Martin Pleasance Tissue Salts Mag Phos Muscle Relax Cream 75g. Mag Phos is the anti-spasmodic, tissue salt. It is the remedy which relieves cramps and aches and supplements the action of Kali Phos. Mag Phos is quick to relieve pain, especially cramping, shooting, darting or spasmodic pain. It relieves muscular twitching, cramps, hiccups, convulsive fits of coughing and those sudden, sharp twinges of pain that are so distressing.