I normally take magnesium citrate powder as part of a home-made electrolyte drink. If you do this, i.e. dilute it in liquid, it's absolutely fine. The other day I hadn't had my drink, but I was a bit constipated, so near bedtime I just grabbed the magnesium citrate and took half a teaspoonful of it. Neat. Straight off the spoon. Do not try this at home, folks. It burnt like hell for a few seconds, and my oesophagus has been hurting ever since. The pain while resting has been mild to non-existent, but swallowing and drinking have been mildly uncomfortable, and eating has been miserable. After two days of this it dawned on me that it was worth talking to a doctor, especially since I'm having my gallbladder out on Saturday and they'll be sticking tubes down my throat. The doctor diagnosed an inflamed/irritated oesophagus. He gave me Peptac to take four times a day, which he said should clear it up in a few days, and indeed it's starting to work. Peptac is a pink liquid, ominously gloopy, which tastes like a combination of bicarbonate of soda, aniseed and soap. You definitely don't want to go there.