الفهرس 
Neuromuscular TransmissionOnly 14 pages are availabe for public view
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Abstract
Patients who are given anticonvulsant drugs (phenytoin and
carbarnazepine) more than 2 weeks are said to be receiving chronic antiepileptic therapy while those who are given less than 2 weeks are on
acute antiepileptic therapy. Both acute and chronic antiepileptic therapy
were observed to alter pharmacodynamic effects of muscle relaxants.
Chronic phenytoin or carbarnazepine therapy induced resistance to
muscle relaxants reflected as increased total dose requirements,
shortened dosing interval, and speeder recovery. Investigators suggested
several pharmacokinetic and pharmacodynamic explanations for
resistance to muscle relaxants. None provided the full explanation in all
situations.
The present study was done to study the effects of chronic phenytoin and chronic carbamazepine therapy on the pharmacodynamics of
atracurium and pancuronium muscle relaxants. The study included 120
patients of both sexes who were selected randomly with age range from
20 to 55 years. Their body weights were between 70 - 90 Kg body
weight. They were scheduled for neurosurgical procedures
Patients were divided into six groups. group I was control group
for groups II and ill. All three groups consisted of 20 patients each and
all received atracurium as a muscle relaxant. group II and group ill
received chronic phenytoin and chronic carbarnazepine therapy
respectively. group IV was control group for groups V and VI. All three
groups consisted of 20 patients each and all received pancuronium as a
muscle relaxant. group V and group VI received chronic phenytoin and
chronic carbarnazepine therapy respectively. therapeutic level of the anticonvulsant drugs and patients outside the
therapeutic level were excluded from the study.
Vital data in the form of mean blood pressure and heart rate were
measured before and after muscle relaxant injection. Both of which did not change by the use of chronic antiepileptics.
Neuromuscular monitoring using Datex Relaxograph was
carried out. 95% twitch depression duration in seconds represent the
onset, 25% recovery time represent duration in minutes, and recovery
index measured as the time from 25% to 75% recovery in minutes.
Chronic use of anticonvulsants showed no effect on the onset of both atracurium and pancuronium in all groups. For atracurium, the
onset was 179.9 ± 14.2 seconds in group I, 177.7 ± 16.8 seconds in
group IT, and 178.7 ± 16 seconds in group ill. For pancuronium, the
onset was 250.8 ± 66.6 seconds in group IV, 249 ± 65.2 seconds in
group V, and 249 ± 65.6 seconds in group VI. Shorter duration with
accelerated recovery, subsequently increased total dosage requirement,
and shorter recovery index were found in groups n and m in
comparison to group I, and in groups V and VI in comparison to
group IV. 25% recovery for atracurium was 27.9 ± 4.5, 13.7 ± 2.2, 13.9
± 2.5 minutes respectively in groups I, IT, and ill. Recovery index for
atracurium was 7.2 ± 0.8, 5.9 ± 0.3, 5.8 ± 0.3 minutes respectively in
groups I, IT, and ill. For groups IV, V, and VI, 25% recovery for
pancuronium was 50 ± 13, 43.7 ± 8.6, 30 ± 3 minutes respectively;
while recovery index for pancuronium was 48.6 ± 10.5, 28.8 ± 3.3, 16.2
± 7.3 minutes in groups IV, V, and VI respectively.