Use protection from melee whilst fighting these. They are known to hit fairly hard without it, even at high levels. Bring prayer potions, stat enhancing potions (supers, extremes, overloads, prayers) to help you fight these faster.
Contrary to popular belief these do NOT drop dragon full helms.
Turn on protect melee and finish it off. Try to have a prayer pot or two, just in case you take a while killing it. They are also weak against magic attacks.
He looks a tad upset.
Dragon med helm
Big bones (10) (100%), Rune mace, Adamant mace, Adamant knife (20-30), Rune battleaxe, Potion mixes, Raw sharks, Rune scimitar, Rune arrow (10), Bronze hasta, Iron hasta, Steel hasta, Death rune (7-8), Mithril grapple (2), Silver bar (2), Herb seeds, Shark (3), Grimy herbs, Silver bolts (5), noted Adamant bar (1), Rune bolts (10), Ancient page