Caffeine is commonly used as a component in pain-relieving medicines available from pharmacies without a prescription. An adjuvant is something that is added to a medicine to make it work better. This review examined whether caffeine improves the pain-relieving effects of such medicines; studies evaluated focused on several pain conditions, including headache, post-dental pain, postoperative pain following childbirth, and menstrual period pain. The review found that adding caffeine, at a dose equivalent to a mug of coffee to a standard dose of common analgesics such as paracetamol or ibuprofen increases the number of people with acute pain who will experience a good level of pain relief by 5% to 10%.