preloder

Chlorzoxazone


Dosing

Adult Dose

:

Important Note:
Beers Criteria: Use caution or avoid use as potentially inappropriate in older adults.

Musculoskeletal pain; Acute:
500 to

750 mg

ORALLY 3 to 4 times daily.

Pediatric Dose

:

Important Note:
Beers Criteria: Use caution or avoid use as potentially inappropriate in older adults.

Indications
FDA-Labeled Indications:
Musculoskeletal pain; Acute
Mechanism of Action

Chlorzoxazone

is a centrally-acting agent used for treatment of painful musculoskeletal conditions. It inhibits multisynaptic reflex arcs primarily at the spinal cord and subcortical area of the brain resulting in reduced skeletal muscle spasm with relief of pain and increased muscle mobility
Adverse Effect
Common:
Cardiovascular:
Lightheadedness

Neurologic:
Dizziness
Excitement
Paradoxical
Somnolence

Other:
Malaise

Serious:
Gastrointestinal:
Gastrointestinal hemorrhage (rare)

Hepatic:
Hepatotoxicity (rare)

Immunologic:
Anaphylaxis (rare)

Interaction
CYP3A Inhibitors:
Eplerenone metabolism is predominantly mediated via CYP3A. Do not use INSPRA with drugs that are strong inhibitors of CYP3A .In post-MI CHF patients taking a moderate CYP3A inhibitor; do not exceed

25 mg

once daily. In patients with hypertension taking a moderate CYP3A inhibitor; initiate at

25 mg once daily

. For inadequate blood pressure response; dosing may be increased to a maximum of

25 mg twice daily



ACE Inhibitors and Angiotensin II Receptor Antagonists:
The risk of hyperkalaemia increase when eplerenone is used in combination with an ACE inhibitor and/or an ARB. A close monitoring of serum potassium and renal function is recommended; especially in patients at risk for impaired renal function; e.g.; the elderly

Lithium:
A drug interaction study of eplerenone with lithium has not been conducted. Lithium toxicity has been reported in patients receiving lithium concomitantly with diuretics and ACE inhibitors. Serum lithium levels should be monitored frequently if INSPRA is administered concomitantly with lithium.

Nonsteroidal Anti-Inflammatory Drugs (NSAIDs):
A drug interaction study of eplerenone with an NSAID has not been conducted. The administration of other potassium-sparing antihypertensives with NSAIDs has been shown to reduce the antihypertensive effect in some patients and result in severe hyperkalemia in patients with impaired renal function. Therefore; when INSPRA and NSAIDs are used concomitantly; monitor blood pressure and serum potassium levels

Phamacokinetics
Absorption:
Oral: time to peak concentration; 1 h to 2 h

Metabolism:
Hepatic: Rapidly Metabolized

Excretion:
Renal: Primarily as glucuronide; less than 1% unchanged

Precaution
Access:
While coadministration between medication-assisted treatment drugs (MAT; eg; methadone and buprenorphine) and benzodiazepines or other CNS depressants (including alcohol) may increase the possibility of harm; including

overdose

and death; concomitant therapy with MAT may be appropriate in some patients; if concomitant use is necessary; careful management and monitoring recommended.

Beers Criteria:
Avoid use in elderly patients as skeletal muscle relaxants are poorly tolerated in elderly and effectiveness at

tolerated doses

is questionable. Skeletal muscle relaxants with anticholinergic adverse effects cause sedation and increase the risk of fractures.
Discontinue if signs of liver dysfunction occur.
May have additive effects with central nervous system depressant drugs or alcohol

Pregnancy Category
Fetal Risk cannot be Ruled out
Breast Feeding
Infant risk cannot be ruled out
Monitoring
Reduction in pain and muscle spasms
Passive limb movement
Hepatic function
Dosage Form

Oral Tablet

:

250 mg


500 mg



Treatment
MANAGEMENT OF MILD TO MODERATE TOXICITY:
For mild to moderate exposures; good symptomatic and supportive care is the only necessary treatment. While decontamination may decrease the absorption of these drugs; it may not be necessary as most patients require little more than supportive care.

MANAGEMENT OF SEVERE TOXICITY:
For severe toxicity; administer intravenous fluids and vasopressors for hypotension; and endotracheal intubation and mechanical ventilation for severe CNS and respiratory depression. For seizures; administer benzodiazepines initially and add propofol or phenobarbital if seizures persist

Toxicology
ADULT:
Adults have developed CNS depression after ingestions of 8.5 to 21 g; but survived
with supportive care.
Patient Counselling or Clinical Teaching
Patient should avoid activities requiring mental alertness or coordination until drug effects are realized; as drug may cause light-headedness; dizziness; or somnolence
Inform patient that drug may discolor urine orange or red
This drug may cause malaise or overstimulation
Patient should report signs/symptoms of hepatotoxicity (fever; rash; anorexia; nausea; vomiting; fatigue; right upper quadrant pain; dark urine or jaundice) and immediately discontinue drug.
Tell patient to avoid concomitant use of CNS depressants; including alcohol; as this may cause additive CNS depression
Category of Chlorzoxazone :
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