Drug Delivery Flashcards
How can drug formulation affect the effect of the drug?
Allow selective targeting of a tissue site or to avoid pre- or systemic metabolism, or to allow a 24 hour action
Treatment regime also needs to be tailored to a patients needs
What determines the drug delivery system we use?
The dose of the drug to be given
The frequency of administration
The timing of administration
What factors do we consider to determine the dose?
Renal function
Hepatic function
Consider age and weight
Consider disease to be treated
Consider drug toxicity
Give a starting dose and increase dose to achieve the desired effect
Where does absorption take place?
Buccal Mucosa
Sublingual
Oral
Rectal
What determines the speed of absorption of solutions and suspensions?
Gastric emptying - most rapid from the small intestine
What is the benefit of Solutions and Suspensions?
Useful way to administer drugs to the young, elderly and patients with swallowing difficulties
Drugs given in this way are absorbed extremely rapidly
May be given via a naso-gastric or PEG tube
What is a suspension?
Dispersions of coarse drug particles in a liquid phase
What are suspensions useful for?
Drugs which are insoluble unpalatable as they are better tolerated
What is the most commonly used formulation?
Tablets and capsules
What is the rate limiting step for capsules and tablets?
Tablet breakdown (dissolution)
What are the advantages of the tablets and capsules?
Convenience
Accuracy of dose
Reproducibility
Drug stability
Ease of mass production
What is the effect of the enteric coated tablets?
Enteric coating delays disintegration of the tablet until it reaches the small intestine
Protect the drug from stomach acid Omeprazole
Protect the stomach from the drug (ulceration)
Aspirin
What is the benefit of Prolonged or Delayed Release Formulations?
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
This type of preparation contains more of the active drug but releases it more slowly over a prolonged period
What are the advantages of prodrugs?
Prolongation of duration of action
Avoidance of degradation of the drug in the gut
What is a prodrug reliant on?
Liver function - metabolism activates the drug
What is Buccal and Sublingual Administration ideal for?
Ideal method for drugs which have extensive pre-systemic or first pass metabolism
How would you take sub-lingual drugs?
Sublingual tablets are small and dissolve slowly under the tongue or in the buccal cavity
What is the rectal route useful for?
Useful in the young or old
Patients who are unable to swallow
Why would you choose a rectal route?
Treat local conditions
Can achieve systemic absorption
Bypasses pre-systemic metabolism
What is the vaginal route used for?
Local disease
What are the advantages of injection based drug delivery?
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
When is intravenous administration used?
When: A rapid onset of action is required careful control of Plasma levels is required
A drug has a short half-life
How may 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
Describe what an Intramuscular Injection is?
An injection of the drug is given into the muscle mass
Describe the type of solution given in intramuscular injection
The drug may insoluble or formulated in an oil base
What is the benefit of intramuscular injection?
Allows a more sustained duration of action up to months BUT May be painful
What are the advantages of subcutaneous injection?
Easy to use and bypasses need for venous access
How does transdermal drug delivery enter the systemic circulation?
Adhesive patches containing the drug are applied on the skin
The drug crosses the skin surface by diffusion by percutaneous absorption
What does transdermal drug delivery avoid?
Bypasses first-pass hepatic inactivation
What is percutaneous drug administration?
Creams, Ointments and Skin patches
Drugs can be administered to the skin to achieve a local effect i.e steroids or
a systemic effect i.e HRT or nitroglycerin
What is the benefit of skin patches?
Possible to obtain controlled, sustained blood levels of the administered drug such as nicotine, nitroglycerin, opiates, HRT, contraception
When are drugs administered by inhalation?
When there is a need to deliver drugs directly to the lung for local effect or to achieve a systemic effect I.e anaesthetics
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 are the disadvantages of inhalation?
Patient education is essential
How do monoclonal antibodies act?
Bind to cancer specific antigen and induce an immunological response to cancer cells
What can Monoclonal antibodies be used to deliver?
Toxin, cytokine or other active drug§
What is the purpose of liposomal drug delivery?
Altered pharmacokinetics results in reduced toxicity with enhanced efficiency
There is reduced distribution of drug to sensitive tissue
What is another method of increasing the precision in targeting of a drug as well as reducing the toxicity?
Nanoparticle based drug delivery - makes the drug more effective and reduces the chances of possible side-effects
What are nano erythrosomes and what are their applications?
Erythrocytes that can carry, proteins, enzymes and macromolecules
Used in the treatment of liver tumour, parasitic disease and enzyme disease
What is the vector for the genetic transfer system involving the delivery of therapeutic genes to target cells?
Viruses
