Well, the weather conditions can be wuite variable. We have to travel through a rainforest which at the very least will be damp and possibly very rainy. Then up on to the moorland and final the high mountains. The moorland could be very sunny with high levels of solar radiation (35-40C daytime highs).
I've seen video clips on youTube where people had rain and snow for most of their journey. We had to pack with these extremes in mind.
The porters have a 15kg limit on the kit bags along with whatever you want to carry. So our packing included base layers, thin mid-layer fleeces, thick fleeces, waterproof outers (coat and trousers) and then for the evenings and summit night a thick down jacket.
Well on the mediciation front, there is the usual combination of Malaria tablets, water purification (on top of yellow fever, H1N1, tetanus, polio, Hepatitus A and a few other injections).
But then for alititude quite a few people take a drug called Diamox. It basically aids acclimatization by re-acidifying the blood, helping to increase oxygen uptake and giving you better sleep at altitude. The problem is it has certain side effects.... it acts as a strong diuretic and also can cause tingling in the body... that's okay but that might mask the onset of a stroke.
After a lot of careful consideration we decided not to take it, it's personal choice, and I know people who would never have made the summit without it, but we wanted to see if we could do it without drugs.