These weapons were widely outlawed because of their destructive nature towards subspace yet the Son'a and other races 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.
Starships could not escape the phenomenon by engaging their warp engines as the tear would be dragged along with the fleeing ship, matching its course and speed. When the ship would drop back to impulse the distance between the tear and the ship would remain unchanged, only a vastly superior portion of space would be affected.
The only know 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 Klingon ship resulted in the destruction of the Romulan planet Algeron III, leaving behind only the Algeron Effect. In 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)
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 novel: The Dominion: Olympus Descending)