Medication Information: Diclofenac

Mechanism Of Action

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) that works by inhibiting cyclooxygenase (COX-1 and COX-2) enzymes. This inhibition decreases the synthesis of prostaglandins, which are chemical mediators responsible for inducing inflammation, pain, and fever. The reduction in prostaglandins results in diminished inflammation and pain relief.

Pharmacokinetics Profile

Diclofenac is absorbed rapidly after oral administration, with peak plasma concentrations reached in about 2 hours. The drug is extensively metabolized in the liver via CYP2C9 enzyme, forming active and inactive metabolites. The elimination half-life is approximately 1-2 hours, and it is excreted mainly in the urine and bile.

Available Formulations

Diclofenac is available in multiple formulations, including oral tablets, extended-release tablets, topical gels, and solutions. Each formulation is designed to provide varying durations of action and specific delivery routes to maximize therapeutic benefit while minimizing adverse effects.

Indications For Use

Diclofenac is indicated for the management of arthritis, such as osteoarthritis and rheumatoid arthritis. It is also prescribed for acute pain conditions, such as tendinitis, bursitis, and dysmenorrhea. Additionally, topical formulations are useful for localized pain associated with strains, sprains, and soft tissue injuries.

Dosage Recommendations

Standard dosage for diclofenac oral tablets typically ranges from 50 mg to 75 mg taken two to three times a day. Extended-release tablets are usually taken once daily, ranging from 100 mg to 200 mg. Topical gels and patches are applied directly to the affected area, generally three to four times a day.

Common Side Effects

Patients commonly experience gastrointestinal issues such as nausea, abdominal pain, and dyspepsia. Other frequent side effects include headache, dizziness, and pruritus. Topical formulations may cause localized skin reactions like redness and itching.

Drug Interactions

Diclofenac can interact with other medications including anticoagulants, increasing bleeding risk, and antihypertensive drugs, reducing their efficacy. Concurrent use of other NSAIDs or corticosteroids can augment gastrointestinal irritation and bleeding risk. Caution is advised when used with other hepatotoxic medications.

Contradictions and Cautions

Diclofenac is contraindicated in patients with a known hypersensitivity to the drug, those with peptic ulcer disease, and individuals with severe hepatic or renal impairment. Caution is advised in patients with cardiovascular disease due to an increased risk of myocardial infarction and stroke with chronic use.

Monitoring Parameters

Frequent monitoring of liver function tests and renal function are recommended for patients on long-term diclofenac therapy. Regular assessments of cardiovascular status and gastrointestinal integrity should also be performed. Patients should be evaluated for any signs of adverse reactions or drug interactions.

Special Population Considerations

In elderly patients, dosage adjustments may be necessary due to an increased risk of adverse effects. In pregnant women, diclofenac should be avoided, especially in the third trimester, due to risk of premature closure of the ductus arteriosus. For breastfeeding mothers, the safety is not well established and thus should be used with caution.

Off-Label Uses

Diclofenac can be used off-label for treating acute gout attacks and in the management of chronic musculoskeletal pain. Although not first-line therapy, its anti-inflammatory properties can provide symptomatic relief in these conditions.

Patient Counseling Points

Pharmacists should advise patients to take diclofenac with food to minimize gastrointestinal discomfort. Patients should be informed about the importance of adhering to prescribed dosages and not exceeding recommended amounts. They should also be instructed to report any unusual symptoms such as weight gain, chest pain, or severe stomach pain immediately.

Storage And Handling Instructions

Diclofenac tablets should be stored at room temperature away from moisture and heat. Topical formulations should be kept in a cool, dry place and tightly sealed when not in use. It is important to keep all medication out of reach of children and pets.

Drug Disposal Guidelines

Expired or unused diclofenac should be disposed of according to proper medication disposal methods. Do not flush the medication down the toilet unless instructed to do so. Pharmacies often have take-back programs to ensure safe disposal of medications.

Clinical Trial Data

Clinical trials have demonstrated the efficacy of diclofenac in reducing pain and inflammation associated with arthritis and other musculoskeletal conditions. Studies have shown comparable efficacy between diclofenac and other NSAIDs, but with a varying side effect profile. It’s essential to review up-to-date clinical data to inform therapeutic decisions.