.
eg- C60 against CA colon
- transfer of radiation is within ball hence minimises strong radiation to healthy tissue
