Hypokalemia is a characteristic feature of toxicity with:-

Mechanism of toxicity of Barium: Hypokalaemia and neuromuscular blockade: Rapid onset of marked hypokalaemia, characteristic of barium intoxication is due to sequestering of potassium by muscle cells. Barium clogs exit channel for potassium ions in skeletal muscle cells. Barium stimulates striated, smooth and cardiac muscle resulting in violent peristalsis, aerial hypeension and arrhythmias.