Plaquenil (hydroxychloroquine sulfate) is an antimalarial drug that's also supposed to be effective against lupus, rheumatoid arthritis and skin problems caused by the sun.
In the US, the drug regulators view it as a powerful, potentially dangerous compound, while their UK equivalent seem to take a more relaxed view.
This is probably best illustrated in the recommendations for usage by children. The UK authorities see nothing wrong in giving the drug to them provided the dose does not exceed 6.5 mg per kg of body weight a day. The 200 mg tablet is not suitable for children weighing less than 33 kg (just over five stone), they suggest.
In the US, any doctor who prescribes Plaquenil to a child could face a lawsuit. A number of fatalities have been reported among children who have taken doses as low as 0.75 g, as happened with one three year old. American parents are warned to keep the drug well out of the reach of their children.
But it isn't just parents who should be on their guard. People who suffer eye problems should be warned off the drug, and psoriasis and porphyria sufferers could find their condition worsens if they take it.
Alcoholics and people with a liver problem should also avoid the drug, as should pregnant women unless suffering from malaria, when the doctor may decide any risks could be outweighed by possible benefits.
Once on the drug, reactions can include irritability, nervousness, emotional changes, nightmares, convulsions, nerve deafness, muscle weakness, blurred vision (reversible once treatment stops), light flashes, edema, bleaching of hair, alopecia, aplastic
anemia, anorexia and nausea to name just a few!