A-Z Drug Facts > Cyclobenzaprine HCl

Cyclobenzaprine Hydrochloride

Pronouncation: (sye-kloe-BEN-za-preen HYE-droe-KLOR-ide)
Class: Skeletal muscle relaxant, centrally acting

Trade Names:
Amrix
- Capsules, extended-release 15 mg
- Capsules, extended-release 30 mg

Trade Names:
Cyclobenzaprine Hydrochloride
- Tablets 7.5 mg

Trade Names:
Flexeril
- Tablets 5 mg
- Tablets 10 mg

Apo-Cyclobenzaprine (canada)
Gen-Cyclobenzaprine (canada)
Novo-Cycloprine (canada)
Nu-Cyclobenzaprine (canada)
ratio-Cyclobenzaprine (canada)

Mechanism of Action

Pharmacology

Relieves skeletal muscle spasms of local origin without interfering with muscle function by acting within CNS at brain stem. Structurally and pharmacologically related to tricyclic antidepressants.

Pharmacokinetics

Absorption

Immediate-release (IR)

Mean oral bioavailability ranges from 33% to 55%. Reaches steady state in approximately 3 to 4 days following 3-times-daily dosing. C _max is approximately 12.8 to 46.1 ng/mL and AUC is approximately 80 to 319 ng•h/mL.

Extended-release (ER)

T _max is 7 to 8 h. C _max is 8 to 20 ng/mL. AUC is 354 to 780 ng•h/mL.

Distribution

Highly bound to plasma proteins.

Metabolism

Extensively metabolized, primarily to glucuronide-like conjugates.

Elimination

IR

Excreted primarily via kidneys. The t _½ is approximately 8 to 37 h.

ER

The t _½ is approximately 33 h.

Onset

1 h.

Duration

12 to 24 h.

Indications and Usage

Relief of muscle spasms associated with acute painful musculoskeletal conditions.

Unlabeled Uses

Treatment of fibrositis.

Contraindications

Standard considerations; use of MAOIs or within 14 days of their discontinuation; acute recovery phase of MI; arrhythmias; heart block or conduction disturbances; CHF; hyperthyroidism.

Dosage and Administration

Adults

PO

IR

5 to 10 mg 3 times daily.

ER

15 to 30 mg once daily.

General Advice

• Do not use longer than 3 wk.

Storage/Stability

Store at 59° to 86°F.

Drug Interactions

Alcohol and other CNS depressants

May cause additive CNS depression.

MAOIs

May cause hyperpyretic crisis, severe seizures, and death.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Palpitations (6%); arrhythmia, hypotension, syncope, tachycardia, vasodilation (postmarketing).

CNS

Somnolence (100%); drowsiness (39%); dizziness (19%); headache (17%); attention disturbance, tremor (6%); fatigue (3%); decreased mental acuity, irritability, nervousness (1% to 3%); abnormal sensations, abnormal thinking, agitation, anxiety, ataxia, depression, disorientation, dreaming, dysarthria, excitement, hallucinations, hypertonia, insomnia, malaise, paresthesia, psychosis, seizures, vertigo (postmarketing).

Dermatologic

Acne (6%); sweating (postmarketing).

EENT

Dry throat (8%); blurred vision (3%); pharyngitis (1% to 3%); ageusia, diplopia, tinnitus (postmarketing).

GI

Dry mouth (58%); nausea (8%); dysgeusia (6%); dyspepsia (4%); constipation (3%); abdominal pain, acid regurgitation, diarrhea (1% to 3%); anorexia, flatulence, gastritis, GI pain, thirst, tongue edema, vomiting (postmarketing).

Genitourinary

Urinary frequency, urinary retention (postmarketing).

Hepatic

Abnormal liver function, cholestasis, hepatitis, jaundice (postmarketing).

Hypersensitivity

Anaphylaxis (including angioedema), facial edema, pruritus, rash, urticaria (postmarketing).

Musculoskeletal

Local weakness, muscle twitching (postmarketing); myalgia.

Precautions

Pregnancy

Category B .

Lactation

Undetermined.

Children

Safety and efficacy in children younger than 15 yr of age not established.

Elderly

Do not use ER in elderly patients.

Hepatic Function

Do not administer ER to patients with hepatic function impairment.

Anticholinergic effects

Use with caution in patients with angle-closure glaucoma, increased IOP, and urinary retention.

Overdosage

Symptoms

Agitation, arrhythmia, ataxia, cardiac arrest, cardiac dysrhythmias, chest pain, CHF, coma, confusion, dilated pupils, dizziness, drowsiness, ECG changes (particularly in QRS axis), hyperactive reflexes, hyperpyrexia, hypertension, hypotension, hypothermia, nausea, neuroleptic malignant syndrome, seizures, slurred speech, stupor, tachycardia, tremor, visual hallucinations, vomiting.

Patient Information

• Inform patient that this medication makes injury temporarily feel better. Caution patient not to rush recovery and to avoid lifting or exercising too soon, which may damage muscles further.
• Caution patient to rise slowly from a sitting or standing position to avoid injury.
• Instruct patient to report the following symptoms to health care provider: confusion, difficulty urinating, fever, heart irregularities, palpitations, shortness of breath, weight gain, or yellowing of skin or eyes.
• Advise patient to take sips of water frequently, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs.
• Instruct patient to avoid alcoholic beverages or other CNS depressants while taking this medicine.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.

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