Drugs are synthetic molecules that are meant to correct the altered physiology. Unfortunately, their healing capability comes up with some side effects that can be lethal in some cases. Even more surprising is the fact that an overdose of these drugs can put life-threatening impacts. Among these dangerous drugs, those that act upon CNS are posing the highest risk. One such class of drugs is called muscle relaxants. Many people experience muscle spasms, twitching, and other deformities. In these cases, muscle relaxants are mostly prescribed by physicians.

These drugs can be risky to some extent if misused. Their continuous use or an overdose can cause serious complications that could prove fatal. Flexeril is a drug belonging to the same class. Its effects on the body, and it is lethal or not will be the highlights of this article.


Flexeril is a brand name of cyclobenzaprine. It is a B category drug, which means that it can only be used upon producing a prescription. The drug belongs to the class of muscle relaxants.

Mode of action

Cyclobenzaprine, like other muscle relaxants, is only used orally. It is prepared in two formulations. In tablet form and extended-release capsular forms, their definitive mechanism of action is still unclear; however, the drug is considered to act on the brain stem. It works to seize the motor transmission to skeletal muscles by putting a stop to alpha and gamma neurons of the transmission pathway. However, full effects are still unclear that makes it risky to use the drug.

Can Flexeril kill you?

Half-life and elimination

The half-life of Flexeril ranges from 8 to 37 hours. The drug is metabolized mainly in the liver by the cytochrome enzymes and excreted in urine by the kidneys. Any delay in its removal from the body can pose a risk.

Use and effects

Most physicians prescribe Flexeril for muscle spasm due to acute musculoskeletal conditions. This is their only proven use, and any other purpose is yet unconfirmed and thus risky. The side effect profile of this drug includes headache, dizziness, drowsiness, dysphagia, nausea, constipation, dry mouth, and a few others.

Is Flexeril lethal?

Now that we’ve discussed the related details, a question still hits our brain. “Can Flexeril kill us?”. The answer to this is, “Yes.” The drug has complete capability like other drugs to pose lethal complications. The overdose and regular use of the drug can be fatal to a great extent. Such improper use can lead to multiple abnormalities that can cause death. 

These effects can be any one of the following.

1- Heart complications

As we discussed that cyclobenzaprine is supposed to act at the brain stem, which is the same area that controls the heart rate. An abnormal amount of this drug can thus interfere with brain stem transmission to the brain. As a result, irregular heartbeat, arrhythmia, bradycardia, or tachycardia can occur. A severe form of these irregularities can cause the death of the patient.

2- Respiratory irregularities

In a similar way that Flexeril affects heart rate, it can also compromise respiration. Difficulty in breathing, initially leading to a complete stoppage, can be a possible outcome of this drug.

3- Serotonin syndrome

Some cases of Flexeril overdose has shown symptoms of serotonin syndrome. Seizures, nausea, agitation, and hallucinations are reported effects of the drug overdose.

4- Drug interaction

Cyclobenzaprine can also induce dangerous drug interactions, especially with MAOIs. Also, its use with barbiturates, benzodiazepines, verapamil has shown exaggeration of adverse effects.

Thus the drug is very much likely to cause death in extreme cases. However, what doses and concentration are lethal are questions still to be discussed.

Lethal dose

3 to 5 times than the prescribed dose of Flexeril is considered to be an overdose. The drug comes up in 5,7 and 10 mg preparations. Thus one can have an idea of the overdose. Also, taking more tablets in a short time can be fatal. Flexeril must only be used to 1 to 2 weeks. A longer and regular use of the drug for a month or more can also be a life taking amount. However, all these amounts can vary in different individuals. A combination of age, sex, weight, other medical conditions, and genetic factors play a significant role in the determination of lethal dose.


Any initial overdose of Flexeril can be treated with appropriate treatment. The detoxification of the drug, along with the treatment of the symptoms, can completely cure a person. In cases of emergency, steps to prevent respiratory and cardiac extremes can be the best measures. Gastric lavage can help in preventing more absorption of the drug. Thus appropriate treatment is helpful in cases of overdose of the drug.