I pulled this off of best of elite fitness:
Clenbuterol comes in 20mcg tablets, although it is also available in syrup, pump and injectable form. Doses are very dependent on how well the user responds to the side effects, but somewhere in the range of 5-8 tablets per day for men and 1-4 tablets a day for women is most common. Clenbuterol loses its thermogenic effects after 6-8 weeks when body temperature drops back to normal. It's anabolic/anti-catabolic properties fade away at around the 18 day mark. Taking the long half life into consideration, the most effective way of cycling clen is 2 weeks on/ 2 weeks off for no more than 12 weeks. Ephedrine can be used in the off weeks.