chlorzoxazone

Absorption: Readily absorbed after oral administration.

Distribution: Unknown.

Metabolism/Excretion: Mostly metabolized by the liver; <1% excreted unchanged in urine.

Half-Life: 1.1 hr.

Time/Action Profile ⬆ ⬇

(skeletal muscle effects)

ROUTE	ONSET	PEAK	DURATION
PO	within 1 hr	1–2 hr	3–4 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Porphyria.

Use Cautiously in:

Underlying cardiovascular disease;
Renal impairment
Hepatic impairment;
OB: Safety not established in pregnancy;
Lactation: Safety not established in breastfeeding;
Geri: Appears on Beers list. ↑ risk of anticholinergic adverse reactions, sedation, and fractures in older adults. Avoid use in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

Derm: allergic dermatitis

GI: constipation, diarrhea, GI BLEEDING, heartburn, nausea, vomiting

Hemat: AGRANULOCYTOSIS, anemia

Neuro: dizziness, drowsiness

Misc: HYPERSENSITIVITY REACTIONS (INCLUDING ANGIOEDEMA)

Interactions ⬆ ⬇

Drug-drug:

↑risk of CNS depression with other CNS depressants, including alcohol, antihistamines, antidepressants, sedative/hypnotics, or opioid analgesics.

Drug-Natural Products:

Concomitant use of kava-kava, valerian, skullcap, chamomile, or hops can ↑ CNS depression.

Route/Dosage ⬆ ⬇

PO (Adults ): 250–750 mg 3–4 times daily.
PO (Children ): 20 mg/kg or 600 mg/m²/day in 3–4 divided doses.

Availability ⬆ ⬇

(Generic available)

Tablets: 250 mg; 375 mg; 500 mg; 750 mg

Assessment ⬆ ⬇

Assess patient for pain, muscle stiffness, and range of motion before and periodically during therapy.
Geri: Assess geriatric patients for anticholinergic effects (sedation and weakness).

Lab Test Considerations:

Monitor liver enzymes (AST, ALT, alkaline phosphatase and bilirubin) periodically during prolonged therapy.

Implementation ⬆ ⬇

PO: May be administered with meals to minimize gastric irritation. Tablets may be crushed and mixed with food or liquid for ease of administration.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication as directed; do not take more than the prescribed amount. Missed doses should be taken within 1 hr of time ordered; otherwise, omit and return to normal dose schedule. Do not double doses.
Medication may cause drowsiness and dizziness. Caution patient to avoid driving or other activities requiring alertness until response to drug is known.
Instruct patient to notify health care professional if early signs and/or symptoms of hepatotoxicity (fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, jaundice); discontinue medication immediately if signs and symptoms occur.
Advise patient to avoid concurrent use of alcohol or other CNS depressants, including opioids with this medication; may cause overdose.
If constipation becomes a problem, advise patient that increasing fluid intake and bulk in diet and stool softeners may alleviate this condition.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

section name header

Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇