Physiology and pharmacology 2 Flashcards
why is vasoconstrictors used?
- increase speed of onset
- counteract vasodilatory effects of the LA agent
- extend duration of anaesthesia
- improve depth of anaesthesia
- lower blood levels of LA
- reduce haemorrhage
Name the 2 types of vasoconstrictors.
-Sympathomimetic amines: adrenaline (epinephrine)
-Synthetic polypeptides:
Felypressin (octapressinTM)
Describe the features of adrenaline.
- alpha 1 receptors - vasoconstriction
- Usually 1:80,000 = 12.5μg/ml
- 2.2ml cartridge = 27.5 μg
- Requires a preservative to maintain shelf life
what are the systemic effects of adrenaline?
– direct: raises rate and force of contraction -> cardiac output
– may increase blood pressure
– vasoconstrictive (adrenaline more so than Felypressin)
Describe the features of felypressin.
- 0.03 IU/ml = 0.54μg/ml
- analogous to vasopressin
- works on venous side (as oppose to adrenaline thats works at arterial end)
- vasoconstrictive potency is about half that of adrenaline
- poor haemostasis compared to adrenaline
why is felypressin avoided in pregnancy?
-Mild oxytocic effect
- theoretical risk of interfering with placental
circulation and uterine tone
-however dose used in dentistry is small:
– Need ~ 100 cartridges to induce labour (Meechan 2002)
-despite low risk, should AVOID in pregnancy
what are maximum recommended doses for a healthy adult?
– Lidocaine 2% + Adrenaline 1:80,000
• Absolute maximum = 500mg
– Lidocaine 2% plain
• Absolute maximum = 300mg
why is there a higher maximum dose when a vasoconstrictor is used?
Slows down systemic uptake of drug
what maximum dosage is used?
lower maximum dosage (300mg) is used because vasoconstrictor effect can be variable
what is the maximum anaesthetic in lidocaine?
-lidocaine hydrochloride
2% = 20mg/ml (=44mg in a 2.2ml cartridge)
what is the maximum vasoconstrictor (adrenline) in lidocaine adrenaline?
1:80 000 = 12.5microgram/ml
what is the preservative in lidocaine and adrenaline?
sodium or potassium metabisulphite
what is the maximum anaesthetic dose of lidocaine and adrenline?
4.4mg/kg (up to a max of 300mg*)
how many cartridges are used in dentistry for LA?
very rarely require more than 3 (maximum is 6.8 cartridges)
what is the maximum dosage of anaesthetic in mepivacaine (scandonest 3% plain)?
– Mepivacaine Hydrochloride
– 3% = 30mg/ml (= 66mg in a 2.2ml cartridge)
what is the maximum vasoconstrictor in mepivacaine?
none - because least vasodilatory so reasonable duration when used plain
what preservative is used in mepivacaine?
none
what is the maximum anaesthetic dose of mepivacaine?
4.4mg/kg (absolute max 300mg)
what is maximum dosage of anaesthetic in prilocaine and felypressin (citanest 3% with octapressin)?
– Prilocaine Hydrochloride
– 3% = 30mg/ml (= 66mg in a 2.2ml cartridge)
what is the maximum vasoconstrictor in prilocaine and felypressin?
– Felypressin (Octapressin)
– 0.03 IU/ml = 0.54μg/ml
what is the preservative in prilocaine and felypressin?
not required
what is the maximum anaesthetic dose of prilocaine and felypressin?
6mg/Kg (absolute max 400mg)
what is used for most injections?
lidocaine/adrenaline
when is lidocaine/adrenaline not used?
if patient has:
– Unstable angina
– Severe Cardiac dysrhythmia
– Allergy to any components
Caution with other cardiac conditions – avoid or reduce dose
when is prilocaine/octapressin used?
- If you wish to avoid Adrenaline
- Latex allergy
- Preservative allergy
when is prilocaine/octapressin avoided?
pregnancy
when is mepivacaine used?
alternative to prilocaine
when is articaine used?
– USP: diffusability, especially through bone
– Potential alternative to inferior alveolar blocks
when is reduced dose used due to caution?
– Liver disease – impaired metabolism
– Beta blockers
– Calcium Channel Blockers
– Drug abuse
what is articaine?
-3-propylamino-2-carbomethoxy-4- methylthiophene hydrochloride.
-Amide with an ester group
-Thiophene ring as its lipophilic
component – increases lipid solubility
Describe the metabolism of articaine.
- Plasma: plasma esterases
- Liver: hepatic enzymes
- elimination via kidneys
- Rapid breakdown – low systemic toxicity
what is a side effect of artcaine with mothers of new born children?
mothers should not breast feed for 48 hours following anaesthesia with Septanest
what is the maximum dosage of anaesthetic in articaine?
– Articaine Hydrochloride
– 4% = 40mg/ml (= 88mg in a 2.2ml cartridge)
what is the maximum dosage of vasoconstrictor in articaine?
– Adrenaline
- 1:100,000 = 10μg/ml
what preservative is used in articaine?
sodium metabisulphite
what is the maximum anaesthetic dose of articaine?
– 7mg/kg (up to a max of 300mg)
For what age is articaine not used?
Do not use in children <4 years
what 3 criteria’s are considered when evaluating if we need articaine as another short lasting anaesthetics?
- Efficacy-is it good as others
- does it have USP (unique selling point)
- Is it safe?
Is articaine as good as others (efficacy)?
-provided clinically effective pain relief during most dental procedures. Time to onset and duration of anaesthesia are appropriate for clinical use and comparable to those observed for other commercially available LA’s
Does articaine have a unique selling point?
- Ability to diffuse through bone
- Can achieve anaesthesia of lower posterior teeth by infiltration
what is efficacy of 4% articaine by infiltration comparable to?
2% lidocaine by inferior alveolar block injection
Is articaine safe?
-Rapid metabolism: – Plasma - esterases – Liver - amideases -Lower adrenaline concentrations – 1:100,000 or 1:200,000 -higher Anaesthetic concentrations 4% -no serious adverse effects
what is paraesthesia?
altered sensation
what are the frequencies of paraesthesia?
– Articaine -1:219,949
– Prilocaine-1:294,077
– Lidocaine- 1: 4,405,130
what causes paraesthesia?
-Physical trauma to nerve trunk
-Not likely due to articaine itself as it has the
lowest neurotoxicity when compared to
other drugs at the same concentration Werdehausen et
what does inferior alveolar blocks success depend largely on?
– accuracy of injection
– anatomy
– speed of injection…
– not diffusability through bone
when should articaine by avoided?
inferior alveolar injections
when is infiltration considered?
– failed IABs
– supplementing IABs
– to avoid IABs
