Since generalized hyperhidrosis is usually secondary to an underlying illness or a side effect of a medication, the first approach to providing relief from the excessive sweating is to investigate the cause. Underlying conditions should then be treated appropriately and relevant medications should be adjusted, if possible, to relieve the sweating symptoms. (see Causes of Secondary Hyperhidrosis).
If symptoms persist during or after treatment of the primary condition and/or medication adjustments, consideration can be given to using a systemic medication to reduce sweating. Recently, the International Hyperhidrosis Society and two of its physician leaders conducted an in-depth webinar all about the use of oral medications to treat hyperhidrosis. You can "watch the full video here." Keep in mind that it will be important to ascertain whether a specific agent is contraindicated in the primary illness and does not interact with drugs used to treat that illness. In the rare instance in which there is no underlying cause found for generalized hyperhidrosis, consideration must be given to treating the most involved areas as one would in focal hyperhidrosis.
If symptoms seem to be worse in anxiety-provoking situations (such as during public speaking), expectant use of a systemic medication may be useful.[  Propranolol may be particularly useful in this circumstance. Clonidine can be useful for the treatment of secondary hyperhidrosis due to antianxiety or antidepressant medications.