Descent is the most effective cure for AMS. The chances are that on your trek you will see at least one poor sod being wheeled down Kili, surrounded by porters and strapped to the strange unicycle-cum-stretcher device that KINAPA uses for evacuating the sick and suffering from the mountain.
But in some severe cases descent is not enough. Diamox is also usually given, though again, if the victim has been suffering for a while or Diamox is not available, some other treatment may be used such as:
Some of the upmarket trek operators may carry a gamow bag with them. This is a man-sized plastic bag into which the victim is enclosed. The bag is then zipped up and inflated. As it is inflated, the pressure felt by the sufferer inside the bag is increased, thus mimicking the atmospheric conditions present at a lower altitude.
The disadvantage with this method is that of inconvenience. The cumbersome bag has to be dragged up the mountain and, worst of all, in order to work effectively once the patient is inside, the bag must be kept at a constant pressure. This means that somebody must pump up the bag every two or three minutes. This is tricky when at least two other people are trying to manoeuvre the body and bag down the slopes.
Giving the victim extra oxygen from a bottle or canister does not immediately reverse all the symptoms, though in conjunction with rapid descent it can be most effective.