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Side Effects Initially, some patients may complain of epigastric pain, nausea and diarrhoea, headache and slight dizziness. These symptoms are often transient and disappear with continuation of medication. Drowsiness and tiredness occur rarely and disturbance of sensation, vision, and behaviour and hearing or convulsions have only been reported in isolated cases. There have also been isolated reports of severe skin reactions (erythema multiforme, Stevens-Jhonson syndrome, Lyell's syndrome) loss of hair and photosensitivity. In a Japanese study of Diclofenac tolerability involving over 18000 patients, the incidence of 'serious' gastrointestinal effects was 0.01%. Peptic ulcer may occur rarely, and blood dyscrasias and isolated cases of anaphylactoid reactions have been encountered. Lower gut disorders may also occur. In double blind studies there were fewer gastrointestinal complaints with diclofenac than aspirin. Similar studies have shown that diclofenac is better tolerated than indomethacin. Contraindications
Precautions Patients receiving longterm treatment with diclofenac should have periodic blood counts. Diclofenac sodium may cause increased blood concentrations of digoxin, lithium and methotrexate. Studies have demonstrated a pharmacokinetic interaction between diclofenac and salicylates when both are co-administered in anti-inflammatory doses. Dosage The dose range for the oral tablets is 75 - 200 mg daily in two or three divided doses with meals. Patients should be generally maintained on the lowest dosage of diclofenac consistent with achieving a satisfactory therapeutic response. In osteoarthritis, the recommended dosage is 100 - 150 mg/day in divided doses. In rheumatoid arthritis the recommended dose is 150 - 200 mg/day in divided doses and in ankylosing spondylitis, it is 100 - 125 mg/day, administered as 25 mg q.i.d. with an extra 25 mg dose at bedtime. In children over one year (usually juvenile chronic arthritis) the dose is 1 - 3 mg/kg per day in divided doses. Pharmacokinetics are not impaired in elderly patients and standard adult doses can be used. Drug Interactions Lithium : Diclofenac has been reported to increase plasma concentrations of lithium by impairing its renal excretion. Digoxin : Diclofenac has been reported to increase plasma concentrations of digoxin, but no clinical signs of overdosage have been encountered. Diuretics : Various non-steroidal anti-inflammatory agents are liable to inhibit the activity of diuretics and to potentiate the effects of potassium-sparing diuretics, thus making it necessary to monitor serum potassium levels. Methotrexate : Caution should be exercised if diclofenac and methotrexate are administered within 24 hours of each other since NSAIDs may increase methotrexate plasma levels, resulting in increased toxicity. Food has been shown to produce prolonged and variable delays in reaching maximum plasma concentrations of Diclofenac. However, chronic dose studies in which the unchanged drug and its major metabolites were measured have shown that absorption is unaffected by food. Overdosage Due to the paucity of information at present on overdosage, the symptomatology is still ill-defined; the following, however, may serve as a guide to what might be expected : dizziness, headache, myoclonic encephalopathy, impairment of consciousness, nausea, vomiting, pain in the upper abdomen, gastrointestinal haemorrhage with subsequent haematemesis or melaena, ulceration of the stomach or intestine, perforation in patients with peptic or duodenal ulcers, hepatopathy, jaundice, oliguria or anuria, increased serum transaminases and/or bilirubin. Treatment is by removal or inactivation of the drug by inducing vomiting or washing out the stomach and giving activated charcoal. In severe manifestations of overdose, haemodialysis or haemoperfusion may have to be considered.
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