Some muscle relaxers are controlled substances, but most are not. Out of the dozen or so muscle relaxants commonly prescribed in the United States, only one, carisoprodol (sold as Soma), is federally classified as a controlled substance. Benzodiazepines like diazepam (Valium) are also controlled and sometimes prescribed for muscle spasms, though they’re primarily anxiety medications. The rest, including popular options like cyclobenzaprine, baclofen, tizanidine, and methocarbamol, are not subject to the Controlled Substances Act.
Which Muscle Relaxers Are Controlled
Carisoprodol is the only dedicated muscle relaxant that carries a federal controlled substance classification. The DEA placed it on Schedule IV in January 2012 after reviewing evidence of abuse, dependence, withdrawal, and criminal diversion. The drug’s abuse potential comes from the way it and its breakdown product, meprobamate, affect the same brain signaling pathways as barbiturates. Meprobamate itself was introduced as an anti-anxiety drug in the 1950s and has been a Schedule IV substance for decades.
Diazepam (Valium) is the other name that comes up frequently. It’s a benzodiazepine, also Schedule IV, and the FDA approves it as an add-on treatment for skeletal muscle spasm caused by injury, inflammation, or neurological conditions like cerebral palsy. But diazepam is a benzodiazepine first and a muscle relaxant second. Doctors prescribe it far more often for anxiety or seizures than for muscle problems. Other benzodiazepines like clonazepam and lorazepam are Schedule IV as well, though they’re rarely used specifically as muscle relaxants.
Common Muscle Relaxers That Are Not Controlled
The muscle relaxants you’re most likely to receive for a back injury or muscle spasm are not controlled at the federal level. These include:
- Cyclobenzaprine (Amrix, Flexeril): the most widely prescribed muscle relaxant in the U.S., used for acute musculoskeletal pain
- Methocarbamol (Robaxin): commonly used for short-term muscle spasm relief
- Tizanidine (Zanaflex): prescribed for both muscle spasms and spasticity
- Baclofen (Lioresal): mainly used for spasticity from conditions like multiple sclerosis or spinal cord injuries
- Metaxalone (Skelaxin): another option for acute musculoskeletal pain
- Dantrolene (Dantrium): used for spasticity and malignant hyperthermia
None of these are listed on the DEA’s controlled substance schedules. Your pharmacy can refill them without the same restrictions that apply to controlled drugs, and your doctor can call them in or send electronic prescriptions with fewer regulatory hurdles.
Why the Distinction Matters for Your Prescription
If your muscle relaxer is a Schedule IV controlled substance, federal law caps your prescription at five refills within six months of the date it was written. After that, your doctor has to write an entirely new prescription. You can’t stockpile refills or use an old prescription that’s more than six months past its issue date.
Non-controlled muscle relaxants don’t carry these federal refill limits. Your doctor and pharmacy follow state regulations and their own clinical judgment on how many refills to authorize, which typically means fewer trips to get a new prescription. Electronic prescribing and phone-in refills are also simpler for non-controlled medications in many states.
Two Categories With Different Risks
Muscle relaxants fall into two broad categories that help explain why some carry more risk than others. Antispasmodics work in the brain and spinal cord to reduce muscle spasms, typically from injuries or acute back pain. This group includes carisoprodol, cyclobenzaprine, methocarbamol, and metaxalone. Antispastics act on the spinal cord or directly on muscle fibers to reduce the constant tightness seen in neurological conditions. Baclofen and dantrolene are the main antispastics.
The antispasmodic group carries more concern about sedation and, in some cases, dependency. Carisoprodol stands out because of how strongly it affects brain chemistry through the same pathways targeted by barbiturates and older sedatives. Cyclobenzaprine, while not federally controlled, still has precautions around misuse noted in prescribing guidelines. None of these drugs are considered first-line pain treatment specifically because of their side effect profiles, including drowsiness, dizziness, and the potential for dependence with prolonged use.
State Laws Can Add Restrictions
Federal scheduling sets a floor, not a ceiling. Individual states can classify drugs more strictly than the DEA does. Some states have placed additional restrictions on muscle relaxants that aren’t federally controlled, or have added monitoring requirements. For example, several states require muscle relaxants to be reported to their prescription drug monitoring programs even when the drug isn’t a federal controlled substance. If you’re unsure about your state’s rules, your pharmacist can tell you whether your specific medication carries any extra requirements where you live.
Dependence Risk Even Without Scheduling
A drug not being “controlled” doesn’t mean it’s risk-free. Cyclobenzaprine, methocarbamol, and other non-controlled muscle relaxants all carry precautions about potential misuse. Physical dependence can develop with regular use of several muscle relaxants, controlled or not, especially when taken longer than the two to three weeks typically recommended for acute pain. Stopping abruptly after prolonged use can cause withdrawal symptoms including trouble sleeping, nausea, and headaches. This is one reason doctors generally prescribe muscle relaxants for short courses rather than ongoing therapy.