What is the preferred route of administration for Myoril (Cyclobenzaprine), intramuscular (IM) or intravenous (IV)?

Myoril (Cyclobenzaprine) Is Not Available in IM or IV Formulations

Cyclobenzaprine is only available for oral administration—there are no intramuscular or intravenous formulations of this medication. 1, 2

Available Formulations and Dosing

Cyclobenzaprine hydrochloride is manufactured exclusively as:

• Oral tablets (5 mg, 10 mg) 1
• Oral extended-release capsules 1

The standard dosing regimen is:

• 5 mg three times daily (TID) is as effective as 10 mg TID with lower sedation rates 1
• 10 mg TID was the traditional dose but causes more sedation 1
• 2.5 mg TID was not significantly more effective than placebo 1

Clinical Evidence for Oral Route

Efficacy is established only for oral administration:

• Onset of relief occurs within 3-4 doses of the 5 mg regimen 1
• Duration of action is 4-6 hours 1
• Efficacy is independent of sedation, as demonstrated in patients who did not report somnolence 1
• Significantly superior to placebo in relieving acute skeletal muscle spasm 1, 2

Common Pitfall to Avoid

Do not confuse cyclobenzaprine with other muscle relaxants that have parenteral formulations. Some clinicians may mistakenly assume all muscle relaxants are available in injectable forms, but cyclobenzaprine has never been manufactured for IM or IV use 1, 2.

Alternative Parenteral Options

If parenteral muscle relaxation is required (e.g., patient cannot take oral medications), consider:

• Benzodiazepines (midazolam, lorazepam) available IM/IV 3, 4
• Methocarbamol (available IV, though not discussed in provided evidence)
• Other muscle relaxants with parenteral formulations

The choice should be based on the specific clinical scenario, with IM routes generally preferred over IV for safety when both are available 3, 5.