The government is to tighten the criteria governing the use of compulsory treatment in the Mental Health Bill.
The bill, which enters its report stage in the House of Lords next week, says people can only be detained if "appropriate treatment" is available, but removes the current requirement that their condition must be considered treatable.
A government amendment published this week specifies that the purpose of treatment must be to "alleviate, or prevent a worsening of, the disorder or one or more of its symptoms or effects".
Other amendments include allowing 16 and 17-year-olds to override the wishes of their parents if they want to refuse treatment.
A further change would allow people to be transferred from a "place of safety", often a police station, to a hospital on the assessment of a single doctor, rather than having to wait to be sectioned as at present. And patients with the capacity to decide would be able to refuse electro-convulsive therapy.
Mental Health Alliance policy lead Tim Spencer-Lane said: "We've got a few concessions, which are good and still have the report stage." He added that campaigners expected to make more progress in the Lords over some headline issues.