Thiazide diuretics: adverse effects and teaching

A thiazide diuretic lowers blood pressure by making the kidney excrete sodium and water and, over the longer term, by relaxing the resistance vessels, so its predictable harms are the losses and the metabolic shifts that follow from that action and the nurse anticipates, watches for and teaches every one of them — volume depletion and a fall in pressure on standing, sharpest where the patient is also vomiting, has diarrhea, is sweating heavily or is taking other pressure-lowering drugs, so the patient is taught to rise slowly and to seek advice rather than keep taking the tablet through an illness that is draining fluid; a loss of potassium that shows itself as muscle weakness, cramps, fatigue, constipation and an irregular pulse and is most dangerous in the patient also taking digoxin, whose toxicity a low potassium unmasks, so the potassium is checked before the drug starts and early in treatment and kept up by the potassium-rich foods or the supplement or potassium-sparing partner that is prescribed alongside, never by a supplement the patient or nurse adds unasked; a loss of sodium and magnesium that presents in the older patient as confusion, lethargy, nausea and weakness rather than as thirst; a rise in uric acid that can provoke gout, in glucose that can unsettle a diabetic patient's control, in calcium and in lipids, each read as the drug's doing rather than as a new disease; and photosensitivity of the skin — while the patient is taught to take the tablet in the morning so that the diuresis does not cost them their sleep, that the drug goes on lowering the pressure after the early increase in urine has worn off and is not stopped or judged useless on that account, that non-steroidal anti-inflammatories blunt it and that lithium levels rise on it, and that it loses its effect as kidney function falls so the team is told of any decline.