I'm taking olfen for sometimes now. Any long term side effect.?

Side effects. Olfen is the brand name of a pain-killer/anti-inflammatory called diclofenac sodium. It should be avoided in people with high blood pressure and heart diseases, though it is not totally prohibited in these conditions. Its side effects include: nausea, tummy ache, headache, retention of water in the body (oedema), dizziness, skin rash etc. Long term use can increase your risk of ulcers and hyperten.