Hydrochlorothiazide is a widely prescribed diuretic, often called a “water pill,” used to manage high blood pressure and fluid retention. By helping the kidneys remove excess salt and water, it effectively lowers blood pressure and reduces swelling. While a staple in cardiovascular medicine, research has identified a connection between its long-term use and an increased risk for specific types of skin cancer.
The Scientific Connection Between Hydrochlorothiazide and Skin
The link between hydrochlorothiazide and skin cancer is rooted in its photosensitizing property. A photosensitizing agent increases the skin’s sensitivity to ultraviolet (UV) radiation from the sun or artificial sources like tanning beds. When a person taking this medication is exposed to UV light, their skin may absorb more harmful energy than it normally would, increasing the potential for cellular damage that can lead to skin cancer.
This association is not uniform across all types of skin cancer, with research showing the strongest connection to non-melanoma skin cancers. The risk is most pronounced for squamous cell carcinoma (SCC), a cancer that arises in the outer layers of the skin. A lesser association has been observed with basal cell carcinoma (BCC), the most common form of skin cancer.
The risk is not immediate but cumulative, building over time with continued use. Both the total dosage and the duration of treatment play a part in elevating this risk. Someone taking a higher dose for many years would have a more significant increase in their risk profile compared to a person on a lower dose for a shorter period.
Understanding the Level of Risk
Quantifying the risk requires understanding the difference between relative and absolute risk. Some studies report that the relative risk of developing squamous cell carcinoma could be several times higher for long-term users compared to those not taking the drug. For instance, Danish studies suggested a 7.7-fold increase in SCC risk and a 1.5-fold increase for BCC with prolonged use.
It is important to place these figures in context. An FDA analysis noted that the increased risk for SCC translated to approximately one additional case per 16,000 patients per year. While a “seven-fold” increase sounds substantial, the absolute risk—an individual’s actual chance of developing the cancer—may still be quite small.
Health Canada’s review concluded that prolonged use of three years or more could be associated with a risk of non-melanoma skin cancer at least four times higher than for non-users. An individual’s overall risk is also influenced by other factors like age and lifetime sun exposure.
Patient Guidance and Protective Measures
The most important guidance for any patient is to not stop taking hydrochlorothiazide without first consulting their doctor. High blood pressure is a serious condition that increases the risk of heart attack, stroke, and kidney disease. The benefits of controlling blood pressure are well-established and for most patients will outweigh the potential increase in skin cancer risk.
Adopting rigorous sun protection habits is a primary defensive strategy.
- Apply a broad-spectrum sunscreen with an SPF of 30 or higher to all exposed skin daily.
- Reapply sunscreen regularly, especially after swimming or sweating.
- Wear protective clothing that covers the arms and legs.
- Use a wide-brimmed hat to shield the face and neck, and UV-blocking sunglasses.
Regular skin surveillance is also advised. Patients should perform monthly skin self-exams, looking for any new growths or changes in existing moles or spots. Any suspicious lesion—such as a spot that grows, bleeds, or changes in appearance—should be promptly reported to a healthcare professional. Annual professional skin examinations by a dermatologist are also a valuable part of a screening strategy for early detection.
Balancing Treatment Benefits and Risks
The decision to continue, modify, or change treatment is a process of shared decision-making between a patient and their physician. Hydrochlorothiazide remains an effective medication for managing hypertension and other cardiovascular conditions. For many individuals, its proven ability to prevent major cardiovascular events is a benefit that justifies its continued use, even with the acknowledged skin cancer risk.
During a consultation, a doctor can help weigh the medication’s benefits against the individual’s specific dermatological risk profile. This includes considering factors like personal or family history of skin cancer, skin type, and typical levels of sun exposure. This personalized assessment allows for a more nuanced understanding of the risk-benefit balance.
Discussing potential alternatives is a reasonable part of this conversation. Depending on the patient’s overall health profile and needs, other classes of antihypertensive medications that do not have photosensitizing properties may be an option. The goal is to find a treatment plan that effectively manages the patient’s primary health condition while minimizing potential side effects.