LA pharmacologu u Flashcards
anlgesia
loss of pain alone
anaesthesia
loss of all forms of sensation
LA
loss of sensation in circumscribed areas of the body by a depression of exciation in nerve endings or inhibition of conduction process in peripheral nerves
use of LA
1) controlling operative pain
2) controlling post operative pain
3) controlling operative haemorrhage
- due to vasocontrictors
4) diagnosis of pain
5) relief of orofacial pain- topical and injection
contents of LA
- aesthetic agent (weak organic bases)
- vasoconstrictor(reduce blood flow)
- vehicle (ringers solution)
- reducing agent (sodium metabisulphite, prevents oxidation of adrenaline)
- fungicide (thymol)
- preservative (most preservative free today due to allergies
anesthetic agent contents/composition
- Aromatic group linked.. (dissolved in lipid around nerves, important as we need it to go across the nerves)
- intermediate chain linked.. (links the two terminals)
- amino terminal (secondary or tertiary amine)
the intermediate chains are either
esters
amides
amide advantages
more stable
autoclaable
rarely antigenic
most commonly used anaesthetic
lidocaine
which molecuels are able to penetrate membrane of nerves and what does this mean
uncharged
- speed of onset is faster when there are more unchanrged molecules
where are low pHs found
places of inflammation or infection
what does the anesthetic drug penetrate
- epineurium
- perineurium
- endoneurium
non spefici action of LA
lipophulic portion of the molecule may cause swelling of the membrane
blocks voltage gated sodium channels
initially increased thresold for excitation then condtion blocks
vasoconstrictor effects
- block sympathetic vasoconstrictors (therefore dilation)
- direct effect on smooth muscle of vessels is variable (cocaine constricts, lidocaine dilates)
detoxification for each type of LA
Esters broken down to - esterases in blood and liver - benzonic acids and alcohol - urine Amides - mainly broken down in liver - oxidised - some conjugated with glucuronic acids - urine
