Cyclobenzaprine (Flexeril) is a prescription muscle relaxant used to relieve acute muscle spasms, stiffness, and discomfort. It is intended for short-term treatment, typically alongside rest and physical therapy. Determining the correct dosage must always be done by a healthcare provider. This information is for general understanding only and is not a replacement for professional medical advice.
Standard Single-Dose Recommendations
The dosage for the immediate-release (IR) formulation is typically taken three times per day. For most adults, the usual starting single dose is 5 milligrams (mg) taken orally. This initial lower dose helps the body adjust and allows a healthcare provider to assess the patient’s response and tolerance.
Based on the individual’s needs, the single dose may be increased up to a maximum of 10 mg. Taking a single dose higher than 10 mg is not generally recommended for the IR formulation. Since the dose is taken three times daily, the maximum recommended total daily intake is 30 mg.
Treatment duration is usually limited to no more than two to three weeks. Muscle spasms associated with acute musculoskeletal conditions often resolve within this timeframe. Adhering to the prescribed single-dose amount helps manage the risk of side effects like sedation, which can be more pronounced with higher doses.
Variables That Affect Individual Dosage
Standard single-dose recommendations are not universal, as several health factors can require a reduced or altered dosage. Elderly patients typically require a lower and less frequent dose due to physiological changes that affect drug processing. Slower metabolism and elimination can lead to higher concentrations of the drug remaining in the body for longer periods.
Liver function is another important variable because the liver is primarily responsible for breaking down cyclobenzaprine. Patients with mild liver impairment may be started on a reduced dose and monitored closely. The medication is generally not recommended for individuals with moderate or severe liver impairment due to the increased risk of drug accumulation and toxicity.
The use of other central nervous system (CNS) depressants also necessitates a careful review of the dose. Taking cyclobenzaprine with substances like alcohol, opioids, or certain antihistamines can produce additive sedative effects that increase the risk of over-sedation and impaired coordination. The immediate-release (IR) formulation differs from the extended-release (ER) formulation, which is often prescribed as a single dose of 15 mg to 30 mg taken once daily.
Recognizing and Responding to Excessive Intake
Taking a single dose that is too high can lead to toxicity or overdose. One of the most common signs of excessive intake is severe drowsiness, confusion, and agitation. Cardiovascular signs are also prominent and may include a fast or irregular heart rate, or significant changes in blood pressure.
More severe signs of toxicity can manifest as hallucinations, slurred speech, tremors, or seizures. These symptoms indicate that the central nervous system is being dangerously overwhelmed by the medication. A serious complication is the development of Serotonin Syndrome, particularly when cyclobenzaprine is combined with other serotonergic drugs like certain antidepressants or opioids.
Symptoms of Serotonin Syndrome include mental status changes like confusion and agitation, along with autonomic instability such as a rapid heart rate, heavy sweating, and fever. Neuromuscular abnormalities, including muscle stiffness, twitching, and a loss of coordination, are also characteristic signs of this life-threatening condition. If an overdose is suspected, or if any of these severe symptoms appear, immediate emergency medical attention is required.