What does "inefficacious" mean?

Inefficacious: Not efficacious; not having power to produce the effect desired; inadequate; incompetent; inefficient; impotent. Boyle. The authority of Parliament must become inefficacious . . . to restrain the growth of disorders. Burke. Note: Ineffectual, says Johnson, rather denotes an actual failure, and inefficacious and habitual impotence to any effect. But the distinction is not always observed, nor can it be; for we can not always know whether means are inefficacious till experiment has proved them ineffectual. Inefficacious is therefore sometimes synonymous with ineffectual.