Flashcards in Drug Delivery Systems Deck (20)
What are the three main factors considered when making up a dosage regime?
o The dose of the drug to be given
o The frequency of administration
o The timing of administration
What is the rate-limiting step in absorption of oral tablets?
Dissolution or tablet break down is the rate limiting step in absorption
What are the advantaged of giving drugs as pills or tablets?
o Accuracy of dose
o Drug stability
o Ease of mass production
What are enteric coated capsules?
Enteric coating delays disintegration of the tablet by gastric acid until it reaches the small intestine
Why are drugs enteric coated?
o Protect the drug from stomach acid
o Protect the stomach from the drug
Why are prolonged release formulations useful?
o Most disorders required prolonged therapy
o Maintains drug levels within a therapeutic range
o Reduces the need for frequent dosing
o Compliance is improved
o Improved nursing and doctor compliance
What are pro-drugs?
Pro-drugs are synthesised inactive derivatives of an active drug which requires to be metabolically activated after administration
What are the advantages of pro-drugs?
o Prolongation of duration of action
o Avoidance of degradation of the drug in the gut
Why are buccal and sublingual drugs useful?
Ideal method for drugs which have extensive pre-systemic or first pass metabolism
When would rectal suppositories, creams and solutions be useful?
Useful in the young or old
Patients unable to swallow
To treat local conditions such as proctitis
To achieve systemic absorption (indomethacin)
Bypass pre-systemic metabolism
Whats the benefit of injection based drug administration?
• 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
What are the three methods of injection based drug administration?
When are drugs given intravenously?
o A rapid onset of action is required
o Careful control of plasma levels is required
o A drug has a short half-life
When are intramuscular injections usually used?
• Allows a more sustained duration of action up to months
• Depot injections of contraceptives and neuroleptics
Never if they have an issue with clotting!
What are the benefits of subcutaneous injection?
Easy to use and bypasses need for venous access
What are the benefits of transdermal delivery?
Bypasses first-pass hepatic inactivation
Easy to use
Good patient compliance
Describe the advantages of drug inhalation
o Drug delivered directly to site of action
o Rapid effect
o Small doses used
o Little systemic absorption
o Reduced adverse effects
What are the disadvantages of drug inhalation?
Patient education is essential
What are liposomes?
Liposomes are self-assembling closed colloidal structures composed of lipid bilayers and have a spherical shape in which an outer lipid bilayer surrounds a central aqueous space. Synthesised from cholesterol and can be used as drug delivery systems