Diclofenac

Drug Reference 9 min 695

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Created On: 27/09/2019

Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID), advocated for treating mild to moderate pain and helps in symptomatic relief from signs and symptoms of osteoarthritis or rheumatoid arthritis.

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Introduction

Pharmacological Class: NSAID

Indications

Mild to moderate pain
Primary Dysmenorrhea
Osteoarthritis
Rheumatoid Arthritis
Actinic Keratosis
Ocular Inflammation
Ankylosing Spondylitis
Tendinitis & Bursitis
Sciatica
Myalgia
Acute Gout
Sprains & Strains

Pharmachologic action

Diclofenac elicits an anti-inflammatory effect due to inhibition of both leukocyte migration and the enzyme cyclooxygenase (COX-1 and COX-2), leading to the peripheral inhibition of prostaglandin, prostacyclin and thromboxane products synthesis, which is further responsible for the analgesic effects of diclofenac. It also exhibits antipyretic effects due to action on the hypothalamus, resulting in peripheral dilation, increased cutaneous blood flow, and subsequent heat dissipation.

Dosage

Adult dose for

Osteoarthritis: 75 mg orally twice a day
Ankylosing spondylitis: 25 mg orally 4 times a day
Dysmenorrhea: 50 mg orally 3 times a day
Mild to moderate pain: 50 mg orally 3 times a day
Rheumatoid arthritis: 75 mg orally twice a day

Pediatric dose for

Pain: 2- 3 mg/kg/day orally in divided doses 2-4 times daily

Note : Not recommended for children less than 18 months of age

Pharmacokinetics

Diclofenac is completely absorbed from the gastrointestinal tract and is more than 95% bound to human serum proteins, primarily to albumin. Diclofenac diffuses into and out of the synovial fluid. When taken with food the T_maxis delayed by 2 hours and a 2-fold increase in C_maxvalues. It is eliminated through metabolism and subsequent urinary and biliary excretion of the glucuronide and the sulfate conjugates of the metabolites with approximately 65% of the dose is excreted in the urine and 35% in the bile as conjugates of unchanged Diclofenac plus metabolites. The terminal half-life of unchanged Diclofenac is approximately 2 hours.

Contraindications

In patients with established:

Ischemic Heart Disease
Peripheral Arterial Disease
Cerebrovascular Disease
Congestive Heart Failure
Asthma

Drug interaction

Reduced its protein binding when administered with aspirin
Increased the toxicity of certain drugs and may affect renal prostaglandins when administered with cyclosporine
It may diminish the antihypertensive effect of Angiotensin converting enzyme inhibitors
Reduces the natriuretic effect of furosemide and thiazides in some patients
Produces an elevation of plasma lithium levels and a reduction in renal lithium clearance
Increased the risk of Gastrointestinal bleeding when administered with warfarin
It is not advisable to administer diclofenac with triamterene or methotrexate

Side effects

Common (affecting between 1 in10 to 1 in 100)

Abdominal or stomach bloating, burning, cramping, or pain
Constipation
Dizziness
Nausea and vomiting
Headache

Uncommon (affecting 1 in 100 to 1 in 1000)

Troubled breathing with exertion
Loss of appetite
Itching skin or rash
Diarrhoea
Cloudy urine

Very rare (affecting less than 1 in 10,000)

Unusual bleeding or bruising
Weight loss
Agitation
Blurred vision
Muscle twitching
Pain or discomfort in the chest, upper stomach, or throat
Puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue

Precautions

Caution should be exercised in patients with allergies to aspirin or other NSAIDs such as ibuprofen and naproxen or any other medication
It is not advised in pregnancy especially the last months of pregnancy because they may cause premature closure of the ductus arteriosus
Alcohol consumption with these drugs should be avoided
Patient who have undergone dental surgery and phenylketonuria should not take this drug

Clinical evidence

In foreign and United States, data from more than 100,000 patients were collected to provide the substantial evidence of diclofenac safety and tolerability. In United States, short term trials showed less frequency and severity of side effects of diclofenac as compared to placebo, aspirin, and other NSAIDs. In long term trials, diclofenac has been taken safely for a year or more. The final experience showed that diclofenac is one of the safest agents to its kind for the treatment of a broad range of rheumatoid conditions.¹
Administration of diclofenac potassium for menstrual pain is effective in relieving menstrual pain and restoring physical performance to levels achieved when the women were in the late-follicular (no menstruation, no pain) phase of the menstrual cycle.²
Data from available placebo-controlled clinical trials indicate that diclofenac-potassium 50 or 100mg as an immediate-release tablet is more effective than placebo and as effective as oral sumatriptan 100mg and ergotamine plus caffeine at reducing pain intensity in patients with migraine 2 hours after initial administration. Duration of pain relief is similar for the 3 drugs but onset appears to be faster with diclofenac-potassium than with oral sumatriptan or ergotamine plus caffeine.³