This document provides information on the onset, duration, side effects, overdose, contraindications, and mechanism of action of various drugs including midazolam, morphine, lignocaine, and bupivicaine. It also describes the management of local anesthetic systemic toxicity (LAST) which can occur from excessive plasma concentrations of local anesthetics due to inadvertent intravenous injection or absorption from the tissue injection site. The onset of effects ranges from 2-20 minutes depending on the route of administration. Side effects include nausea, vomiting, respiratory depression, and in higher doses, agitation and loss of consciousness. Local anesthetic toxicity can lead to cardiovascular collapse and death. Lipid emulsion is recommended as an antidote for

1. Drug Onset,peak Duration Side Effects Overdose Contraindications MOA Antidote
Midazolam
[5mg/5ml]
No needto
dilute
A/P:
0.1mg/kg
5mg max
dose
(usually
more not
needed)
Administer max
2.5mg/dose
every 5 minutes
until levelof
sedation
achieved
(monitor SpO2
and VS carefully)
IV 2m, 5m
IM 15min
Oral 20min
1-6 hour 1. Nausea
2. Vomiting
3. Restlessness
4. Severe
drowsiness
5. Memoryloss
Cardiorespirat
orydepression
(SpO2,BP, HR)
Anterograde
amnesia
1. Documented
hypersensitivity
2. Acute alcohol
intoxication,oron
otherCNS
depressants
3. Acute narrow
angle glaucoma
4. Cardiorespiratory
impairment
5. Kidney/liver
impairment
(caution)
Increases
frequencyof GABA
channel opening
Anxiolytic
Hypnotic
Myorelaxant
Anticonvulsant
Flumazenil
[0.5mg/5mL]
- GABA receptor
antagonist(competitive)
- 0.2mg IV over 15s, may
repeatat 1 minintervals,
not to exceed4 doses
(1mg)
Morphine
[10mg/1mL]
Dilute 1mL
with9cc NS
to make
10cc inone
syringe
A/P:
0.1mg/kg
10mg max
dose
Ceiling dose
imposedonly by
side effects
IV 2 m, 5-20m 1-2 hours 1. Constipation
2. Nausea
3. Vomiting
4. Dry mouth
CNS:
Confusion,
drowsiness,
myoclonus,
hallucinations,
pin-point
pupils,
GCS<12
Respiratory
depression
causing
asphyxiaand
death
(RR < 8, or
RR<12 AND
1. Documented
hypersensitivity
2. Kidney/liver
impairment
(caution)
3. Advanced
respiratory
insufficiency
4. Craniuminjuries,
raisedintracranial
pressure
Opioidreceptor
agonist
μ: CNS(analgesia,
sedation,euphoria,
respdepression)
GI (downregulates
myentericplexusin
intestinal tract)
κ: spinal analgesia,
miosis(pinpoint
pupils) and
psychotomimetic
effects.
Naloxone
[0.4mg/mL]
Competitive opioid
antagonist
0.4mg IV / IM/ SC repeat
every2 mins,max 10mg
(0.01mg/kg)
*If onlongterm opioidsthen
0.2mg IV / IM / SC
Indications:GCS<12,RR<8
Pediatrics:

2. (somnolence,
resp depression)
Administer max
2.5mg/dose
every 5 minutes
until levelof pain
reliefachieved
(monitor SpO2
and VS carefully)
cyanosedor
difficultto
rouse)
Minimum
lethal dose =
200mg
δ: analgesia 0.01mg/kg x1, if needed,
0.1mg/kg x1
CF of opioidoverdose:cold,clammyskin,flaccidmuscles,fluidinthe lungs,loweredbloodpressure,"pinpoint"ordilatedpupils,sleepinessleadingtostuporand
coma, slowedbreathing,andslowpulse rate.
Riker’ssedation-agitationscale

3. Drug Onset
(min)
Duration
(min)
Side Effects Overdose Max
dose
(mg/kg)
MOA CI Antidote
Lignocaine aka
lidocaine (1%
or 2%)
[200mg/10mL]
2 15-60 Dizziness,
paraesthesia,
euphoria
withnormal
therapeutic
doses§
Higherdoses
– confusion,
vertigo,
tinnitus&
nausea
LAST:
CNS toxicity
Tongue/perioral
numbness
lightheadedness
Tinnitus
Visual
disturbance
Muscular
twitching
Alteredmental
status,severe
agitation,LOC,
convulsions
CVS collapse:
Sinus
bradycardia,
conduction
blocks,
ventricular
tachyarrhythmia,
asystole
Death
3-5 Fast voltage Na+
channel blocker
(akaClass 1B
anti-arrhythmic
drug)
Orderof loss:
Pain�
temperature �
touch � pressure
- CVS:heartblock,
Adams-Stokes
syndrome,WPWS
- Concurrentuse of
ClassI
antiarrhythmics,
amiodarone use
prior
- Hypersensitivityto
corn (corn-derived
dextrose)
If circulatory
arrest,
IV infusion
20% lipid
emulsion
Bolus: 1.5
mL/kgover 1
minute
Infusion:
15mL/kg/H
(refer belowfor
details)
MOA: ‘lipid
sink’where
lipidemulsion
acts as sponge,
extractsthe LA
agent
(lipophilic
property) from
aqueouspart
of plasmaor
tissue,hence
reducing
effectivsLA
conc in plasma
Lignocaine
with
adrenaline
2 120-360 7 Adrenaline
causes
vasoconstriction.
Adrenalinewill
Do not use
lignocaine with
adrenaline to
infiltrate areaswith

4. reduce systemic
absorption,
maintaina
higher
anaesthetic
concentration
nearnerve fibres
and prolonglocal
anaesthetic
conduction
blockade.
an end-arterial
supply,suchas
fingers,toes,pinna,
penisandnose.
Local anaesthetic
allergy
(uncommon).
Bupivicaine
(0.25%)
Marcain
5 120-240 CVSfirst� CNS�
death
2.5

5. MANAGEMENT OF LAST (Local Anaesthetic Severe Toxicity)
Causedby excessive plasmaconcentration ofLA, due to:
1. InadvertentINTRAVASCULARinjectionof LA;or
2. LA absorptionfromtissue injectionsite