Top 5 Thiazide Diuretic Adverse Effects

Thiazide diuretics are commonly are one of the most commonly used classes of antihypertensive agents. They carry many adverse effects. Some can be a nuisance while others can be more serious. In this blog post, I’ll run down the most common thiazide diuretic adverse effects to be aware of.

Urinary Frequency

I would classify urinary frequency as the most common adverse effect. Thiazides primarily work by increasing the amount of fluid in the bladder. This is going to make the patient go to the bathroom more frequently. One of the biggest mistakes I’ve seen made with regard to timing the dose is giving a thiazide diuretic too late in the day and causing insomnia due to urinary frequency at night.

Electrolyte Deficiency

Hyponatremia, hypokalemia, and hypomagnesimia are all potential electrolyte complications with the use of thiazide diuretics. Electrolyte monitoring is going to be important when one of these agents is prescribed. Hyponatremia risk can go up significantly when using thiazide diuretics in combination with other agents that can cause SIADH. Knowing some of those medications (i.e. carbamazepine, SSRIs, etc.) that can cause SIADH is a frequently asked board exam question that you should know!

Sexual Impairment

Sexual impairment or sexual dysfunction is a possible adverse effect of thiazide diuretics. If this is a concern, we do have antihypertensive that may have a lower risk of this occurring. CCBs, ACE inhibitors, or ARBs tend to have a lower risk and would be preferred in a patient where this is an issue.

Hyperuricemia and Hyperglycemia

Gout flares can be more common with the use of thiazide diuretics This is because they may increase uric acid levels. Pay attention to a new diagnosis of gout or the need for increasing gout medications like allopurinol if a thiazide diuretic is added to a patient’s regimen. I don’t worry quite as much about hyperglycemia, but it should be monitored. If you notice that blood sugars substantially rise following the initiation of a thiazide, a risk versus benefit assessment should be done. I have previously shared a case study on this that may be helpful for you to review.

Hypercalcemia

While electrolyte deficiencies are an important aspect of thiazide diuretic adverse effects, thiazides are also associated with hypercalcemia. Typically this can be easily identified as we are usually already checking labs anyway with the risk for hypokalemia. I tend to worry a little more when patients have other risk factors for hypercalcemia such as excessive intake of calcium or vitamin D, renal disease, or certain types of cancer.

What other adverse effects have you seen from thiazide diuretics?

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