A couple years ago I flew directly from the Amazon to Cusco and in the process got hit with altitude sickness pretty badly. Dry cough, throbbing headache, the whole bit. While coca tea helps, I would definitely suggest buying the leaves and putting them directly in your mouth like chewing tobacco. I had been suffering for a day and a half when I came across a vendor selling coca leaves. Within a minute of putting them in my mouth I felt better. Far more effective than the tylenol I had been taking.