Drug interactions with LA

Question 1

How can practioners minimise the risk of drug interactions with LA?

Answer 1

• using an aspirating syringe; this reduces the likelihood of LA being administered directly into a blood vessel
• adhering to dosing recommendations in product literature

Question 2

What are the most commonly used amide LAs for dental procedures?

Answer 2

• lidocaine
• prilocaine
• articaine
• mepivacaine

Question 3

Where does evidence of potential interactions with LA dental preparations come from?

Answer 3

• they came from anecdotal case reports

Question 4

When are the drug interactions with LA, reported by the BNF, thought to be relevant?

Answer 4

when LA/ vasoconstrictors are used at high doses for specific indications other than dental anaesthesia

Question 5

State other clinical uses of lidocaine

Answer 5

• as treatment for arrhythmia - doses up to 1750 mg intravenously for over 24 hours

Question 6

Outline the dose of adrenaline used for anaphylaxis

Answer 6

500 mg IM

Question 7

Outline the dose of adrenaline used for cardiac arrest

Answer 7

1000 mg IV

Question 8

How much lidocaine (in mg) does a 2.2ml cartridge of 2% lidocaine in 1:80 000 solution contain?

Answer 8

44mg

Question 9

How much adrenaline (in mg) does a 2.2ml cartridge of 2% lidocaine in 1:80 000 solution contain?

Answer 9

27.5 mg

Question 10

How much lidocaine (in mg) does a 1.8ml cartridge of 2% lidocaine in 1:80 000 solution contain?

Answer 10

36mg

Question 11

How much adrenaline (in mg) does a 1.8ml cartridge of 2% lidocaine in 1:80 000 solution contain?

Answer 11

22.5mg

Question 12

What is the theoretical consequence of using/delivering more than one local anaesthetic agent (using a combination of local anaesthetic agents)?

Answer 12

• increased risk of myocardial depression
• increased risk of ventricular arrhythmia

Question 13

What is the consequence of using anti-arrhythmic doses of lidocaine with other anti-arrhythmic agents?

Answer 13

• may result in myocardial depression

Question 14

What is the consequence of using prilocaine with anti-arrhythmic agents?

Answer 14

myocardial depression

Question 15

What advice is given for the use of articaine for patients receiving anti-arrhythmic agents?

Answer 15

manufacture advises a caution when administering articaine in such cases

Question 16

Outline a relevant interaction between lidocaine and antibacterial drugs. State what antibacterials this interaction applies to

Answer 16

• increased risk of ventricular arrhythmia
• quinupristin
• dalfopristin

Question 17

State the relevant anti-bacterials with potential interaction with LAs

Answer 17

• quinupristin
• dalfopristin
• sulphonamides

Question 18

Outline the relevant interaction between prilocaine and antibacterials. State the antibacterial drug that this applies to

Answer 18

• increased risk of methaemoglobinaemia
• sulphonamindes e.g. co-trimoxazole

Question 19

Outline the relevant interaction between lidocaine and antipsychotic agents

Answer 19

• lidocaine at high doses can increase the risk of ventricular arrhythmia
• prolonged QT interval

Question 20

State the relevant anti-viral agents with potential interactions with LA agents

Answer 20

• fosamprenavir
• darunavir
• atazanavir
• lopinavir

Question 21

Outline the potential drug interaction between lidocaine and antiviral drugs

Answer 21

antiviral agents appear to increase plasma concentration of lidocaine and potentially increase cardiotoxicity

Question 22

Outline the drug interaction between lidocaine and betablockers

Answer 22

• high dose lidocaine with beta blockers can cause myocardial depression
• lidocaine clearance is reduced by propanolol; increases toxicity risk when lidocaine is given at high doses

Question 23

What is the effect of diuretics on lidocaine?

Answer 23

• action of lidocaine is antagonised by hypokalaemia caused by acetazolamide, loop diuretics or thiazides and related diuretics

Question 24

What is the interaction of lidocaine and 5HT3 antagonists such as dolasetron?

Answer 24

• increased risk of ventricular arrhythmia

Question 25

Outline the drug interaction between lidocaine and ulcer healing drugs such as cimetidine

Answer 25

* increased plasma concentrations of lidocaine; increased risk of toxicity when high doses of lidocaine are used * this effect is not seen with other ulcer healing drugs

Question 26

Outline the drug interaction between lidocaine and sedatives such as midazolam

Answer 26

* midazolam has been reported to cause a modest reduction in serum lidocaine levels but not mepivacaine levels

Question 27

Outline the nature of the drug interaction between local anaesthetic agents and TCAs

Answer 27

* increaed risk of hypertension and arrhtymias is high doses of adrenaline are given

Question 28

What is the clinically relevant dose of local anaesthetics if they are given to a patient on TCAs?

Answer 28

None if

Question 29

What is the clinically relevant dose of local anaesthetics if they are given to a patient on non-cardio-selective beta-blockers? State the non-cardio-selective beta blockers this applies to

Answer 29

None if

Question 30

Outline the nature of the reaction between beta-blockers and LA agents

Answer 30

* increased risk of severe hypertension * bradycardia when adrenaline is given with non-cardioselective beta-blocker

Question 31

What is the guidance for LA use with patients who abuse cocaine ?

Answer 31

avoid using LA containing adrenaline unless it is certain they have not used cocaine for 24 hours

Question 32

What is the nature of the interaction between LA agents and cocaine?

Answer 32

cocaine and adrenaline have sympathomimetic effects increase the risk of arrhythmias

Question 33

Outline the potential interaction between LA and clonidine

Answer 33

possible risk of hypertension when adrenaline is given with clonidine

Question 34

What is the clinically relevant dose of LA agents if administered to a patient on diuretics?

Answer 34

none if

Question 35

What is the guidance for the use of dopaminergics such as entacapone and LA ?

Answer 35

* no adverse reactions with entacapone have been reported in the dental setting * however it is a new drug an caution is vasoconstrictor dosing is required

Question 36

Outline the potential nature of the reaction between LA and entacapone

Answer 36

serum levels and therefore effects of adrenaline are possibly enhanced by entacapone

Question 37

The interaction between sympathomimetics and rasagiline (dopaminergic) are not clinically relevant in dentistry. True or false What is the guidance for use of sympathomimmetics and rasagiline

Answer 37

True avoid concomitant use of sympathomimetis with rasagiline sympathmimetics referred to here are those that are present in decongestant medication containing ephedrine or pseudoephedrine

Question 38

What is the nature of the reaction between LA agents and MAOI antidepressants?

Answer 38

co-administration of higher doses of adrenaline and MAOI antidepressants may produce hypotension or hypertension

Question 39

What is the nature of the interaction between higher doses of adrenaline and SNRIs/phenothiazines? Give examples of SNRI implicated in this

Answer 39

prolonged hypotension or hypertension * duloxetine * venlafaxine

Question 40

What is the clinically relevant dose of LA agents when considering its use with SNRIs or phenothiazines

Answer 40

none if doses of adrenaline do not exceed 50 mg /

Question 41

Warnings about the potential interaction between SNRIs/phenothiazines and LA only appear in product literature for ...

Answer 41

Lignospan Special

Question 42

Of the available vasoconstrictors (felypressin and adrenaline) only ________ is listed as interacting with other drugs

Answer 42

adrenline

Question 43

Although intraligamentary injection can result in rapid absorption into systemic circulation, why are LA levels unlikely to result in clinically significant drug interactions?

Answer 43

volumes used for intra-ligamentary injections are very small (0.2-0.5 ml; 2.5-6.25 mg of adrenaline respectively)

Question 44

Intra-osseous injection can lead to rapid absorption into systemic circulation. True or false

Answer 44

True

Question 45

Infiltration and regional block anaesthesia are not associated with significant systemic absorption. True or false

Answer 45

True

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• LA risks
• Drug interactions with LA
• Failure of LA 1
• Failure of LA 2
• Neurological Complications

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