Drug of the month for June: 5 Points to Remember When Considering Amrix

by Alan Rook
PharmD, Clinical Pharmacist


This is the third post for our “Drug of the Month” blog. The medication that we’re highlighting is Amrix® (cyclobenzaprine extended-release). This drug was chosen based on the number of inquiries that our clinical department receives regarding this medication. One of the inquiries we receive is: is there a therapeutic alternative to Amrix® that might be more cost effective?

1. What is Amrix®?

Amrix® (cyclobenzaprine extended-release) is manufactured by Cephalon, Inc. and is FDA approved for muscle spasms “as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions.” It works by blocking nerve impulses that are sent to the brain.

Amrix® is an extended released capsule. It comes in 15 mg and 30 mg capsules. Usual dosing is a 15 mg capsule once daily, but some people may require 30 mg per day. Amrix is a brand drug and does not have a generic equivalent available. There is a therapeutic alternative—cyclobenzaprine immediate-release tablets—which come in 5 mg, 7.5 mg, and 10 mg tablets. The usual dose is 5 mg three times daily. As with Amrix, it may be necessary to increase to the 7.5 mg or 10 mg strength three times daily.meds

Common side effects for cyclobenzaprine containing products are:


2. Amrix Pricingheadache

The benefit of Amrix is the reduced pill burden on the injured worker, which may increase compliance with taking the medication although this comes with a significant cost: the average wholesale price of both Amrix 15 mg and 30 mg capsules is $30.14/capsule or $904.20 per month for a quantity of 30. (AWP may vary slightly based on manufacturer). However, if the injured worker is prescribed two 15 mg capsules (30 mg total) once daily, the cost is doubled–the price is $1,808.40 per month.

3. Therapeutic Alternative Pricing

Compare that price to the therapeutic alternative cyclobenzaprine at 5 mg with an AWP of $1.64 per tablet. Cyclobenzaprine is normally prescribed to be taken three times daily, so the monthly cost would be $147.60 for a monthly quantity of 90 tablets. The 7.5 mg tablet will be discussed in the Bonus section below. The 10 mg tablet has an AWP of $1.10/tablet, and it is normally prescribed to be taken three times daily, so the monthly cost would be $99.00 for a monthly quantity of 90 tablets. The difference could be as much as $1,709.40 if patients are prescribed two 15 mg of Amrix in comparison with three 10 mg of cyclobenzaprine.

4. Concerns with Amrix

A concern our clinical team has with this medication, and muscle relaxants in general, is that it is prescribed chronically—greater than 90 days. Based on the clinical studies that have been conducted with muscle relaxants, there are benefits associated with “short-term (2-3 weeks) treatment of muscle spasm associated with acute painful musculoskeletal conditions.” Because of the short course of therapy, the use of an extended-release medication does not make sense from a clinical perspective.

5. We have the following recommendations for treating physicians to consider:

*Switching to an immediate-release cyclobenzaprine tablet, and
*Reducing the number of tablets from a quantity of 90 to a quantity of 30 tablets for 30 days. This quantity will provide for one tablet three times daily for 10 days. This should be an appropriate amount to provide therapeutic benefit for an exacerbation of muscle spasms.

Fexmid Bonus:

Fexmid® (cyclobenzaprine 7.5 mg tablet) is manufactured by Shionogi Pharma and now has a generic equivalent tablet available. Fexmid was released as an alternative to the 5 mg and 10 mg tablets, but at a higher cost. A monthly regimen is roughly $500 and provides very little in therapeutic benefit. Furthermore, Fexmid has been tied to a recently published report looking at prescribing in California. Physicians were prescribing and dispensing this medication in the place of the less costly 5 mg and 10 mg cyclobenzaprine tablets. This allowed physicians to charge the much higher AWP to the payer. The generic version of Fexmid, known as cyclobenzaprine, has been on the market for a short period of time and is approximately $430 for a monthly regimen—which is still much higher than the 5 mg and 10 mg alternative doses of the same medication.