Skeletal Muscle Relaxants Agents

Prototype :
- methacarbamol (Robaxin), baclofen (Lioresal), dantrolene (Dantrium),
metaxalone (Skelaxin), orphanedrine (Norgesic), chlorzoxazone
Mechanism of actions:
- depress CNS
- inhibit calcium ion release in the muscle
- enhance the inhibitory action of GABA (gamma-amino butyric acid)
Indications :
- for acute musculoskeletal pain
- for muscle spasticity associated with multiple sclerosis, cerebral palsy, CVA, and
spinal cord injury.
Adverse effects :
- hypotonia, ataxia, hypotension, drowsiness
- blurred vision, bradycardia, depression, urine retention
Nursing considerations :
1. Caution clients that mental alertness may be impaired.
2. Monitor neuromuscular status, bowel and bladder functions.
3. Inform clients that maximum benefit of baclofen is attained for 1-2 months.
4. Reduce baclofen dosage gradually because of associated withdrawal symptoms :
Confusion, hallucinations, paranoia & rebound spasticity.




Anticonvulsants
Prototype :
a. Hydantoins - phenytoin (Dilantin)
b. Barbiturates - phenobarbital ( Luminal)
c. Miscellaneous
- carbamazepine (Tegretol), diazepam, clorazepate (Tranxene),
valproic acid (Dapakene), ethosuximide (Zarontin).
Mechanism of action :
- treat seizures by depressing abnormal neuronal activity in motor cortex.


Adverse effects :
- sedation & drowsiness, gingival hyperplasia
- diplopia, nystagmus, vertigo, dizziness
- thrombocytopenia, aplastic anemia
Nursing considerations :
1. Advise female clients to use contraceptives.
2. Inform clients taking phenytoin that harmless urine discoloration is common.
3. Warn clients with diabetes that hydantoins may increase blood sugar level and that
valproic acid may produce a false positive result in urine ketone test.
4. Teach clients receiving carbamazepine to identify symptoms of bone marrow
depressions.
5. Reassure that barbiturates are not addictive at a low dosage.
6. Avoid taking alcohol with barbiturates.
7. Administer IV phenytoin slowly to avoid cardiotoxicity.
8. Avoid mixing other drugs in same syringe with phenytoin.





Antiparkinsonian Agents
Prototype :
a. Anticholinergic agents
- trihexyphenidyl (Artane), benztropine (Congentin)
b. Dopaminergic agents
- Levodopa, carbidopa-levodopa (Sinemet), amantidine (Symmetrel),
pergolide (Permax), selegiline (Eldepryl), bromocriptine.
Mechanism of actions :
a. anticholinergic agents
- inhibit cerebral motor centers.
b. dopaminergic agents
- increasing dopamine concentrations or
enhancing neurotransmitter functioning.
Adverse effects of dopaminergic agents:
a. levodopa – nausea, vomiting, anorexia, orthostatic hypotension,
dark-colored urine and sweat
b. amantidine – ankle edema, constipation
c. bromocriptine – palpitations, tachycardia
Nursing considerations :
1. Give dopaminergic agents after meals to reduce GI symptoms.
2. Reassure client that levodopa may cause harmless darkening of urine and sweat.
3. Avoid taking Vit B6 (pyridoxine) with levodopa because it speed up metabolism.
4. Educate clients to minimize orthostatic hypotension.
5. Elevate leg to reduce ankle edema.