safety medical

Flexeril (Cyclobenzaprine) Side Effects

Flexeril i.e. cyclobenzaprine hydrochloride is a drug that is used in the management of spastic muscle disorders of acute onset. Despite its numerous clinical applications and efficacy, it appears that this drug has certain side-effects as well. In this article, we shall briefly review the adverse effects that are associated with the use of Flexeril.

Side-effects of Flexeril

Clinical trials have shown varying side-effects of Flexeril depending upon the dosage that is used for treatment. The common side-effects that patients will experience are drowsiness, dry mouth, fatigue and headache. The incidence of these side-effects is higher in patients taking 10 mg Flexeril as compared with those taking 5 mg.

In addition, patients also experience other side-effects in different systems.


Patients taking Flexeril may develop abdominal pain, diarrhoea, constipation, acid reflux disease, nausea and a feeling of being generally unwell. Patients may also experience increasing flatulence, gastritis and loss of appetite. Blood tests may demonstrate an abnormality in the liver function tests along with inflammation of the liver i.e. hepatitis. Jaundice may be seen on clinical examination.


Flexeril has been shown to cause irritability, nervousness and a reduction in mental acuity. Dizziness as mentioned above is an extremely common side-effect. Some patients have reported collapsing with loss of consciousness as well.


Though rare, patients taking Flexeril may develop an increase in heart rate or irregular heartbeats. Some patients may experience these in the form of palpitations. A low blood pressure may also occur and this is primarily due to the dilation of the blood vessels that is brought about by Flexeril.


Patients taking Flexeril may develop insomnia and depression. Hallucinations and psychosis have also been reported. Patients may experience vivid dreams which can be quite troublesome. Anxiety has been reported in some cases.


Flexeril can cause excessive sweating in some patients. Hair loss and sensitivity of skin to sunlight is a rare may occur.


Flexeril has been shown to cause depression of the bone marrow resulting in a low haemoglobin, low white cell count and low platelet count. These findings are of concern and require treatment and withdrawal of the drug. Small blots may be seen on the skin known as purpura.


Difficulty passing urine, impotence and swelling of the testes has been reported in patients taking Flexeril. Enlargement of breast tissue in men i.e. gynaecomastia and expression of milk through the breasts i.e. galactorrhoea may be seen but rarely.

Cyclobenzaprine side-effects are few and must be kept an eye out for when a patient is taking treatment. In the event of side-effect development, patients are requested to visit their health care practitioner for advice and possibility of ordering the medication.

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