Diclofenac Sodium
Pronunciation
Diclofenac sodium 100mg
Diclofenac sodium 25mg
| Generic Name 藥名 | HA Code 藥物代碼 | Classification藥物分類 |
|---|---|---|
| Diclofenac Potassium Tablet 50mg | P1S1S3 |
Mechanism of Action
Non-opioid Analgesic (NSAID) Anti-inflammatory agent, Nonselective COX inhibitor, inhibits COX-1 and COX-2 with relative equipotency
Dosage
Usual oral dose for painful conditions:
Oral: 25 to 50 mg every 6 to 8 hours to a maximum of 150 mg daily.
Deep intramuscular: 75 mg once daily, if required in severe conditions, 75 mg twice daily.
Bolus intravenous: 75 mg may be given over 30 to 120 minutes. The dose may be repeated once after 4 to 6 hours if necessary.
Diclofenac sodium 0.1% eye drops is used in various situations:
- For the prevention of intra-operative miosis during cataract surgery. It is instilled in the appropriate eye 4 times during the 2 hours before surgery
- For the treatment of postoperative inflammation after cataract surgery. It is instilled 4 times daily for up to 28 days starting 24 hours after surgery
- For pain control after accidental trauma, one drop is instilled 4 times daily for up to 2 days
- To relieve symptoms of seasonal allergic conjunctivitis, one drop is instilled 4 times daily as necessary
Topical
Diclofenac dimethylamine is used topically as a gel for the local symptomatic relief of pain and inflammation. It is applied to the affected site 3 or 4 times daily.
Administration in children
In children aged 6 months to 17 years,
for rheumatic disease, Oral: 3 to 5 mg/kg daily in 2 or 3 divided doses.
For soft-tissue disorders, oral: 0.3 to 1 mg/kg (maximum 50 mg) given 3 times daily.
Rectal: those weighing 8 to 11 kg, 12.5 mg twice daily and heavier children 1 mg/kg three times daily. Intravenous infusion or deep intramuscular injection: 0.3 to 1 mg/kg (maximum 50 mg) given 3 times daily, for up to 2 days for postoperative pain.
Regardless of route or indication, a maximum daily dose of 150 mg should not exceeded.
Side Effects
As for NSAIDs in general.
Diclofenac suppositories can cause local irritation.
Transient burning and stinging may occur with diclofenac eye drops.
Topical preparations of diclofenac such as plasters and gel may cause application site reactions.
Common side effects include heartburn, nausea, dyspepsia, diarrhoea, constipation, gastrointestinal ulceration/bleeding, headache, dizziness, rash, salt and fluid retention, and high blood pressure.
Effects on the blood: localized spontaneous bleeding, bruising and prolonged bleeding time have been reported.
It also increases the risk of heart attack, stroke, kidney failure and liver failure.
NSAID can also worsen asthma.
Cardiovascular risk
Chronic ibuprofen use has been found correlated with risk of progression to hypertension and myocardial infarction (heart attack). Both the U.S. Food and Drug Administration (FDA) and The European Medicines Agency (EMA) issues warnings of increased heart attack and stroke risk.
Skin
NSAIDs have been associated with the onset of bullous pemphigoid. It can also cause serious skin adverse events such as exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis, which can be fatal.
Pharmacokinetics
Diclofenac is rapidly absorbed when given as an oral solution, tablet or rectal suppository, or by intramuscular injection.
It is subject to first-pass metabolism so that about 50% of the drug reaches the systemic circulation in the unchanged form.
Diclofenac is also absorbed percutaneously.
At therapeutic concentrations it is more than 99% bound to plasma proteins.
Diclofenac penetrates synovial fluid where concentrations may persist even when plasma concentrations fall; small amounts are distributed into breast milk.
The terminal plasma half-life is about 1 to 2 hours.
It is excreted mainly in the urine (about 60%) but also in the bile (about 35%); less than 1% is excreted as unchanged diclofenac.
