Generic Name: carisoprodol (kar eye soe PROE dole) Brand Names: Soma, Vanadom
Carisoprodol is a centrally-acting skeletal muscle relaxant. It is a colorless, crystalline powder, having a mild characteristic odor and a bitter taste. Carisoprodol is slightly soluble in water and freely soluble in alcohol, chloroform and acetone. The drug’s solubility is practically independent of pH. Carisoprodol is marketed in the United States under the brand name Soma, and in the United Kingdom and other countries under the brand names Sanoma and Carisoma. The drug is available by itself or mixed with aspirin and in one preparation (Soma Compound With Codeine) along with codeine and caffeine as well.
In the United States, while carisoprodol is not a controlled substance under federal regulations, as of February 2010, carisoprodol is considered to be a schedule IV controlled substance by the states of Alabama, Arizona, Arkansas, Florida, Georgia, Hawaii, Indiana, Kentucky, Louisiana, Massachusetts, Minnesota, Mississippi, New Mexico, Nevada, Oklahoma, Oregon, Texas and West Virginia (scheduled using the states new controlled substance program which requires physicians to obtain, and include, a state “DPS” number as well as a DEA number on all controlled substances prescriptions) and Washington State. Respective state Boards of Pharmacy and controlled substance authorities. The rest of the United States, excluding the above named states, falls under the DEA scheduling for the drug, which considers carisoprodol a non-scheduled chemical, meaning that carisoprodol is considered a general prescription medication by the federal government of the United States, with oversight provided solely by the U.S. Food and Drug Administration (FDA).
SOMA (carisoprodol) Tablets are available as 250 mg and 350 mg round, white tablets. Carisoprodol is a white, crystalline powder, having a mild, characteristic odor and a bitter taste. It is slightly soluble in water; freely soluble in alcohol, in chloroform, and in acetone; and its solubility is practically independent of pH. Carisoprodol is present as a racemic mixture. Chemically, carisoprodol is N-isopropyl-2-methyl-2-propyl-1,3-propanediol dicarbamate and the molecular formula is C12H24N2O4, with a molecular weight of 260.33. The structural formula is:
SOMA is indicated for the relief of discomfort associated with acute, painful musculoskeletal conditions in adults.
SOMA should only be used for short periods (up to two or three weeks) because adequate evidence of effectiveness for more prolonged use has not been established and because acute, painful musculoskeletal conditions are generally of short duration.
DOSAGE AND ADMINISTRATION
The recommended dose of SOMA is 250 mg to 350 mg three times a day and at bedtime. The recommended maximum duration of SOMA use is up to two or three weeks.
HOW SUPPLIED
Dosage Forms And Strengths
250 mg Tablets: round, convex, white tablets, inscribed with SOMA 250
350 mg Tablets: round, convex, white tablets, inscribed with SOMA 350
Storage and Handling
250 mg Tablets: round, convex, white tablets, inscribed with SOMA 250; available in bottles of 100 (NDC 0037-2250-10) and bottles of 30 (NDC 0037-2250-30).
350 mg Tablets: round, convex, white tablets, inscribed with SOMA 350; available in bottles of 100 (NDC 0037-2001-01).
Carisoprodol is a muscle relaxer that works by blocking pain sensations between the nerves and the brain. Carisoprodol is used together with rest and physical therapy to treat injuries and other painful musculoskeletal conditions.
What is the most important information I should know about carisoprodol?
This medication may be habit-forming and should be used only by the person it was prescribed for. Carisoprodol should never be given to another person, especially someone who has a history of drug abuse or addiction. Keep the medication in a secure place where others cannot get to it. You may have withdrawal symptoms when you stop using carisoprodol after using it over a long period of time. Do not stop using this medication suddenly without first talking to your doctor. You may need to use less and less before you stop the medication completely. Carisoprodol can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid drinking alcohol. It can increase drowsiness and dizziness caused by carisoprodol.
What should I discuss with my healthcare provider before taking carisoprodol?
Do not use this medication if you are allergic to carisoprodol or meprobamate (Equanil, Miltown), or if you have porphyria.Before using this medication, tell your doctor if you are allergic to any drugs, or if you have:
- epilepsy or other seizure disorder;
- liver disease; or
- kidney disease.
If you have any of these conditions, you may need a dose adjustment or special tests to safely take carisoprodol.
This medication may be habit-forming and should be used only by the person it was prescribed for. Carisoprodol should never be given to another person, especially someone who has a history of drug abuse or addiction. Keep the medication in a secure place where others cannot get to it. You may have withdrawal symptoms when you stop using carisoprodol after using it over a long period of time. Withdrawal symptoms include stomach pain, sleep problems, headache, nausea, and seizure (convulsions). Do not stop using this medication suddenly without first talking to your doctor. You may need to use less and less before you stop the medication completely. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. It is not known whether carisoprodol passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby. Do not give this medication to a child younger than 12 years old..
Carisoprodol side effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using carisoprodol and call your doctor at once if you have any of these serious side effects:
- paralysis (loss of feeling);
- extreme weakness or lack of coordination;
- feeling light-headed, fainting;
- fast heartbeat;
- seizure (convulsions);
- vision loss; or
- agitation, confusion.
Less serious side effects may include:
- drowsiness, dizziness, tremor;
- headache;
- depression, feeling irritable;
- blurred vision;
- sleep problems (insomnia); or
- nausea, vomiting, hiccups, upset stomach.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
Clinical Studies Experience
Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect rates observed in practice.
The data described below are based on 1387 patients pooled from two double blind, randomized, multicenter, placebo controlled, one-week trials in adult patients with acute, mechanical, lower back pain. In these studies, patients were treated with 250 mg of SOMA, 350 mg of SOMA, or placebo three times a day and at bedtime for seven days. The mean age was about 41 years old with 54% females and 46% males and 74 % Caucasian, 16 % Black, 9% Asian, and 2% other.
There were no deaths and there were no serious adverse reactions in these two trials. In these two studies, 2.7%, 2%, and 5.4%, of patients treated with placebo, 250 mg of SOMA, and 350 mg of SOMA, respectively, discontinued due to adverse events; and 0.5%, 0.5%, and 1.8% of patients treated with placebo, 250 mg of SOMA, and 350 mg of SOMA, respectively, discontinued due to central nervous system adverse reactions.
Table 1 displays adverse reactions reported with frequencies greater than 2% and more frequently than placebo in patients treated with SOMA in the two trials described above.
Table 1. Patients with Adverse Reactions in Controlled Studies
| Adverse Reaction |
Placebo (n=560) n (%) |
SOMA 250 mg (n=548) n (%) |
SOMA 350 mg (n=279) n (%) |
| Drowsiness | 31 (6) | 73 (13) | 47 (17) |
| Dizziness | 11 (2) | 43 (8) | 19 (7) |
| Headache | 11 (2) | 26 (5) | 9 (3) |
Postmarketing Experience
The following events have been reported during postapproval use of SOMA. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Cardiovascular
Tachycardia, postural hypotension, and facial flushing.
Central Nervous System
Drowsiness, dizziness, vertigo, ataxia, tremor, agitation, irritability, headache, depressive reactions, syncope, insomnia, and seizures.
Gastrointestinal
Nausea, vomiting, and epigastric discomfort.
Hematologic
Leukopenia, pancytopenia
DRUG INTERACTIONS
CNS Depressants
The sedative effects of SOMA and other CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants) may be additive. Therefore, caution should be exercised with patients who take more than one of these CNS depressants simultaneously. Concomitant use of SOMA and meprobamate, a metabolite of SOMA, is not recommended.
CYP2C19 Inhibitors and Inducers
Carisoprodol is metabolized in the liver by CYP2C19 to form meprobamate. Co-administration of CYP2C19 inhibitors, such as omeprazole or fluvoxamine, with SOMA could result in increased exposure of carisoprodol and decreased exposure of meprobamate. Co-administration of CYP2C19 inducers, such as rifampin or St. John’s Wort, with SOMA could result in decreased exposure of carisoprodol and increased exposure of meprobamate. Low dose aspirin also showed an induction effect on CYP2C19. The full pharmacological impact of these potential alterations of exposures in terms of either efficacy or safety of SOMA is unknown.
Drug Abuse And Dependence
SOMA is not a controlled substance . Discontinuation of carisoprodol in animals or in humans after chronic administration can produce withdrawal signs, and there are published case reports of human carisoprodol dependence.
In vitro studies demonstrate that carisoprodol elicits barbiturate-like effects. Animal behavioral studies indicate that carisoprodol produces rewarding effects. Monkeys self administer carisoprodol. Drug discrimination studies using rats indicate that carisoprodol has positive reinforcing and discriminative effects similar to barbital, meprobamate, and chlordiazepoxide.
Mechanism of Action
The mechanism of action of carisoprodol in relieving discomfort associated with acute painful musculoskeletal conditions has not been clearly identified.
In animal studies, muscle relaxation induced by carisoprodol is associated with altered interneuronal activity in the spinal cord and in the descending reticular formation of the brain.
Pharmacodynamics
Carisoprodol is a centrally acting skeletal muscle relaxant that does not directly relax skeletal muscles.
A metabolite of carisoprodol, meprobamate, has anxiolytic and sedative properties. The degree to which these properties of meprobamate contribute to the safety and efficacy of SOMA is unknown.
Pharmacokinetics
The pharmacokinetics of carisoprodol and its metabolite meprobamate were studied in a crossover study of 24 healthy subjects (12 male and 12 female) who received single doses of 250 mg and 350 mg SOMA (see Table 2). The exposure of carisoprodol and meprobamate was dose proportional between the 250 mg and 350 mg doses. The Cmax of meprobamate was 2.5 ± 0.5 μg/mL (mean ± SD) after administration of a single 350 mg dose of SOMA, which is approximately 30% of the Cmax of meprobamate (approximately 8 μg/mL) after administration of a single 400 mg dose of meprobamate.
Table 2: Pharmacokinetic Parameters of Carisoprodol and Meprobamate (Mean ± SD, n=24)
| 250 mg SOMA | 350 mg SOMA | |
| Carisoprodol | ||
| Cmax (μg/mL) | 1.2 ± 0.5 | 1.8 ± 1.0 |
| AUCinf (μg*hr/mL) | 4.5 ± 3.1 | 7.0 ± 5.0 |
| Tmax (hr) | 1.5 ± 0.8 | 1.7 ± 0.8 |
| T1/2 (hr) | 1.7 ± 0.5 | 2.0 ± 0.5 |
| Meprobamate | ||
| Cmax (μg/mL) | 1.8 ± 0.3 | 2.5 ± 0.5 |
| AUCinf (μg*hr/mL) | 32 ± 6.2 | 46 ± 9.0 |
| Tmax (hr) | 3.6 ± 1.7 | 4.5 ± 1.9 |
| T½ (hr) | 9.7 ± 1.7 | 9.6 ± 1.5 |
Absorption
Absolute bioavailability of carisoprodol has not been determined. The mean time to peak plasma concentrations (Tmax) of carisoprodol was approximately 1.5 to 2 hours. Co-administration of a high-fat meal with SOMA (350 mg tablet) had no effect on the pharmacokinetics of carisoprodol. Therefore, SOMA may be administered with or without food.
Metabolism
The major pathway of carisoprodol metabolism is via the liver by cytochrome enzyme CYP2C19 to form meprobamate. This enzyme exhibits genetic polymorphism (see Patients with Reduced CYP2C19 Activity below).
Elimination
Carisoprodol is eliminated by both renal and non-renal routes with a terminal elimination half-life of approximately 2 hours. The half-life of meprobamate is approximately 10 hours.
Gender
Exposure of carisoprodol is higher in female than in male subjects (approximately 30-50% on a weight adjusted basis). Overall exposure of meprobamate is comparable between female and male subjects.
Patients with Reduced CYP2C19 Activity
SOMA should be used with caution in patients with reduced CYP2C19 activity. Published studies indicate that patients who are poor CYP2C19 metabolizers have a 4-fold increase in exposure to carisoprodol, and concomitant 50% reduced exposure to meprobamate compared to normal CYP2C19 metabolizers. The prevalence of poor metabolizers in Caucasians and African Americans is approximately 3-5% and in Asians is approximately 15-20%.
Clinical Studies
The safety and efficacy of SOMA for the relief of acute, idiopathic mechanical low back pain was evaluated in two, 7-day, double blind, randomized, multicenter, placebo controlled, U.S. trials (Studies 1 and 2). Patients had to be 18 to 65 years old and had to have acute back pain ( ≤ 3 days of duration) to be included in the trials. Patients with chronic back pain; at increased risk for vertebral fracture (e.g., history of osteoporosis); with a history of spinal pathology (e.g., herniated nucleus pulposis, spondylolisthesis or spinal stenosis); with inflammatory back pain, or with evidence of a neurologic deficit were excluded from participation. Concomitant use of analgesics (e.g., acetaminophen, NSAIDs, tramadol, opioid agonists), other muscle relaxants, botulinum toxin, sedatives (e.g., barbiturates, benzodiazepines, promethazine hydrochloride), and anti-epileptic drugs was prohibited.
In Study 1, patients were randomized to one of three treatment groups (i.e., SOMA 250 mg, SOMA 350 mg, or placebo) and in Study 2 patients were randomized to two treatment groups (i.e., SOMA 250 mg or placebo). In both studies, patients received study medication three times a day and at bedtime for seven days.
The primary endpoints were the relief from starting backache and the global impression of change, as reported by patients, on Study Day 3. Both endpoints were scored on a 5-point rating scale from 0 (worst outcome) to 4 (best outcome) in both studies. The primary statistical comparison was between the SOMA 250 mg and placebo groups in both studies.
The proportion of patients who used concomitant acetaminophen, NSAIDs, tramadol, opioid agonists, other muscle relaxants, and benzodiazepines was similar in the treatment groups.
The results for the primary efficacy evaluations in the acute, low back pain studies are presented in Table 3.
Table 3: Results of the Primary Efficacy Endpointsa in Studies 1 and 2
| Study | Parameter | Placebo | SOMA 250 mg |
SOMA 350 mg |
| Number of Patients | n=269 | n=264 | n=273 | |
| 1 | Relief from Starting Backache, Mean (SE)b | 1.4 (0.1) | 1.8 (0.1) | 1.8 (0.1) |
| Difference between SOMA and Placebo, Mean (SE)b (95% CI) | 0.4 (0.2, 0.5) | 0.4 (0.2, 0.6) | ||
| Global Impression of Change, Mean (SE)b | 1.9 (0.1) | 2.2 (0.1) | 2.2 (0.1) | |
| Difference between SOMA and Placebo, Mean (SE)b (95% CI) | 0.2 (0.1, 0.4) | 0.3 (0.1, 0.4) | ||
| Number of Patients | n=278 | n=269 | ||
| 2 | Relief from Starting Backache, Mean (SE)b | 1.1 (0.1) | 1.8 (0.1) | |
| Difference between SOMA and Placebo, Mean (SE)b (95% CI) | 0.7 (0.5, 0.9) | |||
| Global Impression of Change, Mean (SE)b | 1.7 (0.1) | 2.2 (0.1) | ||
| Difference between SOMA and Placebo, Mean (SE)b (95% CI) | 0.5 (0.4, 0.7) | |||
| a The primary efficacy endpoints (Relief from Starting Backache and Global Impression of Change) were assessed by the patients on Study Day 3. These endpoints were scored on a 5-point rating scale from 0 (worst outcome) to 4 (best outcome). b Mean is the least squared mean and SE is the standard error of the mean. The ANOVA model was used for the primary statistical comparison between the SOMA 250 mg and placebo groups. |
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Patients treated with SOMA experienced improvement in function as measured by the Roland-Morris Disability Questionnaire (RMDQ) score on Days 3 and 7.
What does my medication look like?
Carisoprodol is available with a prescription under the brand name Soma. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.
- Soma 350 mg – white, round tablets
