Lecture 4 Drug Absorption 2 Flashcards
what is the fastes and most certain rout IV?
single bolus injection
- right heart and lungs then the sysemic circulation
what avoids high peak plasma concentrations ?
steady IV infusion
describe difference between subcutaneous and intramuscular injections injection site and absorption rate
injection site subcutaneous - fat layer slower absorption rate
injection site intramuscular - deep into muscle - faster absorption rate
what does rate of absorption therefore depend on?
- site of injection
- local blood flow
- drug formulation
describe the action of an intrathecal injection
injection into subarachnoid space via a lumbar puncture needle
what is subarachnoid space
fluid-filled spaces between the arachnoid mater and pia mater of the brain and spinal cord
give example of intrathecal injection
Methotrexate for treatment of childhood leukaemias
(avoids central nervous system relapse)
Local anaesthetics (e.g. bupivacaine)
Opiate analgesics
Baclofen (a GABA analogue) – for treatment of muscle
spasm caused by chronic neurological disease (e.g. MS)
Some antibiotics (aminoglycosides)
- treatment of nervous system infections with bacteria
resistant to other antibiotics
+ves of inhalation drugs
- rapid action
- minimise systemic absorption
- minimise side effects (beta agonists, glucocorticoids)
3 characterisics of astma ?
- inflammation
- mucus production
- bronchpspasm
what is a key marker of
uncontrolled asthma?
Waking at night with asthma symptoms
describe treatment of symptoms of asthma
adrenergic agonist beta
e.g. pirbuterol
- Relax airway smooth muscle directly
- Rapid onset of action (15-30 min)
- Provide relief for 4-6 hours
- Little stimulation of α or β1 receptors
what are the drugs of first choice in moderate to severe asthma ?
Glucocorticoids
-ve of glucocorticoids
not direct effect on airways smooth muscle
+ve of glucocorticoids
Decrease the number and activity of cells
involved in airway inflammation
(macrophages, eosinophils, T-lymphocytes)
Inhaled drugs: A large fraction -____-___% deposited in the mouth and pharynx
or swallowed. Only ___% depositied in lung.
80-90
10
90% of inhaled drugs undergo extensive first pass metabolism …
A small amount reaches the systemic circulation, which
minimises adverse effects
reason for use of spacers for inhaled drugs
Large particles of aerosol are
deposited in chamber before
patient inhales
Inhaled aerosol is enriched
in small particles which more
readily travel to small airways
Spacer
+ves of other inhaled drugs for asthma i.e.”Sodium cromoglycate and nedocromil sodium”
Effective prophylactic anti-inflammatory
agents (especially histamine)
-ves of other inhaled drugs for asthma i.e.”Sodium cromoglycate and nedocromil sodium”
not useful in managing acute attacks of
asthma – not direct bronchodilators
examples of delivery devices for inhaled medications
- pressurized metered dose inhaler
- dry power inhaler
- nebulizer
Describe action of theophylline
-POTENT bronchodilator
- But narrow therapeutic window
- overdose– seizures, cariac arrhythmias - bas drug drug interactions
give an approach and example for the issue of current inhalers wearing off quickly (4-6 hrs)
Prolonged release inhalation formulations: LIPOSOME ENCAPULATION (Tiny fat-based carriers slow drug release.)
e.g
Cytosine arabinoside → Lung cancer treatment 🎯
Sodium cromoglycate → Asthma prevention
