Nate
Lidocaine companying
has been used extensively for treatment of cardiac arrhythmias
2cute myocardial
ac-
rnfarction.
Theraperlticl-S and taxi? pizsma levels of iidocaine have been reported. _~onoetbylgiScir,exyxjrlidide (MEGX), ii dea&yiated metabofite formed tiIer the zdministz&ion of Iidocame, has been reported to be appro_xim&e:y 80 % as potent a~i antkrrhythmic agent zs the parent drug H hrle the dideserhylatei! metabolite &cicexy!idide (GX) had only about ZO% the potency&_ F-lrzher, MEGX hzxs been suggested as a. contribrrting factor in the accwrence of adve_=e reactions &a~ sanetimes zrrse after the zdministrztion oflidacame’. JTherefore, the monitoring of p&ma levels of Iidocaine and MEGX m postmyocardkl mfz~c~ion paiients receiving lidocaine may be of benefit in the control of antiarrhythmic
therapy.
A number of gas chromatographic (GC) methods have been reported for the dezermmation of Irdoczune alone6-lo, and of Edocaine 2nd its dezfkylated metaboj&S XL-14rn - bioIogkz4 mater&. The latter procedrrres, however, appear to suffer from some diszdvzntages. DE Ftia 2nd Brown” described a 10% UCW98 an c’nromosorb 5%’ system bit &he Iidocziine, MEGX and GX pezks were not completely resolLed 2nd no mentros was made of the accuracy af the me+&ad_ Keen&an and Bayes5 repo,5ed the qirantltzati~ e chramatogrqhy. ~ithaut the use of an internal standard, of heptaBrrarabntyryE
derivatives
of iidoczine
and
its metabalites.
Mass frqmezto-
grzphy w.zs the detection method used for the CX estimation of lidowne, MEGX and G-X as described by Strong and AtkinsonE 2nd Strang et 01.~. The stationaq p&se employed was 3% SE-3J-CBr-17 (6:I) coated on a Chromasorb support.
However, the peak shapes of the primary and secondary amine metabolites were asymmenicaI and the calibration citrve for MEGX was non-linear below about OS &ml_ kdjepon-Yamoah and Prescottf4 used a single-column temperature-programming technique to determine fidocaine and irs metabolites after they had been converted to their acetyf derivatives. This paper describes a quantitative method for the isothermal GC of underivatised fidocaine and _MEGX following extraction from plasma samples. _MATERITiU.S
AND
METHOES
_Ma&rials Lidoczine hydrochloride, MEGX hydrochloride and GX were supplied by Astra ChemicaIs (Sydney, Australia). Benzhexol hydrochloride (Cyanamid Australia, Melbourne, Australia) was used as an internal standard. All reagents and solvents were analytical reagent grade except dlethyt ether, uhich was anaesthetic grade (BP). The diethyl ether was distiied immediately before use. Ucon 75-H-90,000 (Ur:ion Carbide Australia, Sydney, Austrsrli2) ~2s the stationary phase employed.
A Hewlett-Packard Model 57iO A gas chromatograph equipped wtth a flame ionization detector was used. The column was glass (2.5 ft. x $ in. 0-D.) packed with 2 76 Icon 75H-90,000-2% KOH on X0-100 mesh Gas-Chrom Q (Applied Science Labs., State College. Pa., U.S.A.). A pan coating methodIS ustng methanol as the solvent was the procedure used to ~02~ the KOH and &on onto the solid support. The packed column was conditioned for 3 h at I%” (no nitrogen flow) followed by 18 h at f&Y (50 ml/min nitrogen fiow). The operating conditions were: injection port temperature, 250 ’ ; column temperature, I75 o ; detector temperature, 250” ; carrier gas (nitrogen) flow-rate, 50 mf!mm; hydrogen Bow-rate, 60 ml/min: air flow-rate, 240 mf/min. Exrractian procedure and sample preparafiou Plasma (I ml) and aqueous internal stzandard solution (5.0 pg/O.I mf) were placed in a f S-ml @ass-stoppered centrif&e tube. After addition of 0.5 ml of IO iK NaOH and 5 ml diethy ether the tube was mixed for 2 min (vortex tiser) and centrifuged for 5 tin at l5OU g. The tube was cooled in a dry ice-acetone bath for 1 tin and the ether layer decanted into a second 15mf glass-stoppered centrifuge tube containing I ml of a I rK HCI sotmion. The ether and HCl mixture was mixed (1 tin) and centrifuged as described above and the ether phase discarded. Following the addition of 0.5 mE 10 M N&X-I the aqueous phase was extracted wrth 5 ml diethyl ether by _mixing for 2 min. After centJifugation, the separated ether phase was transferred to a IS-ml tube with a l&l-,& elongated bubble at the base, a srlrca boiling chip was added and the ether was evaporated by immersion of the tube in a waterbath at 40”. When no liquid ether was left the tube was stoppered and ptunged into ice to condense the remaining ether vapour and wash down the sides of the tube. This evaporation and condensation procedure was repeated until approtimatefy 10 pf of ether solution remained and 5-10.~1 were injected into the gas chromatograph.
L
__---_
r;l_-_
wpMpn
,q..q,~-..a.
uli_--_l=LL
----
--t . . ...___... _______T
---....-1_1
__-c_
------“---~--
------=---_-
IMHu...-w”v’
_....--I_
__-_
_“__
_--c^
‘Y
-----..
-_L=L----- _--c__ --
_._._.__~-_-. --------..
\_
\\
1
-2.J
0
Y
- !Y)
!lJ
c,
E
_@aThe reproducibbility of rep&de analyses of phsma samples concentrations of the two compounds is recorded in T.&de I.
containing
different
pfasma ievels of iidocaine acd MEGX in patients who were being treated for cardiac ar&ythmias with intravenous Iidocake Inf~ions. Venotzs Hood sampIes were colIectzd in tubes containing LOOunits of ammozium heparin together with blood separ&an granules. PIasma was sep2rated by centrifugation as soon after sampling as pos$bEe and was stored at -20” u&Z assayed. k some cases blood samples were cokcted from the patients durmg &Se iidoczine infzzion. More commorify, hoxvever, Hood sz+mpIesxere cokcted poor to cessation of the infusion and for a number of &xxs subseauent to this. Tke plasma levels of lidocaine and MEGX in one patient in the Iatter category are ilhtsfrated in Fig. 4. No mteLfenng chromatographic peaks were noted in plasma sampfes obtained before commencement of Iidocaine therapy.
just
?Chemethod is sensitive and accurate for the determination of Iidocaine and MEGX in plasma and hzs been found to be satisfactory for clinica appfimtian. At c-d to quantitate GX in plasma since. as stated t&is stage the rechniqze has not been u,eariier, &is metibolite has much less pharmacological actiitity. flowever, if estimation of GX was re-eqnkedthe use of a more pafar organic solvent far extraction shocld be the only modScation necessary. The use of the KOH-treated sotid suppan in the GC system minimised adsorption of the amines and obviated the need for derivatisation praxdnres to ensure sqmmetic& peak shaps. The method has also been used to quantitare fidoezke and MEGX in urine.
193
it’0333 REFERENCES
f R. Gtielly.
J. 0.
van der Gio&eE,
A. P. Spivak and D. C. H&son,
-We@ Eizgf. J. Med.. 277
(1961) 1t15. 2 D. Z Jewiff, Y. Kishon 2nd M. Thomas, Lmzcet. i (196X) 266. 3 D. C.
E&L-+,ou
and E. L. AIderman,
Ln D. B. Scott and D. G. Jti (Editors), Lfdu~aine in rke Edinburgh, London, 1971, Ch. 18,
Trea;wznr of Kznrtictrfar Arrtk~tfmkr.s, E. & S. Lktigsto~e,
p. 186. 4 R. G. Bumey, C. A. Di F&o, M J. Peach, K. A. Petxie 2nd M. J. Skzste,; Amer. Heart J., SS (19741 765. 5 J. B. Keemaghan and R. N. Bones, J. Pimrmaco!. Exp. Ther.. 180 (1972) 454. 6 G. Svinhufmd, B. Orten_geu a;Id S. E. Jasobsson, Scared. J. C&L IL&. invesf., 17 (1965) 162. 7 J. B. Keenaghan, Anesfhesfology* 29 (1968) 110 8 F. ReynaIds and A. H. Beckert, J. Flrarm PharmacoL, 20 (1965) 7W. 9 M. Rowland, P. D. Thormon, A. Guichard and K. L. Mehnon, &IL N.Y. Acad SC& 179 (1971) 3s3. 10 N. Benotitz and M. Roshfand, Anestkesiofua, 39 (1973) 639. li C. A. Di Fans and R. E. Brouin, Anesthesfoiogy, 34 (1971) 86. I2 J. M. Strong and A. I_ Atkinson. Arzal. Ctreni.. 44 (1972) 2287. 13 5. hZ. Stmn~ M. Parker and _A_ J. Atkinsor, Clin. Pharmccaf. Tier.. 14 fL973) 67. 14 K. K. Adjepon-Yzmozfi znd L. F. Prescott, .f. Ptiarm Pirarmacof., 26 (1974) SS9. IS H. M. bfcNair and E. J Baneth, Basic Ca Chromatography, Varian-Aerogtzph, Wdnut
cam..
1968, p_ 6L2.
Cek.
Lidocaine companying
has been used extensively for treatment of cardiac arrhythmias
2cute myocardial
ac-
rnfarction.
Theraperlticl-S and taxi? pizsma levels of iidocaine have been reported. _~onoetbylgiScir,exyxjrlidide (MEGX), ii dea&yiated metabofite formed tiIer the zdministz&ion of Iidocame, has been reported to be appro_xim&e:y 80 % as potent a~i antkrrhythmic agent zs the parent drug H hrle the dideserhylatei! metabolite &cicexy!idide (GX) had only about ZO% the potency&_ F-lrzher, MEGX hzxs been suggested as a. contribrrting factor in the accwrence of adve_=e reactions &a~ sanetimes zrrse after the zdministrztion oflidacame’. JTherefore, the monitoring of p&ma levels of Iidocaine and MEGX m postmyocardkl mfz~c~ion paiients receiving lidocaine may be of benefit in the control of antiarrhythmic
therapy.
A number of gas chromatographic (GC) methods have been reported for the dezermmation of Irdoczune alone6-lo, and of Edocaine 2nd its dezfkylated metaboj&S XL-14rn - bioIogkz4 mater&. The latter procedrrres, however, appear to suffer from some diszdvzntages. DE Ftia 2nd Brown” described a 10% UCW98 an c’nromosorb 5%’ system bit &he Iidocziine, MEGX and GX pezks were not completely resolLed 2nd no mentros was made of the accuracy af the me+&ad_ Keen&an and Bayes5 repo,5ed the qirantltzati~ e chramatogrqhy. ~ithaut the use of an internal standard, of heptaBrrarabntyryE
derivatives
of iidoczine
and
its metabalites.
Mass frqmezto-
grzphy w.zs the detection method used for the CX estimation of lidowne, MEGX and G-X as described by Strong and AtkinsonE 2nd Strang et 01.~. The stationaq p&se employed was 3% SE-3J-CBr-17 (6:I) coated on a Chromasorb support.
However, the peak shapes of the primary and secondary amine metabolites were asymmenicaI and the calibration citrve for MEGX was non-linear below about OS &ml_ kdjepon-Yamoah and Prescottf4 used a single-column temperature-programming technique to determine fidocaine and irs metabolites after they had been converted to their acetyf derivatives. This paper describes a quantitative method for the isothermal GC of underivatised fidocaine and _MEGX following extraction from plasma samples. _MATERITiU.S
AND
METHOES
_Ma&rials Lidoczine hydrochloride, MEGX hydrochloride and GX were supplied by Astra ChemicaIs (Sydney, Australia). Benzhexol hydrochloride (Cyanamid Australia, Melbourne, Australia) was used as an internal standard. All reagents and solvents were analytical reagent grade except dlethyt ether, uhich was anaesthetic grade (BP). The diethyl ether was distiied immediately before use. Ucon 75-H-90,000 (Ur:ion Carbide Australia, Sydney, Austrsrli2) ~2s the stationary phase employed.
A Hewlett-Packard Model 57iO A gas chromatograph equipped wtth a flame ionization detector was used. The column was glass (2.5 ft. x $ in. 0-D.) packed with 2 76 Icon 75H-90,000-2% KOH on X0-100 mesh Gas-Chrom Q (Applied Science Labs., State College. Pa., U.S.A.). A pan coating methodIS ustng methanol as the solvent was the procedure used to ~02~ the KOH and &on onto the solid support. The packed column was conditioned for 3 h at I%” (no nitrogen flow) followed by 18 h at f&Y (50 ml/min nitrogen fiow). The operating conditions were: injection port temperature, 250 ’ ; column temperature, I75 o ; detector temperature, 250” ; carrier gas (nitrogen) flow-rate, 50 mf!mm; hydrogen Bow-rate, 60 ml/min: air flow-rate, 240 mf/min. Exrractian procedure and sample preparafiou Plasma (I ml) and aqueous internal stzandard solution (5.0 pg/O.I mf) were placed in a f S-ml @ass-stoppered centrif&e tube. After addition of 0.5 ml of IO iK NaOH and 5 ml diethy ether the tube was mixed for 2 min (vortex tiser) and centrifuged for 5 tin at l5OU g. The tube was cooled in a dry ice-acetone bath for 1 tin and the ether layer decanted into a second 15mf glass-stoppered centrifuge tube containing I ml of a I rK HCI sotmion. The ether and HCl mixture was mixed (1 tin) and centrifuged as described above and the ether phase discarded. Following the addition of 0.5 mE 10 M N&X-I the aqueous phase was extracted wrth 5 ml diethyl ether by _mixing for 2 min. After centJifugation, the separated ether phase was transferred to a IS-ml tube with a l&l-,& elongated bubble at the base, a srlrca boiling chip was added and the ether was evaporated by immersion of the tube in a waterbath at 40”. When no liquid ether was left the tube was stoppered and ptunged into ice to condense the remaining ether vapour and wash down the sides of the tube. This evaporation and condensation procedure was repeated until approtimatefy 10 pf of ether solution remained and 5-10.~1 were injected into the gas chromatograph.
L
__---_
r;l_-_
wpMpn
,q..q,~-..a.
uli_--_l=LL
----
--t . . ...___... _______T
---....-1_1
__-c_
------“---~--
------=---_-
IMHu...-w”v’
_....--I_
__-_
_“__
_--c^
‘Y
-----..
-_L=L----- _--c__ --
_._._.__~-_-. --------..
\_
\\
1
-2.J
0
Y
- !Y)
!lJ
c,
E
_@aThe reproducibbility of rep&de analyses of phsma samples concentrations of the two compounds is recorded in T.&de I.
containing
different
pfasma ievels of iidocaine acd MEGX in patients who were being treated for cardiac ar&ythmias with intravenous Iidocake Inf~ions. Venotzs Hood sampIes were colIectzd in tubes containing LOOunits of ammozium heparin together with blood separ&an granules. PIasma was sep2rated by centrifugation as soon after sampling as pos$bEe and was stored at -20” u&Z assayed. k some cases blood samples were cokcted from the patients durmg &Se iidoczine infzzion. More commorify, hoxvever, Hood sz+mpIesxere cokcted poor to cessation of the infusion and for a number of &xxs subseauent to this. Tke plasma levels of lidocaine and MEGX in one patient in the Iatter category are ilhtsfrated in Fig. 4. No mteLfenng chromatographic peaks were noted in plasma sampfes obtained before commencement of Iidocaine therapy.
just
?Chemethod is sensitive and accurate for the determination of Iidocaine and MEGX in plasma and hzs been found to be satisfactory for clinica appfimtian. At c-d to quantitate GX in plasma since. as stated t&is stage the rechniqze has not been u,eariier, &is metibolite has much less pharmacological actiitity. flowever, if estimation of GX was re-eqnkedthe use of a more pafar organic solvent far extraction shocld be the only modScation necessary. The use of the KOH-treated sotid suppan in the GC system minimised adsorption of the amines and obviated the need for derivatisation praxdnres to ensure sqmmetic& peak shaps. The method has also been used to quantitare fidoezke and MEGX in urine.
193
it’0333 REFERENCES
f R. Gtielly.
J. 0.
van der Gio&eE,
A. P. Spivak and D. C. H&son,
-We@ Eizgf. J. Med.. 277
(1961) 1t15. 2 D. Z Jewiff, Y. Kishon 2nd M. Thomas, Lmzcet. i (196X) 266. 3 D. C.
E&L-+,ou
and E. L. AIderman,
Ln D. B. Scott and D. G. Jti (Editors), Lfdu~aine in rke Edinburgh, London, 1971, Ch. 18,
Trea;wznr of Kznrtictrfar Arrtk~tfmkr.s, E. & S. Lktigsto~e,
p. 186. 4 R. G. Bumey, C. A. Di F&o, M J. Peach, K. A. Petxie 2nd M. J. Skzste,; Amer. Heart J., SS (19741 765. 5 J. B. Keemaghan and R. N. Bones, J. Pimrmaco!. Exp. Ther.. 180 (1972) 454. 6 G. Svinhufmd, B. Orten_geu a;Id S. E. Jasobsson, Scared. J. C&L IL&. invesf., 17 (1965) 162. 7 J. B. Keenaghan, Anesfhesfology* 29 (1968) 110 8 F. ReynaIds and A. H. Beckert, J. Flrarm PharmacoL, 20 (1965) 7W. 9 M. Rowland, P. D. Thormon, A. Guichard and K. L. Mehnon, &IL N.Y. Acad SC& 179 (1971) 3s3. 10 N. Benotitz and M. Roshfand, Anestkesiofua, 39 (1973) 639. li C. A. Di Fans and R. E. Brouin, Anesthesfoiogy, 34 (1971) 86. I2 J. M. Strong and A. I_ Atkinson. Arzal. Ctreni.. 44 (1972) 2287. 13 5. hZ. Stmn~ M. Parker and _A_ J. Atkinsor, Clin. Pharmccaf. Tier.. 14 fL973) 67. 14 K. K. Adjepon-Yzmozfi znd L. F. Prescott, .f. Ptiarm Pirarmacof., 26 (1974) SS9. IS H. M. bfcNair and E. J Baneth, Basic Ca Chromatography, Varian-Aerogtzph, Wdnut
cam..
1968, p_ 6L2.
Cek.
