Shelf Life of Muscle Relaxants

Health care providers often prescribe muscle relaxants, also known as skeletal muscle relaxants, to relieve stiffness, pain or discomfort caused by a strained, sprained or injured muscle 1. If you find that the prescription muscle relaxants in your medicine cabinet have passed their expiration date, consider possible changes in drug effectiveness and safety before taking them 1.

Commonly Presribed Muscle Relaxants

There are several generic and brand name prescription muscle relaxants on the market 1. Some of the most commonly prescribed relaxants for skeletal muscle pain are carisoprodol (under the brand name Soma), cyclobenzaprine (Flexeril and Amrix), metaxalone (Skelaxin) and methocarbamol (Robaxin) 1.

Expert Insight

The U.S. Food and Drug Administration (FDA) requires that most prescription and over-the-counter medications, including muscle relaxants, have an expiration date 1. This date is a conservative guide to the shelf life of the medication. According to FDA researchers, many drugs remain chemically stable and therefore maintain full potency and safety beyond the manufacturer's expiration dates. In the shelf life expectancy program (SLEP), the FDA looked at multiple lots of each of 122 medications that had been stored under ideal conditions in their original sealed containers and found that 88 percent were stable at least one year beyond their marked expiration date. There were no muscle relaxants among the tested drugs 1.

According to Johns Hopkins Health Alerts, medications that have been stored in good conditions should maintain all or most of their potency for at least a year or two following the expiration date.

Proper Storage and Shelf Life

Avoid storing muscle relaxants in hot or moist places such as the bathroom or in the kitchen near the sink, stove or dishwasher 1. Air, moisture, temperature extremes and light can cause medications to breakdown and lose their effectiveness. A dresser drawer away from the light is a good place to store medications. Ensure the bottles are tightly sealed after use to minimize exposure to the air, and keep your prescription in the original container or packaging in which you received it from the pharmacy. Most pharmacies use darkly colored plastic bottles to help protect the medication from light.

Risks of Taking Expired Medications

According to Annette Gbemunu, Pharm.D., medication effectiveness and safety are the two primary concerns when taking expired medications 3. In the case of muscle relaxants, ineffective pain management can lead to increased personal distress, loss of wages, missed school or decreased productivity if you go to work or school despite your discomfort 1. Disintegration or color change indicate changes in the pills' composition that may render the medication unsafe.

Cost vs. Effectiveness and Safety

The rising cost of prescriptions has many patients looking for ways to cut expenses. In the case of muscle relaxants, it is important that the medication is effective in providing optimal pain relief 1. Even if the pills appear to look fine, consider getting a new prescription. If you have any questions or concern about your muscle relaxant or any other prescription or over-the-counter medication, talk to your pharmacist.