Tenoxicam is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the oxicam class that has established itself as an important therapeutic option for various inflammatory conditions. First patented by Roche in 1974 and approved for medical use in 1987, tenoxicam has become available under various brand names across many countries worldwide, though notably not in the United States.
This medication provides anti-inflammatory, analgesic, and antipyretic effects through selective inhibition of prostaglandin synthesis. With its long half-life enabling once-daily dosing, tenoxicam offers convenience while effectively managing pain and inflammation associated with various musculoskeletal disorders.
Introduction to Tenoxicam
Tenoxicam, sold under the brand name Mobiflex among others, is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the oxicam group. It is primarily prescribed to relieve inflammation, swelling, stiffness, and pain associated with rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, tendinitis, bursitis, and periarthritis of the shoulders or hips. The drug exhibits anti-inflammatory, analgesic, and antipyretic properties, making it versatile for treating both acute and chronic inflammatory conditions.
Tenoxicam was developed as an alternative to existing NSAIDs, with its primary advantage being a long elimination half-life that allows for once-daily dosing. This convenient dosing regimen can improve patient compliance, particularly for those requiring long-term anti-inflammatory therapy. Since its approval in 1987, tenoxicam has been widely used in many countries across Europe, Asia, and other regions, although it has not received approval for use in the United States.
Chemical Structure
Tenoxicam has the chemical formula C13H11N3O4S2 with a molar mass of 337.37 g·mol−1. The compound has a melting point between 209 to 213 °C (408 to 415 °F), at which point it decomposes. As a member of the oxicam class of NSAIDs, tenoxicam shares structural similarities with other drugs in this group such as piroxicam, meloxicam, and lornoxicam.
The oxicam class differs structurally from other NSAIDs in that they are not carboxylic acids. Instead, they feature a characteristic enolic acid structure that contributes to their pharmacological properties. Like other oxicams, tenoxicam exhibits tautomerism, meaning it can exist in different structural forms (tautomers) through the migration of a hydrogen atom. This property affects its physico-chemical characteristics in different environments.
Tenoxicam has relatively low lipophilicity and a high degree of ionization in blood (approximately 99%), which influences its distribution throughout the body and contributes to its pharmacokinetic profile. These characteristics result in slow uptake by hepatic cells and relatively poor distribution to body tissues, factors that contribute to its long half-life.
Tenoxicam-Based Medicines
Several pharmaceutical preparations containing tenoxicam are available worldwide, marketed under various brand names. While not available in the United States, tenoxicam is accessible in many other countries. Below are some of the most common tenoxicam-based medicines:
- Mobiflex – One of the most widely recognized brand names for tenoxicam, particularly in the United Kingdom
- Tilatil – Available in several international markets
- Tilcitin – Another international brand name for tenoxicam preparations
- Alganex – Used in various countries for tenoxicam formulations
- Tenoxicam Chemidex Pharma – Available in the United Kingdom
- Tenoxicam (AA Pharma) – Previously available in Canada, now listed as “dormant” status
- Tenoxicam (generic) – Marketed by various manufacturers globally
- Tenoxicam (Waymade Plc) – Available in the United Kingdom
These medications are predominantly available as 20 mg oral tablets, with the standard dosage being once daily.
Mechanism of Action
Tenoxicam, like other NSAIDs, primarily works by inhibiting the cyclooxygenase (COX) enzymes responsible for prostaglandin synthesis. Prostaglandins are lipid compounds that promote inflammation, pain, and fever in the body. By blocking these enzymes, tenoxicam reduces the production of prostaglandins at sites of inflammation, thereby alleviating the symptoms associated with various inflammatory conditions.
More specifically, tenoxicam is an unselective inhibitor of both COX-1 and COX-2 enzymes. While COX-2 is primarily responsible for the production of inflammatory prostaglandins, COX-1 is involved in maintaining the protective lining of the stomach and regulating normal cellular processes. This non-selective inhibition explains both the therapeutic effects and some of the side effects of tenoxicam, particularly those affecting the gastrointestinal system.
In addition to prostaglandin synthesis inhibition, in vitro studies suggest that tenoxicam may also act as a scavenger for active oxygen at the site of inflammation. This additional mechanism could contribute to its anti-inflammatory efficacy. Research has also indicated that tenoxicam may have protective effects against ischemia-induced damage in certain tissues, though the clinical significance of this finding requires further investigation.
Pharmacokinetics
Tenoxicam exhibits distinctive pharmacokinetic properties that contribute to its clinical utility and once-daily dosing regimen. It is completely absorbed following oral administration, with high bioavailability. Although food intake can delay absorption, it does not affect the overall bioavailability of the drug.
The drug is extensively bound to plasma proteins, with approximately 99% of tenoxicam being protein-bound in human plasma. This high degree of protein binding, combined with its low lipophilicity and high level of ionization in blood, results in limited distribution to body tissues. Consequently, tenoxicam has a relatively small apparent volume of distribution, reported to be around 9.6L (range 7.5 to 11.5L) in healthy volunteers.
Peak plasma concentrations of approximately 2.7 mg/L are typically reached about 1.9 hours after oral administration of a standard 20 mg dose in fasted individuals. One of tenoxicam’s most distinctive characteristics is its long elimination half-life, which averages around 67 hours (range 49 to 81 hours). This extended half-life allows for once-daily dosing, enhancing patient compliance.
Tenoxicam demonstrates linear pharmacokinetics over doses ranging from 10 to 100 mg. It is metabolized almost entirely by the liver through oxidation and conjugation pathways. The primary metabolites are the 5′-hydroxy and 6-O-glucuronidated forms, which are excreted in urine and bile, respectively. Less than 1% of tenoxicam is excreted unchanged. The drug has a low total plasma clearance of approximately 0.106 L/h.
After multiple dosing, tenoxicam reaches steady-state levels within 10-20% of predicted values during the first two weeks of therapy. Importantly, the pharmacokinetic profile is not significantly influenced by age, sex, or the presence of rheumatic disease, making dosage adjustments unnecessary in these populations.
Therapeutic Uses
Tenoxicam is approved for several inflammatory conditions, with its efficacy well-established across various indications. Below is a table outlining its primary therapeutic uses:
| Condition | Description | Dosage |
|---|---|---|
| Rheumatoid Arthritis | Chronic inflammatory autoimmune disorder affecting joints | 20 mg once daily |
| Osteoarthritis | Degenerative joint disease caused by cartilage breakdown | 20 mg once daily |
| Ankylosing Spondylitis | Inflammatory arthritis affecting the spine and large joints | 20 mg once daily |
| Tendinitis | Inflammation of a tendon, often due to overuse | 20 mg once daily |
| Bursitis | Inflammation of the fluid-filled sacs (bursae) that cushion joints | 20 mg once daily |
| Periarthritis | Inflammation of tissues surrounding joints (shoulders/hips) | 20 mg once daily |
In some patients, a lower dose of 10 mg (half tablet) daily may be sufficient for symptom management. Higher doses are generally not recommended as they typically do not provide significantly greater therapeutic benefits but may increase the risk of adverse events. The full therapeutic effect for certain types of arthritis may take up to two weeks to become apparent.
Side Effects
Tenoxicam, like other NSAIDs, is associated with various side effects that range from common and mild to rare but potentially serious. Gastrointestinal adverse effects are particularly common with tenoxicam use, affecting between 10.4% and 23.0% of patients. These include dyspepsia (0.1-9.7%), nausea (2.0-6.7%), constipation (0.5-2.9%), abdominal pain (0.7-3.3%), and diarrhea (0.5-2.3%).
More serious gastrointestinal complications such as peptic ulceration and gastrointestinal bleeding (including hematemesis and melena) occur in approximately 0.1-0.6% of patients taking tenoxicam at doses of 10-40 mg daily. Other gastrointestinal side effects include vomiting, ulcerative stomatitis, gastritis, and esophagitis.
Cardiovascular effects may also occur, including increased blood pressure and, rarely, palpitations. Nervous system side effects include headache, dizziness, and rarely, sleep disturbances and vertigo. Hypersensitivity reactions such as rash, pruritus, erythema, and urticaria can occur in some patients.
Rare but serious dermatological reactions have been reported with oxicam-class NSAIDs, including tenoxicam. These include Stevens-Johnson syndrome and toxic epidermal necrolysis, which are considered very rare but potentially life-threatening. Due to this association, oxicams, including tenoxicam, are not regularly prescribed in some clinical settings.
Other potential adverse effects include edema (uncommon), fatigue (uncommon), and various rare effects such as cardiac disorders and nervous system disorders. As with other NSAIDs, there is also a risk of renal effects, particularly in elderly patients or those with pre-existing kidney conditions.
Drug Interactions
Tenoxicam has numerous documented drug interactions that can affect its efficacy or increase the risk of adverse effects. Clinicians must be aware of these interactions to ensure safe and effective therapy.
One of the most significant concerns is the potential for increased risk of side effects when tenoxicam is combined with other NSAIDs. Concurrent use with medications like diclofenac, ibuprofen, or naproxen should be avoided as this can increase the risk of adverse effects, particularly gastrointestinal complications. Similarly, combining tenoxicam with aspirin or other salicylates may increase the risk of side effects.
Tenoxicam can potentially reduce the effectiveness of certain antihypertensive medications. It may decrease the antihypertensive activities of beta-blockers (such as metoprolol), ACE inhibitors (like fosinopril), and ARBs (such as olmesartan). This interaction is particularly important as it forms part of the “triple whammy” effect when NSAIDs are used with ACE inhibitors/ARBs and diuretics, which can be harmful to the kidneys.
The effectiveness of diuretics, including furosemide, metolazone, and hydrochlorothiazide, can be decreased when used concurrently with tenoxicam. This can affect blood pressure control and fluid balance.
Tenoxicam may increase the serum concentration of methotrexate, potentially enhancing its toxicity. It may also increase the nephrotoxic activities of medications like cyclosporine and tacrolimus. Additionally, the risk of bleeding can be increased when tenoxicam is combined with anticoagulants such as warfarin, apixaban, rivaroxaban, or dabigatran.
The metabolism of tenoxicam can be affected by various medications. Drugs like fluconazole, omeprazole, and gemfibrozil can decrease its metabolism, potentially increasing tenoxicam levels and side effects. Conversely, medications such as rifampicin, phenytoin, and barbiturates may increase tenoxicam metabolism, potentially reducing its therapeutic effect.
Safety Considerations
Several important safety considerations must be taken into account when prescribing tenoxicam. The medication is contraindicated in patients with active peptic ulcer or active inflammatory diseases of the gastrointestinal tract due to the risk of exacerbating these conditions. It should also not be used in patients who have shown hypersensitivity to tenoxicam or who experience acute asthmatic attacks, urticaria, rhinitis, or other allergic reactions when taking aspirin or other NSAIDs.
Special caution is needed in elderly patients, particularly before anesthesia or surgery, and in patients at risk of renal failure or increased bleeding. Tenoxicam requires careful consideration in patients with high blood pressure, heart or kidney problems, or a history of asthma. Patients who smoke may also face additional risks when taking this medication.
Tenoxicam is contraindicated during the third trimester of pregnancy due to risks of premature closure of the ductus arteriosus and prolonged parturition. Caution is also recommended during the first and second trimesters, particularly from the middle to end of the second trimester (approximately 20 weeks), due to possible fetal renal dysfunction leading to oligohydramnios. Pregnant women should always consult their healthcare provider before using any NSAID, including tenoxicam.
The “triple whammy” effect, which occurs when NSAIDs like tenoxicam are combined with ACE inhibitors/ARBs and diuretics, can be harmful to the kidneys and should be avoided. Examples of ACE inhibitors include captopril, cilazapril, and enalapril, while ARBs include candesartan, irbesartan, and losartan. Diuretics include furosemide, bumetanide, and spironolactone.
Safety in pediatric patients has not been established, and Health Canada has not authorized an indication for pediatric use. Additionally, tenoxicam can be harmful when taken while dehydrated or after being sick with diarrhea or vomiting.
Regulatory Status
Tenoxicam has a varied regulatory status across different regions worldwide. It was patented in 1974 by Roche and received approval for medical use in 1987. While tenoxicam is available as a prescription medication in many countries, including the United Kingdom and various nations across Europe, Asia, and elsewhere, it has never received approval for use in the United States.
In Canada, tenoxicam was previously available under DIN 02230661, marketed by AA Pharma Inc. However, as of September 1, 2022, its status has been changed to “Dormant,” indicating it is no longer being actively marketed. The standard prescription strength was 20 mg tablets.
The European Medicines Agency (EMA) has reviewed tenoxicam as part of its pharmacovigilance activities, and the medication remains available through various national authorizations across European countries. Different brand names and generic versions are marketed by various pharmaceutical companies in these regions.
Regulatory bodies generally recognize tenoxicam as an effective treatment for inflammatory conditions while acknowledging its potential adverse effects. Prescribing information typically includes warnings about gastrointestinal risks, cardiovascular effects, and potential for severe cutaneous adverse reactions. These regulatory considerations reflect the balance between the therapeutic benefits of tenoxicam and its potential risks, highlighting the importance of appropriate patient selection and monitoring during treatment.
Conclusion
Tenoxicam represents an important treatment option in the NSAID class, particularly within the oxicam subgroup. Its once-daily dosing regimen, afforded by its long half-life, provides a convenient option for patients requiring ongoing anti-inflammatory therapy. While effective for various inflammatory conditions including rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis, tenoxicam must be prescribed with careful consideration of its potential side effects and numerous drug interactions.
The medication’s pharmacokinetic profile, featuring complete oral absorption, high protein binding, and hepatic metabolism, contributes to its clinical utility. However, safety considerations-particularly for elderly patients, those with cardiovascular or renal conditions, and pregnant women-necessitate careful patient selection and monitoring.
Despite not being available in the United States, tenoxicam continues to be prescribed in many countries worldwide, playing a valuable role in managing inflammatory conditions when used appropriately. As with all NSAIDs, the benefits of tenoxicam therapy must be weighed against potential risks, with healthcare providers tailoring treatment approaches to individual patient needs and characteristics.
