LOCAL ANAESTHETICS -1

Drug

Agent

Lignocaine

Bupivacaine

Ropivacaine

Class

Amide

Amide

Amide

Structure

Formulation

0.5/1/2% for iv +/- adr

2% gel, 10% spray

0.25%, 0.5%

+/- adr, +/- heavy

0.2/0.75/1%

Isomers

Nil

Racemic, levo less toxic

Pure levo enantiomer

P/kin

PKa

7.9

8.1

8.1

% unionised @pH7.4

25%

15%

15%

Lipid solubility

2.9

28

Protein binding %

70%

95%

94%

V_d (L/kg)

1.5

1

1

CL (ml/kg/min)

>bup

t_1/2 (hr)

1.5

3

2

Hepatic

N-dealkylation

N-dealkylation

N-dealkylation

Metabolites

NActive antiarrhythmic

Renal

Lung uptake

Yes

yes

Hydrolysis

Placental T/F (M:F)

.73

0.32

Admin

Dose (mg/kg)

Max dose (mg/kg)

3mg/kg

7mg/kg (adr)

2mg/kg

3mg/kg

Toxic plasma conc

3-5mcg/ml  CNS

10  seizures

25  CVS collapse

1.5mcg/ml

5  seizures

4mcg/ml

Onset (min)

5-15min

10-20min

10-15min

Duration (hrs)

1-2hr

4-8hr

4-8hr

P/dyn

Potency

1

4

4

Vasoactivity

V/d

V/d <>

V/c

Effect of Adren

 duration 50%

 sys absorption 1/3

CC:CNS

7

4

5

Allergy

Rare

Rare

Rare