pharmacology Flashcards
When do we used sodium valproate?
- epilepsy (anti convulsion)
2. bipolar disorder (acute disorders and prophylaxis): mood stabiliser
What is the mechanism of action of sodium valproate?
- weak inhibitor of neuronal voltage gated NA+: stabilises resting membrane potentials and reduces neuronal excitability
- GABAergic: inhibits GABA transaminase (increases GABA concentration at receptor sites)
What are the side effects of sodium valproate?
nausea, dyspepsia, weight gain, hepatic and renal impairment, dizziness, drowsiness, thrombocytopenia, hair loss
What are the problems with using valproate sodium during pregnancy?
folate antagonist properties: inhibits the DHFR protein (enzyme used to activate folic acid and before it enters folate metabolism cycle)
What is the mechanism of action of lithium?
increase GABA
When do you use Gabapentin?
- epilepsy ( anticonvulsant): usually as an add on treatment if other epileptic drugs provide inadequate control
- Neuropathic pain
- Migraine prophylaxis
- GAD
What is the mechanism of action of gabapentin?
reduction of axon excitability:
acts on voltage sensitive calcium channels (binds to alpha-2 delta subunits): prevents inflow of calcium which inhibits neurotransmitter release (glutamate, noradrenaline and substance P)
What are side effects of gabapentin?
somnolence, dizziness, ataxia, fatigue
When do you use tricyclic antidepressants?
- moderate to severe depression (when first line SSRIs are ineffective)
(2. anxiety) - neuropathic pain
What are the side effects of tricyclic antidepressants?
- antimuscarinic receptors: dry mouth & nose, constipation, urinary retention and blurred vision
- histamine and adrenergic receptors: sedation, hypotension
- arrhythmia,ECG changes
- convulsions, hallucination and mania
DON’T STOP THEM SUDDENLY
What are the mechanism of actions of tricyclic antidepressants?
- inhibits presynaptic 5-HT and NA reuptake transporters: increase synaptic neurotransmitter availability (monoamine theory of depression)
- analgesic mechanism unknown: thought to result from modulation of inhibitory systems and opioid systems in CNS
When do you use lidocaine?
- local anaesthesia
2. ventricular arrhythmias
What is the mechanism of action of lidocaine?
Blockage of fast voltage-gated NA+ channels in neuronal membrane: prevents depolarisation along axon (propagation)
What are the side effects of lidocaine?
- dizziness/drowsiness
- paraesthesia
When do you use paracetamol?
- analgesic effects in acute and chronic pain
- reduce fever: antipyretic effects
What is the mechanism of action of paracetamol?
increases pain threshold in CNS by inhibiting COX (cyclooxyrgenase)
- reduces prostaglandin PGE2 concentration in thermoregulatory region of hypothalamus
- COX 2 inhibition: reduces inflammation (weak anti-inflammatory)
What are the SE of paracetamol?
in overdose: liver failure
When do you use ibuprofen?
- analgesia (mild to moderate pain)
- anti-inflammatory
(3. antipyretic)
What is the mechanism of action of ibuprofen?
-inhibition of COX2: prevents prostaglandin formation from arachidonic acid
(COX2 is expressed in response to inflammatory stimuli–> causes pain)
What are the SE of ibuprofen?
- -> due to COX1 inhibition:
- nausea and dyspepsia
- GI ulceration/bleeding
- risk of hypertension in chronic use
- cardiovascular event
When do you use morphine?
- acute severe pain
- chronic pain
- breathlessness (in end of life care)
- acute pulmonary oedema (breathlessness and anxiety)
What is the MOA of morphine?
Activation of mu receptors (G protein-coupled receptors) in CNS
- -> reduces neuronal excitability (post-synaptic opioid receptor activation causing hyper polarisation) recent and pain transmission (activation of pre-synaptic opioid receptors: reduced intracellular cAMP C°, decreased Ca ion influx and thus inhibits release of excitatory neurotransmitters)
- -> in medulla: blunt response to hypoxia and hypercapnoea (reduces rest drive and breathlessness)
- -> reduces fight or flight activity (by reducing pain, breathlessness and associated anxiety)
(also acts on GABA neurones that modulate dopamine: by inhibition GABA you are able to increase dopamine)
What are the SE of morphine?
- respiratory depression (by reducing respiratory drive)
- euphoria and detachment/ neurological depression
- nausea and vomiting (activa° of chemoreceptors trigger zone)
- pupillary constriction (stimulation of E-W nucleus)
- constipation (increase smooth muscle tone and reduces motility)
- skin itching (histamine release)
- -> tolerance, dependence, withdrawal reaction
What is co-codamol?
codeine and paracetamol
When do you use co-codamol?
mild to moderate pain, as a second line treatment when simple analgesics are insufficient
What is the MOA of co-codamol?
- mechanism of paracetamol
- metabolised by cytochrome P450 enzymes to morphine (or morphine related metabolites)