Drug Delivery Systems Flashcards
Name the type of drug delivery systems available
Oral
Injection based
Transdermal
Carrier based
In what forms/formulations can drugs be given to patients (7)
Tablets or capsules Solutions or suspensions Ointments and creams Inhalation Injections Suppositories Pessaries
What types of tablets/capsules are there
Regular
Modified release
Prodrugs
Enteric coated
How can a drug delivery system be formulated
To allow selective targeting of a tissue site
To avoid pre- or systemic metabolism
To allow a 24 hour action
What do drug formulations allow
A treatment regime to be tailored to a patients needs, pharmacological characteristics and disease state
What determines the drug delivery system used
The dose of the drug to be given
The frequency of administration
The timing of administration
What should be considered when choosing a dosage regime (7)
Find out the recommended dose (BNF/BNFc) Is there impaired renal function Is there impaired hepatic function Age and weight Disease to be treated Drug toxicity Give a starting dose and increase dose to achieve the desired effect
What are commonly used oral delivery systems (5)
Solutions Suspensions Capsules Tablets Modified release tablets
Where is absorption through using oral delivery systems
GI tract
When are solutions and suspensions a useful form of administration
In the young, elderly and patients with swallowing difficulties
How can solutions and suspensions be given
Through a nasogastric tube or PEG tube
What is the rate of absorption for drugs administered through a nasogastric tube or PEG tube
Extremely rapidly
What is absorption dependent on
Gastric emptying and is most rapid from the small intestine
Describe suspensions
Dispersions of coarse drug particles in a liquid phase
The dose can be contained in a small volume
What are suspensions good for
Drugs which are insoluble unpalatable as they are better tolerated
What limits the rate limiting step in the absorption of tablets
Dissolution or tablet break down
What are the advantages of tablets and capsules
Convenience Accuracy of dose Reproducibility Drug stability Ease of mass production
What does the enteric coating of tablets do
It delays disintegration of the tablet until it reaches the small intestine
Why are some tablets enteric coated
Protect the drug from stomach acid (e.g. Omeprazole)
Protect the stomach from the drug (e.g. Aspirin)
Why are prolonged release formulations useful
Most disorders required prolonged therapy
Maintains drug levels within a therapeutic range
Reduces the need for frequent dosing
Compliance is improved
Improved nursing and doctor compliance
How can the time course for a drug in the body be prolonged
By giving the drug in a form that has a slower but sustained rate of release
This type of preparation contains more of the active drug but releases it more slowly over a prolonged period
Name some oral preparations
Verapamil Diltiazem Isosorbide mononitrate Lithium Carbamazepine
Name some parenteral perparations
Intramuscular injections of flupentixol or risperidone
Name some surgical implants
Progesterone contraception
Testosterone
What are prodrugs
Synthesised inactive derivatives of an active drug which requires to be metabolically activated after administration
What are the advantages of prodrugs
Prolongation of duration of action
Avoidance of degradation of the drug in the gut
When are buccal and sublingual administration ideal
For drugs which have extensive pre-systemic or first pass metabolism
What are sublingual tablets
Small and dissolve slowly under the tongue or in the buccal cavity (e.g. GTN)
What can be administered through the rectal route
Suppositories, Creams and Liquids
When is the rectal route useful
In the young or old
Patients unable to swallow
Why may drugs be administered rectally
To treat local conditions such as proctitis
To achieve systemic absorption (indomethacin)
How is the rectal drugs administered
As a suppository
What is a benefit of the rectal route
Bypass pre-systemic metabolism
What can be used through the vaginal route
Pessaries
Creams
What do drugs administered through the vaginal route treat
Local disease
What are the benefits of injection based drug delivery systems
Provide 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
Name the three different methods of injection based drug delivery systems
Intradermal (10-15 degree angle)
Subcutaneous (45 degree angle)
Intramuscular (90 degree angle)
When are drugs given intravenously
When:
A rapid onset of action is required
Careful control of plasma levels is required
A drug has a short half-life
How can IV formulations be given
Rapidly
Slowly to prevent toxic effects
Continuous infusion to ensure accurate control of blood levels especially when a drug has a narrow therapeutic index
What is an intramuscular injection
An injection of the drug given into the muscle mass
They allow a more sustained duration of action up to months
What type of drugs can be given intramuscularlly
Drugs insoluble or formulated in an oil base
Give examples of intramuscular drugs
Depot injections contraceptive
Neuroleptics
What is a disadvantage of the intramuscular injection
May be painful
Describe the subcutaneous injection
A common route of administration
Easy to use and bypasses need for venous access
Give examples of subcutaneous injections
Insulin
Heparin
Narcotic analgesics
What is dermojet
It is a sub-cutaneous needleless injection used for mass inoculation
What is a pellet implantation
Drug as a solid pellet is implanted under the skin to provide uniform systemic effect (e.g. testosterone)
What us a transdermal drug delivery system
Adhesive patches containing the drug are applied on the skin
How do drugs cross the skin surface in the transdermal drug delivery system
By diffusion by percutaneous absorption and goes into systemic circulation
What does the transdermal drug delivery system bypass
First-pass hepatic inactivation
What types of drug delivery systems have percutaneous administration
Creams
Ointments
Skin patches
What is percutaneous administration
Drugs that can be administered to the skin to achieve a local effect (e.g. steroids) or a systemic effect (e.g. HRT or nitroglycerin)
Describe skin patches
They allow the release of a drug from a reservoir into the skin and then into the systemic circulation
Using skin patches it is possible to obtain controlled, sustained blood levels of the administered drug
Give examples of skin patches
Nicotine Nitroglycerin Opiates HRT Contraception
What is the hydrogel transdermal patch used for
In the treatment of burns
What is the scoplamine (SCOP) patch used for
Motion sickness
What are inhalation drugs commonly used to deliver
Drugs directly to the lung for local effect or to achieve a systemic effect (e.g. anaesthetics)
How is inhalation medication administered
Pressurised aerosol
Breath actuated aerosol
Nebuliser
Dry powder device
What are the advantages of inhalation
Drug delivered directly to site of action Rapid effect Small doses used Little systemic absorption Reduced adverse effects
What is a disadvantage of inhalation
Patient education is essential
How can drug delivery systems be developed in the future
Drugs will be designed according to individual genotypes, so enhancing safety and efficacy
Name the carriers in carrier based drug delivery systems (6)
Vesicles Micelles Liquid crystals Nanocapsules Nanospheres Multifunctional dendritic polymers
How do monoclonal antibodies act in regards to cancer
Act directly when binding to a cancer specific antigen and induce immunological response to cancer cells
How have monoclonal antibodies been modified
For delivery of a toxin, cytokine or other active drug
What do pre-clinical and clinical liposomal packed drugs show
Reduced toxicities with enhanced efficiency
What do altered pharmokinetics do to liposomal drug delivery
Drug accumulation at disease sites and reduced distribution to sensitive tissue (target delivery of drugs)
What is nanoparticle based drug delivery
Drugs targeted to a precise location which would make the drug much more effective & reduce the chances of possible side-effects
What are the benefits of nanoparticle based drug delivery
More specific drug targeting & delivery
Reduction in toxicity while maintaining therapeutic efficiency
Name 3 nanocarriers
Nanoparticles
Nanotubule
Nanoshell
When are carbon nanotubules used
Treatment of Bronchial asthma
When are gold nanoparticles used
Cancer chemotherapy (free radical generation)
What are nanoerythrosomes
Erythrocytes that can carry proteins, enzymes & macromolecules
When are nanoerythrosomes used
Treatment of liver tumours, parasitic disease
& enzyme disease
What is the genetic transfer system
When the natural virus has the genes for viral replication removed and therapeutic genes inserted
This forms a virus carrying the therapeutic gene which infects and delivers the therapeutic gene to target cells
What could the genetic transfer system potentially be used for
Adenovirus
HIV
What is a dendrimer
A highly branched globular biodegradable synthetic molecule
Describe the modified buckyball
They deliver radioactivity to the tumour (e.g. C-60 against CA colon)
The transfer of radiation is within the ball hence it minimises strong radiation to healthy tissue
