390
P A R T 4
Drugs acting on the central and peripheral nervous systems
■■
The centrally-acting skeletal muscle relaxants
interfere with the reflexes that are causing the muscle
spasm.
■■
The centrally-acting skeletal muscle relaxants
cause central CNS depression, and the adverse
effects associated with them are related to the
CNS depression (insomnia, dizziness, confusion,
anticholinergic effects).
■■
The centrally-acting muscle relaxants are used for
the relief of discomfort associated with acute, painful
musculoskeletal conditions as an adjunct to rest,
physical therapy and other measures.
DIRECT-ACTING SKELETAL MUSCLE
RELAXANTS
The direct-acting skeletal muscle relaxants enter
the muscle to prevent muscle contraction directly.
Direct-acting skeletal muscle relaxants (Table 25.2)
include dantrolene (
Dantrium
) and botulinum toxin
type A (
Botox, Dysport
).
Therapeutic actions and indications
Dantrolene directly affects peripheral muscle contrac-
tion and has become important in the management
of spasticity associated with neuromuscular diseases.
Dantrolene acts within skeletal muscle fibres, interfer-
ing with the release of calcium from the muscle tubules
(see Figure 25.2). This action prevents the fibres from
contracting. Dantrolene does not interfere with neu-
romuscular transmissions, and it does not affect the
surface membrane of skeletal muscle. Botulinum toxin A
binds directly to the receptor sites of motor nerve termi-
nals and inhibits the release of acetylcholine, leading to
local muscle paralysis. This drug is injected locally and
used to paralyse or prevent the contractions of specific
muscle groups.
Long-term use of dantrolene commonly results in a
decrease of the amount and intensity of required care.
Continued long-term use is justified as long as the drug
reduces painful and disabling spasticity. This agent is
KEY POINTS
Care considerations for people receiving
centrally-acting skeletal muscle relaxants
Assessment: History and examination
■
■
Assess for contraindications or cautions for the
use of the drug, including any known allergies,
to prevent hypersensitivity reactions
; cardiac
depression, epilepsy, muscle weakness or rheumatic
disorder,
which could be exacerbated by the effects
of these drugs
; pregnancy or breastfeeding,
which
would be contraindications to use of the drugs
;
and renal or hepatic dysfunction,
which alter
metabolism and excretion of the drugs
.
■
■
Assess temperature; skin colour and lesions;
CNS orientation, affect, reflexes, bilateral grip
strength and spasticity evaluation; bowel sounds
and reported output; and liver and renal function
tests
to determine baseline status before beginning
therapy and for any potential adverse effects.
Implementation with rationale
■
■
Provide additional measures to relieve
discomfort—heat, rest for the muscle, NSAIDs,
positioning—
to augment the effects of the drug at
relieving the musculoskeletal discomfort.
■
■
Discontinue drug at any sign of hypersensitivity
reaction or liver dysfunction
to prevent severe
toxicity.
■
■
If using baclofen, taper the drug slowly over 1 to
2 weeks
to prevent the development of psychoses
and hallucinations.
Use baclofen cautiously in
people whose spasticity contributes to mobility,
posture or balance
to prevent loss of this function.
■
■
If person is receiving baclofen through a delivery
pump, the person should understand the pump,
the reason for frequent monitoring and how to
adjust the dose and program the unit
to enhance
knowledge and promote compliance.
■
■
Monitor respiratory status
to evaluate adverse
effects and arrange for appropriate dose
adjustment or discontinuation of the drug.
■
■
Provide thorough teaching, including drug name,
prescribed dosage, measures for avoidance of
adverse effects, warning signs that may indicate
possible problems and the need for monitoring
and evaluation
to enhance knowledge about drug
therapy and to promote compliance.
■
■
Offer support and encouragement
to help the
person cope with the drug regimen.
Evaluation
■
■
Monitor response to the drug (improvement in
muscle spasm and relief of pain; improvement
in muscle spasticity).
■
■
Monitor for adverse effects (CNS changes, GI
depression, urinary urgency).
■
■
Evaluate the effectiveness of the teaching plan
(person can give the drug name and dosage,
name possible adverse effects to watch for and
specific measures to prevent them and describe,
if necessary, proper intrathecal administration).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
