59
Muscle relaxants
Reactions may be
common
, uncommon,
life-threatening
, or
commonandlife-threatening.
baclofen
dantrolene sodium
mebeverine hydrochloride
orphenadrine
(See Chapter 60,
ANTIPARKINSONian DRUGS
)
ropinirole
(See Chapter 60,
ANTIPARKINSONian DRUGS
)
Combination products
None.
baclofen
Clofen, Lioresal, Lioresal Intrathecal,
Pacifen, Stelax
Pregnancy risk category B3
Use in sport: Permitted
Available forms
Intrathecal injection:
0.5 mg/mL, 10 mg/5
mL, 10 mg/20 mL
Tablets:
10 mg, 25 mg
Indications & dosages
➤
Spasticity in multiple sclerosis, spinal cord
injury—
Adults:
Initially, 5mg PO t.i.d. for 3 days, then
10 mg t.i.d. for 3 days, 15 mg t.i.d. for 3 days,
20 mg t.i.d. for 3 days. Dosage increased
based on response, up to maximum of 80
mg daily.
➤
Management of severe spasticity in
individuals who do not respond to or cannot
tolerate oral baclofen therapy—
Adults:
Screening phase—
After test dose
to check responsiveness, drug is given by
implantable infusion pump. Test dose is 1
mL of a 50-mcg/mL dilution administered
into intrathecal space by barbotage over
1 minute or more. Significantly decreased
severity or frequency of muscle spasm or
reduced muscle tone should appear within
4–8 hours. If response is inadequate, second
test dose of 75mcg/1.5mL is given 24 hours
after first. If response is still inadequate, final
test dose of 100 mcg/2 mL is given 24 hours
later. Individuals unresponsive to 100-mcg
dose should not be considered candidates
for implantable pump.
Maintenance therapy—
Initial dose is
titrated based on screening dose that
elicited an adequate response.This effective
dose is doubled and administered over 24
hours. However, if screening dose efficacy
was maintained for 12 hours or longer, dose
is not doubled. After first 24 hours, dose is
increased slowly as needed and tolerated
by 10–30% daily. During prolonged
maintenance therapy, daily dose may be
increased by 10–40% if needed; if person
experiences adverse effects, dosage may
be decreased by 10–20%. Maintenance
dosages have ranged from 12 to 1500
mcg daily; however, experience with
dosages over 1000 mcg daily is limited.
Most individuals need 300 to 800mcg daily.
Adjust-a-dose:
For individuals with
impaired renal function, oral and intrathecal
dose must be decreased.
Action
Hyperpolarises muscle fibres to reduce
impulse transmission. Appears to reduce
transmission of impulses from spinal cord
to skeletal muscle.
Route
Onset
Peak Duration
PO
Hrs–wks 2–3 hrs Unknown
Intrathecal
0.5–1 hr 4 hrs
4–8 hrs
Adverse reactions
CNS:
drowsiness, dizziness,
headache,
weak
ness,fatigue,
hypotonia,
confusion,
insomnia,
dysarthria,
seizures.
