- Email: [email protected]
THE NEUROMUSCULAR INTERACTION OF PROPANIDID WITH SUXAMETHONIUM AND TUBOCURARINE
Brit. J. Anaesth. (1968), 40, 818
THE NEUROMUSCULAR INTERACTION OF PROPANIDID WITH SUXAMETHONIUM AND TUBOCURARINE BT F. RICHARD ELLIS SUMMARY
Suxamethonium produces a more prolonged period of apnoea after a propanidid induction of anaesthesia than after the same dose of suxamethonium following a barbiturate induction (Howells et al., 1964; Clarke, Dundee and Daw, 1964). The site of this potentiation has not so far been conclusively demonstrated and it is the purpose of this paper to present pharmacological evidence of a probable site and mechanism of action. Harnik (1964) reported the biphasic effect of propanidid on ventilation which is characterized by a period of hyperventilation followed by a variable period of respiratory depression proceeding frequently to complete apnoea. This finding could be explained by either a central or a peripheral site of action of propanidid. An increase in spinal reflexes in cats to whom propanidid had been given (FBA Pharmaceuticals, 1964, personal communication) similarly may result from a central or a peripheral site of action of the drug. Putter (1965) has shown that propanidid is rapidly destroyed in vitro by non-specific esterases and so it would be reasonable to postulate some anticholinesterase action in order to explain the potentiation of suxamethonium by a reduced rate of breakdown of the suxamethonium when in the presence of propanidid. A direct action of the barbiturates on striated muscle has been demonstrated (Kraatz and Gluckman, 1954) and an increased muscular response to electrical stimulation shown. A similar effect was reported with propanidid using a nerve muscle preparation in vitro (Ellis, 1967).
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
Twelve rat phrenic nerve-diaphragm preparations were used to investigate the neuromuscular interactions of propanidid, suxamethonium, tubocurarine and mipafox (an anticholinesterase compound). The potentiation of suxamethonium by propanidid was demonstrated to be a neuromuscular effect, and was increased by chemical inactivation of cholinesterase. A complex interaction between tubocurarine and propanidid was found. A hypothesis for these actions of propanidid is propounded.
The present paper reports the interaction of suxamethonium and propanidid, and the effect of an anticholinesterase compound on this interaction, in order to determine anticholinesterase action of propanidid at the neuromuscular junction. Similar experiments using tubocurarine and propanidid were also performed and the type and degree of interaction between these drugs in the region of the neuromuscular junction is reported. METHODS
Twelve rat phrenic nerve-diaphragm preparations similar to those described by Bulbring (1946) were used. Wistar rats weighing between 250 and 400 g were killed by a blow on the head, and the dissection and assembly of the left hemidiaphragm and phrenic nerve was completed in approximately 10 minutes. The preparation was continually gassed with 5 per cent carbon dioxide in oxygen and intermittently perfused with Kreb's solution of the following composition (mM): NaCl 118.4, K Q 4.7, C a d 2 2.6, KH.PO, 1.2, MgSO 4 1.2, NaHCO, 25.0, d-glucose 10.1. The Kreb's solution was heated to 37°C±0.5°C before entering the tissue bath (see figs. 1 and 2). The tissue bath had a volume which allowed 15 ml of solution to cover the tissue completely. The diaphragm was made to contract 12 times a minute by applying rectangular electrical imF. RICHARD ELLIS, M.B., CH.B., F.F.A.R.C.S., Department
of Pharmacology and Anaesthesia, University of Manchester, England. Present address: Department of Anaesthesia, University of Leeds, England.
NEUROMUSCULAR INTERACTION OF PROPANIDK)
819
Brodi* L«v«r
Phrenic Narve
pulses either through platinum electrodes to the phrenic nerve, or directly to the muscle through the two inverted platinum hooks used to secure the lower (costal) portion of the preparation in the tissue bath. The resulting muscular twitch caused a downward displacement of a Brodie lever which marked the smoked drum of a kymograph. The drug solutions used were all standardized and had the following compositions: (1) propanidid 100 mg in 100 ml of fresh Kreb's solution; (2) suxamethonium 20 mg in 100 ml of distilled water; (3) tubocurarine, 10 mg pure compound in 100 ml distilled water; (4) mipafox 10 mg to 1 litre of Kreb's solution giving a final concentration of 10 yug/ml (mipafox is a powerful irreversible organophosphorus anticholinesterase compound).
In most of the experiments a routine procedure was adopted. A dose of relaxant, measured by volume of the standard solution, was added at zero time to the tissue bath and a recording of the gradual fade in twitch height due to the developing neuromuscular block was made. The percentage reductions in twitch height at 2, 4, 6 and 8 minutes were measured and calculated. This control rate of fall was compared with that produced by adding the same dose of relaxant with propanidid. The doses of propanidid used were 200 fig, 400 /tg and 800 pg. There were, therefore, four possible treatments and each treatment was assessed four times in a Latin square format. Between treatments the tissue was washed four times with fresh Kreb's solution allowing 2 minutes for each wash. After this the tissue was left for 12 minutes before the next treatment. Throughout the whole cycle the electrical stimulation of the preparation was continued. The statistical analysis was by means of a oneway analysis of variance (Moroney, 1963) and the significance of the F ratio was taken from tables (Fisher and Yates, 1953).
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
Suction
1 Sagittal section of organ bath containing rat diaphragm-phrenic nerve preparation. Organ bath is attached to water bath maintained at 37 °C. Position of indirect stimulating electrodes on phrenic nerve shown. FIG.
FIG. 2 Front view of organ bath (front plate detached to show assembly). Position of rat diaphragm preparation marked by dotted line; position of direct stimulating electrodes shown.
BRITISH JOURNAL OF ANAESTHESI
820 RESULTS
There is little difference between the first three records but propanidid 800 fig produced a significantly greater neuromuscular blockade. T h : small differences between drug doses can be better appreciated in figure 8 in which the percentage inhibition is plotted against time as before. The control curve produced by tubocurarine 20 jug is the lower continuous line and does not significantly differ from the propanidid 400 jug with tubocurarine 20 fig curve. Potentiation of tubocurarine as shown by a shift of the curve upwards and to the left is produced by propanidid 800 fig, the upper continuous line in figure 8, and also but to a lesser extent by propanidid 200 fig, but not by the intermediate dose of 400 fig of propanidid. A comparison of figures 8 and 4 will demonstrate a smaller potentiation of tubocurarine 20 fig than suxamethonium 200 /tg by the same dose of 800 fig of propanidid. •
DISCUSSION
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
(1) A neuromuscular potentiation of suxamethonium by propanidid was conclusively shown. Figure 3 was taken from a typical experimental trace; at each arrow suxamethonium 200 fig was added, together with doses of propanidid which varied from 0 to 800 jug. The control rate of development of neuromuscular blockade due to 200 fig alone is shown on the right. The degree of potentiation can be appreciated in figure 4 which summarizes the results. The percentage inhibition at 2, 4, 6 and 8 minutes after the addition to the tissue bath of suxamethonium 200 fig and varying doses of propanidid is shown and the control curve produced by suxamethonium 200 /
The concentrations of propanidid chosen for these experiments are broadly similar to those which could be expected in vivo shortly after induction of anaesthesia, assuming that a normal clinical dose of propanidid is distributed throughout the extracellular fluid. Findings with suxamethonium confirm the clinical results but also show that suxamethonium is potentiated peripherally by a mechanism acting at the neuromuscular junction. The chosen dose of mipafox for these experiments completely inactivates cholinesterase at the neuromuscular junction as in this concentration A comparison of figures 4 and 6 reveals a more (10 /tg/ml) neostigmine was found not to antagmarked potentiation of suxamethonium by pro- onize the neuromuscular blocking properties of panidid 200 fig when in the presence of mipafox, tubocurarine. If propanidid had possessed anticholinesterase as in figure 6, the curve is moved further to the left. There is no significant difference between the activity which could have accounted for its poten400 /tg and the 800 fig propanidid curves in figure tiation of suxamethonium, inactivation of the 6, whereas in the absence of mipafox (fig. 4) there neuromuscular cholinesterase with mipafox would is a significant difference (P<0.01) between the reduce or abolish the potentiation of suxamethonium by propanidid. This was not found and so 400 fig and the 800 jug propanidid curves. (3) Doses of propanidid (0-800 fig) when propanidid has no demonstrable anticholinesterase combined with tubocurarine 20 fi% produced vary- activity. The presence of mipafox was associated with an ing degrees of neuromuscular blockade. Figure 7 was taken from an experimental trace and the increased potency of suxamethonium and also doses of propanidid and tubocurarine and the an increased potentiation of suxamethonium by propanidid. times of administration are marked.
821
/NEUROMUSCULAR INTERACTION OF PROPANIDID
3 Potentiation of suxamethonium (sux) by propanidid (prop). Smoked drum recording of rat diaphragm twitch following stimulation of phrenic nerve. Increasing rate of twitch fade with increasing dose of propanidid. FIG.
200pg.
PROP.
800(jg.
SUX.
200 pa
PROP.
X
*
.<
SUX.
200pg.
PROP
200pa-
SUX. 200pg.
z
o hO X
FIG. 4 Potentiation of effect of suxamethonium by propanidid. Rat diaphragm preparation. Graph showing increase in percentage inhibition of twitch with time for 200 jug suxamethonium (sux) alone and in combination with varying doses of propanidid (prop).
z
z UJ
U
10
TIME
IN
MINUTES
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
SUX.
822
BRITISH JOURNAL OF ANAESTHESIA
6 Potentiation of suxamethonium by propanidid in the presence of mipafox. Rat diaphragm. Graph showing increase in percentage inhibition of twitch with time for 100 /ig suxamethonium (S) alone and in combination with varying doses of propanidid (P); preparation treated with mipafox (M). FIG.
TIME
MINUTES
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
FIG. 5 Relationship between propanidid, mipafox and suxamethonium (sux) on the rat diaphragm. Preparation similar to fig. 3 but treated with mipafox in addition to suxamethonium and propanidid.
m
NEUROMUSCULAR INTERACTION OF PROPANIDID
7 Effect of propanidid on tubocurarine block. Rat diaphragm. Preparation similar to fig. 3 but treated with tubocurarine (dtc) and propanidid. FIG.
» PROP «00 KS
,t
• PROP 200 pg
n
+
PROP. 400 pg
ft ••
I* t
a
FIG. 8 Effect of combining tubocurarine and propanidid on muscle twitch height. Rat diaphragm preparation. Graph showing increase in percentage inhibition of twitch with time for 200 /ig fubocurarine (dtc) alone and in combination with varying doses of propanidid (prop).
The increased activity of propanidid in the presence of mipafox can be explained by a reduced breakdown of propanidid following the inactivation of the cholinesterase.
From investigations of the site of action of propanidid (Ellis, 1967) it was suggested that the drug acts on the general muscle cell membrane. It has been recognized for some time (Burns and Paton, 1951) that depolarizing relaxants, such as decamethonium, unlike tubocurarine, do not remain at the myoneural junction but depolarize the muscle cell membrane in the vicinity of the endplate. Thus propanidid could potentiate suxamethonium on the muscle cell membrane. The action of propanidid on the muscle cell membrane mimics the effect produced by increasing extracellular ionic potassium (Ellis, 1968, in preparation) which partially depolarizes the membrane. The most likely effect of propanidid is, therefore, to depolarize the muscle cell membrane partially, and this would potentiate the depolarization produced by suxamethonium in the vicinity of the endplate. In clinical practice Clarke, Dundee and Hamilton (1967) found that higher doses of tubocurarine were required following propanidid than following thiopentone. They suggested that this finding wai due to curare-like activity of thiopentone at the endplate (Gross and Cullen, 1943; Kraatz and Gluckman, 1954). The present results are only partially in agreement with clinical observations. Low concentrations of propanidid (fig. 8) potentiate tubocurarine (P<0.05) as do high concentrations of propanidid (P<0.01). The intermediate concentration used, however, did not potentiate tubocurarine and (after 2 minutes of interaction) even appeared to
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
-(top) dtc. » «
BRITISH JOURNAL OF ANAESTHESIA
824 reverse the activity of the tubocurarine (P<0.05). This finding suggests that propanidid may have two separate actions at the neuromuscular level, and a crucial experiment currently being performed is to determine the effects of propanidid on cell membrane electrical potentials. ACKNOWLEDGEMENTS
REFERENCES
Bulbring, E. (1946). Observations on the isolated phrenic nerve diaphragm preparation of the rat. Brit. J. Pharmacol., 1, 38. Burns, B. D., and Paton, W. D. M. (1951). Depolarisation of the motor-end-plate by decamethonium and acetylcholine. J. Physiol. (Land.), 115, 41. Clarke, R. S. J., Dundee, J. W., and Daw, R. H. (1964). Clinical studies of induction agents. X I : The influence of some intravenous anaesthetics on the respiratory effects and sequelae of suxamethonium. Brit. J. Anaesth., 36, 307. Hamilton, R. C. (1967). Interaction be tween induction agents and muscle relaxants. Anaesthesia, 22, 235. Ellis, F. R. (1967). The neuromuscular effects of propanidid. Brit. J. Anaesth., 39, 515. Fisher, R. A., and Yates, F. (1953). Statistical Tables for Agricultural, Biological and Medical Research. Edinburgh: Oliver and Boyd. Gross, E. G., and Cullen, S. C. (1943). The effects of anesthetic agents on muscular contraction. J. Pharmacol, exp. Ther., 78, 358. Harnik, E. (1964). A study of the biphasic ventilatory effects of propanidid. Brit. J. Anaesth., 36, 655.
L'INTERACTION NEUROMUSCULAIRE DU PROPANIDID AVEC SUXAMETHONIUM ET TUBOCURARINE SOMMAIRE
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
I would like to thank Professor H. Schnieden of the Department of Pharmacology, University of Manchester, for helpful criticism of this work and for providing the facilities, and Dr. A. R. Hunter for continued interest. As this work was done as a senior registrar in anaesthesia in Manchester, thanks are due to Dr. T. H. Chadwick and the Manchester Regional Hospital Board for release from clinical duties.
Howells, T. H., Odell, J. R., Hawkins, T. J., and Steare, P. A. (1964). An introduction to FBA.1420: a new non-barbiturate intravenous anaesthetic. Brit. J. Anaesth., 36, 295. Kraatz, C P., and Gluckman, M I. (1954). The action of barbiturates on the contractions of voluntary muscle. J. Pharmacol, exp. Ther., I l l , 120. Moroney, M. J. (1963). Facts from Figures. Harmondsworth, Middlesex: Penguin. Putter, J. (1965). Uber den fermentativen Abban des Propanidid; in Horatz, K., Frey, R., and Zindler, M., Die intravenose Kurznarkose mit dam neven Phenoxyessigsaurederivat Propanidol {EpontoT). Berlin: Springer.
Douze preparations nerf phrinique-diaphragme dc rats ont eti utilised pour dtudier l'interaction netircmusculaire de propanidid, suxamethonium, tubocurarine et rnipafox (une substance anticholinesterase). La potentialisation de suxamethonium par le propanidid a tt& prouvee etre un effet neuromusculaire, intensify par l'inactivation chimique de la cholinesterase. On a note" une interaction complexe entre tubocurarine et propanidid. L'auteur avance une hypothese au sujet de ces effets de propanidid. DIE NEUROMUSKULARE WECHSELWIRKUNG VON PROPANIDID MIT SUXAMETHONIUM UND TUBOCURARIN ZUSAMMENFASSUNG
Zur Untersuchung der neuromuskularen Wechselwirkungen von Propanidid, Suxamethonium, Tubocurarin und Mipafox (Anticholinesterase-Verbindung) wurden zwolf Nervus phrenicus-Diaphragma-Praparate von Ratten verwendet. Bei der Potenzierung von Suxamethonium durch Propanidid handelte es sich, wic gezeigt wurde, um einen neuromuskularen EffekL Dieser wurde gesteigert durch chemische Inaktivierung der Cholinesterase. Es wurde eine komplexe gegenseitige Beeinflussung von Tubocurarin und Propanidid gefunden. Zur Erklarung dieser Wirkungen von Propanidid wird eine Hypothese vorgelegt.
THE NEUROMUSCULAR INTERACTION OF PROPANIDID WITH SUXAMETHONIUM AND TUBOCURARINE BT F. RICHARD ELLIS SUMMARY
Suxamethonium produces a more prolonged period of apnoea after a propanidid induction of anaesthesia than after the same dose of suxamethonium following a barbiturate induction (Howells et al., 1964; Clarke, Dundee and Daw, 1964). The site of this potentiation has not so far been conclusively demonstrated and it is the purpose of this paper to present pharmacological evidence of a probable site and mechanism of action. Harnik (1964) reported the biphasic effect of propanidid on ventilation which is characterized by a period of hyperventilation followed by a variable period of respiratory depression proceeding frequently to complete apnoea. This finding could be explained by either a central or a peripheral site of action of propanidid. An increase in spinal reflexes in cats to whom propanidid had been given (FBA Pharmaceuticals, 1964, personal communication) similarly may result from a central or a peripheral site of action of the drug. Putter (1965) has shown that propanidid is rapidly destroyed in vitro by non-specific esterases and so it would be reasonable to postulate some anticholinesterase action in order to explain the potentiation of suxamethonium by a reduced rate of breakdown of the suxamethonium when in the presence of propanidid. A direct action of the barbiturates on striated muscle has been demonstrated (Kraatz and Gluckman, 1954) and an increased muscular response to electrical stimulation shown. A similar effect was reported with propanidid using a nerve muscle preparation in vitro (Ellis, 1967).
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
Twelve rat phrenic nerve-diaphragm preparations were used to investigate the neuromuscular interactions of propanidid, suxamethonium, tubocurarine and mipafox (an anticholinesterase compound). The potentiation of suxamethonium by propanidid was demonstrated to be a neuromuscular effect, and was increased by chemical inactivation of cholinesterase. A complex interaction between tubocurarine and propanidid was found. A hypothesis for these actions of propanidid is propounded.
The present paper reports the interaction of suxamethonium and propanidid, and the effect of an anticholinesterase compound on this interaction, in order to determine anticholinesterase action of propanidid at the neuromuscular junction. Similar experiments using tubocurarine and propanidid were also performed and the type and degree of interaction between these drugs in the region of the neuromuscular junction is reported. METHODS
Twelve rat phrenic nerve-diaphragm preparations similar to those described by Bulbring (1946) were used. Wistar rats weighing between 250 and 400 g were killed by a blow on the head, and the dissection and assembly of the left hemidiaphragm and phrenic nerve was completed in approximately 10 minutes. The preparation was continually gassed with 5 per cent carbon dioxide in oxygen and intermittently perfused with Kreb's solution of the following composition (mM): NaCl 118.4, K Q 4.7, C a d 2 2.6, KH.PO, 1.2, MgSO 4 1.2, NaHCO, 25.0, d-glucose 10.1. The Kreb's solution was heated to 37°C±0.5°C before entering the tissue bath (see figs. 1 and 2). The tissue bath had a volume which allowed 15 ml of solution to cover the tissue completely. The diaphragm was made to contract 12 times a minute by applying rectangular electrical imF. RICHARD ELLIS, M.B., CH.B., F.F.A.R.C.S., Department
of Pharmacology and Anaesthesia, University of Manchester, England. Present address: Department of Anaesthesia, University of Leeds, England.
NEUROMUSCULAR INTERACTION OF PROPANIDK)
819
Brodi* L«v«r
Phrenic Narve
pulses either through platinum electrodes to the phrenic nerve, or directly to the muscle through the two inverted platinum hooks used to secure the lower (costal) portion of the preparation in the tissue bath. The resulting muscular twitch caused a downward displacement of a Brodie lever which marked the smoked drum of a kymograph. The drug solutions used were all standardized and had the following compositions: (1) propanidid 100 mg in 100 ml of fresh Kreb's solution; (2) suxamethonium 20 mg in 100 ml of distilled water; (3) tubocurarine, 10 mg pure compound in 100 ml distilled water; (4) mipafox 10 mg to 1 litre of Kreb's solution giving a final concentration of 10 yug/ml (mipafox is a powerful irreversible organophosphorus anticholinesterase compound).
In most of the experiments a routine procedure was adopted. A dose of relaxant, measured by volume of the standard solution, was added at zero time to the tissue bath and a recording of the gradual fade in twitch height due to the developing neuromuscular block was made. The percentage reductions in twitch height at 2, 4, 6 and 8 minutes were measured and calculated. This control rate of fall was compared with that produced by adding the same dose of relaxant with propanidid. The doses of propanidid used were 200 fig, 400 /tg and 800 pg. There were, therefore, four possible treatments and each treatment was assessed four times in a Latin square format. Between treatments the tissue was washed four times with fresh Kreb's solution allowing 2 minutes for each wash. After this the tissue was left for 12 minutes before the next treatment. Throughout the whole cycle the electrical stimulation of the preparation was continued. The statistical analysis was by means of a oneway analysis of variance (Moroney, 1963) and the significance of the F ratio was taken from tables (Fisher and Yates, 1953).
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
Suction
1 Sagittal section of organ bath containing rat diaphragm-phrenic nerve preparation. Organ bath is attached to water bath maintained at 37 °C. Position of indirect stimulating electrodes on phrenic nerve shown. FIG.
FIG. 2 Front view of organ bath (front plate detached to show assembly). Position of rat diaphragm preparation marked by dotted line; position of direct stimulating electrodes shown.
BRITISH JOURNAL OF ANAESTHESI
820 RESULTS
There is little difference between the first three records but propanidid 800 fig produced a significantly greater neuromuscular blockade. T h : small differences between drug doses can be better appreciated in figure 8 in which the percentage inhibition is plotted against time as before. The control curve produced by tubocurarine 20 jug is the lower continuous line and does not significantly differ from the propanidid 400 jug with tubocurarine 20 fig curve. Potentiation of tubocurarine as shown by a shift of the curve upwards and to the left is produced by propanidid 800 fig, the upper continuous line in figure 8, and also but to a lesser extent by propanidid 200 fig, but not by the intermediate dose of 400 fig of propanidid. A comparison of figures 8 and 4 will demonstrate a smaller potentiation of tubocurarine 20 fig than suxamethonium 200 /tg by the same dose of 800 fig of propanidid. •
DISCUSSION
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
(1) A neuromuscular potentiation of suxamethonium by propanidid was conclusively shown. Figure 3 was taken from a typical experimental trace; at each arrow suxamethonium 200 fig was added, together with doses of propanidid which varied from 0 to 800 jug. The control rate of development of neuromuscular blockade due to 200 fig alone is shown on the right. The degree of potentiation can be appreciated in figure 4 which summarizes the results. The percentage inhibition at 2, 4, 6 and 8 minutes after the addition to the tissue bath of suxamethonium 200 fig and varying doses of propanidid is shown and the control curve produced by suxamethonium 200 /
The concentrations of propanidid chosen for these experiments are broadly similar to those which could be expected in vivo shortly after induction of anaesthesia, assuming that a normal clinical dose of propanidid is distributed throughout the extracellular fluid. Findings with suxamethonium confirm the clinical results but also show that suxamethonium is potentiated peripherally by a mechanism acting at the neuromuscular junction. The chosen dose of mipafox for these experiments completely inactivates cholinesterase at the neuromuscular junction as in this concentration A comparison of figures 4 and 6 reveals a more (10 /tg/ml) neostigmine was found not to antagmarked potentiation of suxamethonium by pro- onize the neuromuscular blocking properties of panidid 200 fig when in the presence of mipafox, tubocurarine. If propanidid had possessed anticholinesterase as in figure 6, the curve is moved further to the left. There is no significant difference between the activity which could have accounted for its poten400 /tg and the 800 fig propanidid curves in figure tiation of suxamethonium, inactivation of the 6, whereas in the absence of mipafox (fig. 4) there neuromuscular cholinesterase with mipafox would is a significant difference (P<0.01) between the reduce or abolish the potentiation of suxamethonium by propanidid. This was not found and so 400 fig and the 800 jug propanidid curves. (3) Doses of propanidid (0-800 fig) when propanidid has no demonstrable anticholinesterase combined with tubocurarine 20 fi% produced vary- activity. The presence of mipafox was associated with an ing degrees of neuromuscular blockade. Figure 7 was taken from an experimental trace and the increased potency of suxamethonium and also doses of propanidid and tubocurarine and the an increased potentiation of suxamethonium by propanidid. times of administration are marked.
821
/NEUROMUSCULAR INTERACTION OF PROPANIDID
3 Potentiation of suxamethonium (sux) by propanidid (prop). Smoked drum recording of rat diaphragm twitch following stimulation of phrenic nerve. Increasing rate of twitch fade with increasing dose of propanidid. FIG.
200pg.
PROP.
800(jg.
SUX.
200 pa
PROP.
X
*
.<
SUX.
200pg.
PROP
200pa-
SUX. 200pg.
z
o hO X
FIG. 4 Potentiation of effect of suxamethonium by propanidid. Rat diaphragm preparation. Graph showing increase in percentage inhibition of twitch with time for 200 jug suxamethonium (sux) alone and in combination with varying doses of propanidid (prop).
z
z UJ
U
10
TIME
IN
MINUTES
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
SUX.
822
BRITISH JOURNAL OF ANAESTHESIA
6 Potentiation of suxamethonium by propanidid in the presence of mipafox. Rat diaphragm. Graph showing increase in percentage inhibition of twitch with time for 100 /ig suxamethonium (S) alone and in combination with varying doses of propanidid (P); preparation treated with mipafox (M). FIG.
TIME
MINUTES
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
FIG. 5 Relationship between propanidid, mipafox and suxamethonium (sux) on the rat diaphragm. Preparation similar to fig. 3 but treated with mipafox in addition to suxamethonium and propanidid.
m
NEUROMUSCULAR INTERACTION OF PROPANIDID
7 Effect of propanidid on tubocurarine block. Rat diaphragm. Preparation similar to fig. 3 but treated with tubocurarine (dtc) and propanidid. FIG.
» PROP «00 KS
,t
• PROP 200 pg
n
+
PROP. 400 pg
ft ••
I* t
a
FIG. 8 Effect of combining tubocurarine and propanidid on muscle twitch height. Rat diaphragm preparation. Graph showing increase in percentage inhibition of twitch with time for 200 /ig fubocurarine (dtc) alone and in combination with varying doses of propanidid (prop).
The increased activity of propanidid in the presence of mipafox can be explained by a reduced breakdown of propanidid following the inactivation of the cholinesterase.
From investigations of the site of action of propanidid (Ellis, 1967) it was suggested that the drug acts on the general muscle cell membrane. It has been recognized for some time (Burns and Paton, 1951) that depolarizing relaxants, such as decamethonium, unlike tubocurarine, do not remain at the myoneural junction but depolarize the muscle cell membrane in the vicinity of the endplate. Thus propanidid could potentiate suxamethonium on the muscle cell membrane. The action of propanidid on the muscle cell membrane mimics the effect produced by increasing extracellular ionic potassium (Ellis, 1968, in preparation) which partially depolarizes the membrane. The most likely effect of propanidid is, therefore, to depolarize the muscle cell membrane partially, and this would potentiate the depolarization produced by suxamethonium in the vicinity of the endplate. In clinical practice Clarke, Dundee and Hamilton (1967) found that higher doses of tubocurarine were required following propanidid than following thiopentone. They suggested that this finding wai due to curare-like activity of thiopentone at the endplate (Gross and Cullen, 1943; Kraatz and Gluckman, 1954). The present results are only partially in agreement with clinical observations. Low concentrations of propanidid (fig. 8) potentiate tubocurarine (P<0.05) as do high concentrations of propanidid (P<0.01). The intermediate concentration used, however, did not potentiate tubocurarine and (after 2 minutes of interaction) even appeared to
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
-(top) dtc. » «
BRITISH JOURNAL OF ANAESTHESIA
824 reverse the activity of the tubocurarine (P<0.05). This finding suggests that propanidid may have two separate actions at the neuromuscular level, and a crucial experiment currently being performed is to determine the effects of propanidid on cell membrane electrical potentials. ACKNOWLEDGEMENTS
REFERENCES
Bulbring, E. (1946). Observations on the isolated phrenic nerve diaphragm preparation of the rat. Brit. J. Pharmacol., 1, 38. Burns, B. D., and Paton, W. D. M. (1951). Depolarisation of the motor-end-plate by decamethonium and acetylcholine. J. Physiol. (Land.), 115, 41. Clarke, R. S. J., Dundee, J. W., and Daw, R. H. (1964). Clinical studies of induction agents. X I : The influence of some intravenous anaesthetics on the respiratory effects and sequelae of suxamethonium. Brit. J. Anaesth., 36, 307. Hamilton, R. C. (1967). Interaction be tween induction agents and muscle relaxants. Anaesthesia, 22, 235. Ellis, F. R. (1967). The neuromuscular effects of propanidid. Brit. J. Anaesth., 39, 515. Fisher, R. A., and Yates, F. (1953). Statistical Tables for Agricultural, Biological and Medical Research. Edinburgh: Oliver and Boyd. Gross, E. G., and Cullen, S. C. (1943). The effects of anesthetic agents on muscular contraction. J. Pharmacol, exp. Ther., 78, 358. Harnik, E. (1964). A study of the biphasic ventilatory effects of propanidid. Brit. J. Anaesth., 36, 655.
L'INTERACTION NEUROMUSCULAIRE DU PROPANIDID AVEC SUXAMETHONIUM ET TUBOCURARINE SOMMAIRE
Downloaded from http://bja.oxfordjournals.org/ at Simon Fraser University on June 6, 2015
I would like to thank Professor H. Schnieden of the Department of Pharmacology, University of Manchester, for helpful criticism of this work and for providing the facilities, and Dr. A. R. Hunter for continued interest. As this work was done as a senior registrar in anaesthesia in Manchester, thanks are due to Dr. T. H. Chadwick and the Manchester Regional Hospital Board for release from clinical duties.
Howells, T. H., Odell, J. R., Hawkins, T. J., and Steare, P. A. (1964). An introduction to FBA.1420: a new non-barbiturate intravenous anaesthetic. Brit. J. Anaesth., 36, 295. Kraatz, C P., and Gluckman, M I. (1954). The action of barbiturates on the contractions of voluntary muscle. J. Pharmacol, exp. Ther., I l l , 120. Moroney, M. J. (1963). Facts from Figures. Harmondsworth, Middlesex: Penguin. Putter, J. (1965). Uber den fermentativen Abban des Propanidid; in Horatz, K., Frey, R., and Zindler, M., Die intravenose Kurznarkose mit dam neven Phenoxyessigsaurederivat Propanidol {EpontoT). Berlin: Springer.
Douze preparations nerf phrinique-diaphragme dc rats ont eti utilised pour dtudier l'interaction netircmusculaire de propanidid, suxamethonium, tubocurarine et rnipafox (une substance anticholinesterase). La potentialisation de suxamethonium par le propanidid a tt& prouvee etre un effet neuromusculaire, intensify par l'inactivation chimique de la cholinesterase. On a note" une interaction complexe entre tubocurarine et propanidid. L'auteur avance une hypothese au sujet de ces effets de propanidid. DIE NEUROMUSKULARE WECHSELWIRKUNG VON PROPANIDID MIT SUXAMETHONIUM UND TUBOCURARIN ZUSAMMENFASSUNG
Zur Untersuchung der neuromuskularen Wechselwirkungen von Propanidid, Suxamethonium, Tubocurarin und Mipafox (Anticholinesterase-Verbindung) wurden zwolf Nervus phrenicus-Diaphragma-Praparate von Ratten verwendet. Bei der Potenzierung von Suxamethonium durch Propanidid handelte es sich, wic gezeigt wurde, um einen neuromuskularen EffekL Dieser wurde gesteigert durch chemische Inaktivierung der Cholinesterase. Es wurde eine komplexe gegenseitige Beeinflussung von Tubocurarin und Propanidid gefunden. Zur Erklarung dieser Wirkungen von Propanidid wird eine Hypothese vorgelegt.