These weapons were widely outlawed because of their destructive nature towards subspace, yet the Son'a and other races and cultures still used them in the 24th century. These weapons functioned by creating a tear in subspace near the target, the anomaly then moves towards the target at warp one, the speed of light.
One way to counter this weapon was the ejection of the warp core and detonating at a perfectly timed moment. This would usually occur upon the ships destruction.
In one case, the use of an isolytic subspace weapon by a Graymel ship resulted in the destruction of the Romulan planet Algeron III, leaving behind only the Algeron Effect. In the year 2311, the United Federation of Planets, Romulan Star Empire, and Klingon Empire all formally banned the creation and use of isolytic weapons during the Treaty of Algeron. The Second Khitomer Accords continued the ban. (TLE novel: Serpents Among the Ruins; TNG movie: Insurrection; ST - Typhon Pact novel: Raise the Dawn)
In December 2376, the Ascendants detonated an isolytic subspace weapon, causing a star near the Great Link's planet to go nova. The Progenitor was killed by the radiation. (DS9 - Worlds of DS9 novel: The Dominion: Olympus Descending, DS9 novel: Ascendance)