The typical starting dose for adults (18-64) is 0.25mg should take twice daily, and the maximum dose is 4mg. The dosages of the drug will depend on the age, weight, medical condition, and response to the treatment. In childrens, the dose amount mainly depends on the weight. Older adults should start the drug with low dosages to decrease the risk of side effects or other adverse effects. Do not increase your dose amount and take it longer than prescribed without consulting the doctor.