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Hydrochlorothiazide Side Effects: Skin Cancer and More!

Few health professionals think hydrochlorothiazide side effects are serious. But a Danish study links HCTZ with squamous cell skin cancer.
Hydrochlorothiazide Side Effects: Skin Cancer and More!
Illustration of doctor’s desktop with different pills, capsules, statoscope, syringe, yellow folder with label ‘Skin Cancer’

You have been advised by the American Heart Association and the American College of Cardiology that if you have systolic blood pressure of 130 or higher and/or diastolic blood pressure of 80 or higher that you have hypertension. That means at least half of all adults in the United States now have high blood pressure. The chances are good that many of them will be prescribed thiazide diuretics as first line therapy. But what are hydrochlorothiazide side effects? Is skin cancer one of them?

Hydrochlorothiazide (HCT or HCTZ) and Blood Pressure:

One of the most popular blood pressure pills in the world has been linked to skin cancer. More than 20 million Americans take hydrochlorothiazide or HCTZ every day. It is found in dozens of combination blood pressure pills and has been perceived as an extremely safe choice for controlling hypertension.

In addition, thiazide diuretics are prescribed to lower the risk of recurrent kidney stones. Find that hard to believe? Here is a link to a recent article:

Can Blood Pressure Pills Prevent Kidney Stones?
Certain blood pressure pills known as thiazide diuretics can help prevent kidney stones. Drinking plenty of water is also critical!

There are, however, a number of hydrochlorothiazide side effects. One that may not be mentioned very often is an increased sensitivity to sunlight. It might be perceived by health professionals as a minor adverse reaction. But this reader suggests otherwise:

Hydrochlorothiazide Side Effects: Skin Cancer?

Q. For about two decades, I took the diuretic hydrochlorothiazide (HCTZ) to prevent recurring kidney stones. I’d had five years in a row dealing with these stones. Changing my diet and increasing my fluid intake didn’t help but the drug did.

A Danish study came out noting an increased skin cancer risk from HCTZ. My basal cell carcinoma and squamous cell carcinoma lesions were removed eight years into taking this drug.

The melanoma lesion on my scalp appeared the following year. By then, it had spread to my lungs and bones. When the study came out, my oncologist discontinued the HCTZ. This was many years into my cancer journey, though. Luckily, I am in my second remission with immunotherapy every three weeks for the last five years.

The Danish Study:

The Danish study you mention does indeed link thiazide diuretics with squamous cell carcinoma (Journal of the American Academy of Dermatology, April, 2018). This type of skin cancer is linked to excessive sun exposure. HCTZ sensitizes the skin to ultraviolet radiation from the sun. By making the skin more vulnerable to sunlight, skin damage and sunburn is more likely. 

The study included 80,000 Danish citizens with non-melanoma skin cancer. Those who took the highest dose of hydrochlorothiazide for the most years were seven times more likely to develop squamous cell carcinoma than people who took no HCTZ. The scientists looked at other blood pressure medications and did not find any similar associations.

Squamous Cell Carcinoma:

When most people think about common cancers they immediately imagine breast cancer, lung cancer, prostate cancer and colon and rectum cancer. According to the American Cancer Association, the projections are that in 2017 there will be:

253,000 cases of breast cancer
222,000 cases of lung cancer
161,000 cases of prostate cancer
135,000 cases of colorectal cancer

It comes as a total shock to learn that the American Academy of Dermatology estimates that:

“Squamous cell carcinoma (SCC) is a common skin cancer in humans. About 700,000 new cases of this skin cancer are diagnosed in the United States each year.”

Most people do not worry much about skin cancer unless there is a diagnosis of melanoma. They assume that squamous cell carcinoma is not that big a deal. Although squamous cell carcinoma (SCC) is often successfully treated with surgery, it can occasionally be lethal. An article in JAMA Dermatology (May, 2013) noted:

“Cutaneous squamous cell carcinoma [CSCC] carries a low but significant risk of metastasis and death. In this study, patients with CSCC had a 3.7% risk of metastasis and 2.1% risk of disease-specific death.”

Hydrochlorothiazide Side Effects and Squamous Cell Carcinoma:

The Danish researchers have been concerned about the link between hydrochlorothiazide and squamous cell carcinoma for some time. They reported in the Journal of Internal Medicine (Oct. 2017) that:

“Hydrochlorothiazide use is strongly associated with an increased risk of lip cancer.”

They described it as a “clear dose-response effect.” In other words, the greater the exposure to the drug the more serious the risk.

In their latest publication, they note:

“Recently, we reported a strong association between use of the diuretic hydrochlorothiazide (HCTZ) and squamous cell carcinoma (SCC) of the lip. We found a clear dose-response pattern, with an estimated 7-fold increased risk of SCC lip cancer with cumulative use of ≥100,000 mg HCTZ. Our findings were in line with the results of previous studies from the United States (US) and the recent classification of HCTZ as ‘possibly carcinogenic to humans’ (Group 2B) by the International Agency for Research on Cancer (IARC). As HCTZ is among the most widely used drugs in the US and western Europe, a carcinogenic effect of HCTZ would have a considerable impact on public health.”

The authors conclude:

“In conclusion, given the considerable use of HCTZ worldwide and the morbidity associated with NMSC [non-melanoma skin cancer], a causal association between HCTZ use and NMSC risk would have significant public health implications. The use of HCTZ should be carefully considered, as several other antihypertensive agents with similar indications and efficiency are available, but without known associations with skin cancer.”

Thiazide Diuretics and Melanoma?

Any link between thiazide diuretics and melanoma is controversial. A review of the medical literature offers this conclusion (Journal of Clinical Medicine Research, April, 2019):

“In this meta-analysis of observational studies, we found significant association between the use of thiazide diuretics and the risk of SCC [squamous cell carcinoma]. There were marginally significant associations between thiazide use and the risk of BCC [basal cell carcinoma] and MM [malignant melanoma].”

A connection between thiazide diuretics and melanoma is uncertain. A study from South Korea has even suggested that HCTZ might “have a chemopreventive effect against the development of melanoma (Korean Journal of Internal Medicine, July, 2020).  

That said, people taking this diuretic should avoid direct sun exposure and ask a dermatologist to check their skin on a regular basis.

The People’s Pharmacy Perspective:

Hydrochlorothiazide is considered very safe by most physicians. This diuretic is often the first line treatment for high blood pressure. What is especially concerning is that many patients don’t even realize they are taking HCTZ. That’s because it is frequently added to another drug such as an ACE inhibitor a beta blocker or an ARB. For a list of drugs containing hydrochlorothiazide, please visit this link.

Other Hydrochlorothiazide Side Effects:

There are a surprising number of hydrochlorothiazide side effects that often go unmentioned. They include electrolyte imbalances, elevated blood sugar, raised uric acid levels, muscle cramps, irregular heart rhythms, dizziness, elevated cholesterol levels, and dry eyes.

To learn more about hydrochlorothiazide side effects, visit this article:

Hydrochlorothiazide (HCTZ) Side Effects, Complications and Gout!

Share your own story about hydrochlorothiazide side effects in the comment section below. If you have done well with this drug we would like to hear from you as well. If you think this information is helpful, please share it with friends and family by clicking on the email icon at the top of this page or sending it via Facebook or Twitter.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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