Pharmacology for Dentistry

Muscle Relaxants 113

urine as the glucuronide and sulphate
conjugates of its metabolites. Small amount
is excreted in faeces.

Adverse effects include nausea,
anorexia, skin rash, vertigo, drowsiness,
headache and fever.

It is indicated in skeletal muscle spasm,
in surgery, orthopaedic procedures,
neurological diseases and tetanus.

CARISOPRODOL

It is used for the treatment of muscle
spasm. It has antipyretic and weak
antiadrenergic activity.

It is absorbed from the GI tract,
metabolised in the liver and excreted in urine
as metabolites including meprobamate.

It is used in musculoskeletal disorders.
Adverse reactions include nausea, rash,
headache, drowsiness, constipation and
dizziness.

ORPHENADRINE

It is a centrally acting, anticholinergic
muscle relaxant drug.

With administration of 100 mg of
orphenadrine, peak plasma concentration
are achieved within two hours. Half-life is
14 hours for the parent drug and 2 to 25
hours for the metabolites. Excretion is via
urine and faeces.

It is used in musculoskeletal disorders,
trauma, sports injuries, low backache,
tension headache, sprains and strains,
parkinsonism including the drug induced.

Adverse effects include dry mouth,
blurred vision, nausea, restlessness,
dizziness etc.

TIZANIDINE

Tizanidine is an α 2 -adrenergic receptor

agonist at supraspinal and spinal levels. This

effect results in inhibition of spinal

polysynaptic reflex activity. It presumably

reduces spasticity by increasing presynaptic

inhibition of motor neurons. Tizanidine has

no direct effect on skeletal muscle, the

neuromuscular junction or on monosynaptic

reflex activity.

In humans, tizanidine reduces

pathologically increased muscle tone,

including resistance to passive movements

and alleviates painful spasms and clonus.

Adverse effects include nausea, seda-

tion, dry mouth, dizziness, hypotension,

headache, palpitation. Other rarely pro-

duced side effects include hallucinations,

bradycardia etc.

It is indicated in spasticity due to

neurological disorders e.g., multiple sclerosis,

chronic myelopathy, degenerative diseases of

the spinal cord, cerebrovascular accidents

and cerebral palsy; painful muscle spasm

associated with static and functional

disorders of the spine (cervical and lumbar

syndromes); painful muscle spasm following

surgery e.g., for herniated intervertebral disc

or for osteoarthritis of the hip.

BACLOFEN

It is beta-4 (chlorophenyl)-gamma

aminobutyric acid. It is a powerful neuronal

depressant. It reduces the release of excita-

tory transmitter and is antinociceptive in

animal studies. It inhibits monosynaptic and

polysynaptic reflex transmission at spinal

level, probably by stimulating the GABAB