The differences between these two drugs are primarily in the strength of the dosage, with Voltaren being the stronger of the two drugs. Aside from its topical form (a gel that is applied to the affected areas), Voltaren is available in high dosages by prescription only (25mg is over the counter). Voltaren painkillers in dosages of 50 and 75 mg are usually used for mild or moderate pain associated with the following diseases: osteoarthritis, rheumatoid arthritis, menstrual cramps. In contrast, ibuprofen is suitable for a wider range of ailments. Its over-the-counter form with a strength of 200 mg provides temporary relief for mild pain associated with: Headache, Fever, Back Pain, Mild Arthritis Pain, Toothache, Muscle Aches, Menstrual Cramps. You can buy Voltaren tablets with a potency of 25 mg and Ibuprofen with a potency of 200mg-400mg without a prescription. In higher strengths, both drugs require a prescription.