PhotosensitivityPhase 1NCT04654312
Study to Evaluate the Influence of Hydrochlorothiazide on Dermal Photosensitivity and DNA Stability - a Pilot Study (HCTox Study)
A Phase 1 study testing Hydrochlorothiazide in people with Photosensitivity, run by Universität des Saarlandes at 1 site in Germany.
Trial summary
The clinical trial is designed as a national, prospective, single-center, double-blind, parallel group, randomized, controlled, interventional trial to investigate whether a therapy with HCT compared with placebo can affect dermal photosensitivity and DNA stability. Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- Photosensitivity
- What is being tested?
- Hydrochlorothiazide
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 30 participants
- Where
- 1 siteGermany
- Study dates
- 18 Jan 2021to 22 Jul 2021
- Phase
- Phase 1
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- The subject is willing and able to participate and provides written informed consent;
- Healthy subjects with no concomitant medical conditions;
- Age ≥ 18 years;
- The subject is willing to take HCT 25 mg a day although not clinically indicated;
- The subject is willing to undergo controlled UV-exposition although not clinically indicated;
- Skin type I - IV.
Who cannot join
- History of any cardiac disease;
- History of any dermatologic disease;
- Renal insufficiency (eGFR <60 ml/min/1.73m²);
- Intake of photosensitive substances, especially intake of HCT;
- Frequent, above-average, UV exposition (naturally or artificially);
- Known hypertension;
Show all 15Show fewer
- Known electrolyte disbalance;
- Systolic blood pressure at baseline <100 mmHg;
- Skin type V and VI;
- History of severe diseases, which could endanger the safety of study participant;
- Known unresolved history of alcohol dependency or drug abuse or any other kind of dependencies
- Intake of any of the following medications or substances: Betablockers; nitrates; barbiturates; phenothiazines; tricyclic antidepressants; vasodilatory drugs; ACE-inhibitors; NSAIDs; salicylates; phenytoin; Insulin; oral antidiabetic drugs; vasoconstrictors; glycosides; substances lowering blood-urea levels; substances causing a Long-QT-Syndrome; chinidine; carbamazepine; cyclosporine; cholecalciferol; potassium salts; amantadine; allopurinol; methyldopa; cholestyramine; colestipol; other diuretics; lithium; cytostatic drugs;
- Women in childbearing age and not using medically acceptable effective contraception refer to CTFG: The study population includes female of childbearing potential. Female of childbearing potential have to agree to comply with the applicable contraceptive requirements of the protocol for the duration of the study or having post-menopausal status or be permanently sterilized (at least 6 weeks post-sterilization). Highly effective contraception is defined as a contraceptive method with failure rate of less than 1 % per year when used consistently and correctly and when applicable, in accordance with the product label;
- Subject is pregnant (e.g., positive ß-hCG test) or is breast feeding;
- Hypersensitivity to the active substance, to HCT or any of its excipients.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: A Randomized, Double-blind, Placebo-controlled Study to Evaluate the Influence of Hydrochlorothiazide on Dermal Photosensitivity and DNA Stability - a Pilot Study (HCTox Study)
The clinical trial is designed as a national, prospective, single-center, double-blind, parallel group, randomized, controlled, interventional trial to investigate whether a therapy with HCT compared with placebo can affect dermal photosensitivity and DNA stability.
Read the detailed description
Previously published retrospective analyses leading to the official warning about the use of hydrochlorothiazide (HCT).
The underlying pilot study examins, if the intake of HCT leads to increased dermal photosensitivity and in combination with UV-exposition to a DNA-damage of the skin.
Up until today, there is no prospective, randomized, placebo-controlled trial investigating the impact of HCT on dermal photosensitivity in greater detail. The pilot trial is designed as feasibility study to clarify the impact of HCT on dermal photosensitivity. This may facilitate evidence-based recommendations as to whether or not HCT increases the risk for skin cancer. Of note, HCT is one of most frequently prescribed drugs in Germany.
- Conditions
- Photosensitivity
- Being tested
- Hydrochlorothiazide, Placebo
- Medical subject headings
- Photosensitivity Disorders
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
HydrochlorothiazideDrug
Also called HCT
Please see arm descriptions
PlaceboDrug
Please see arm descriptions
| Study group | Role | What they receive |
|---|---|---|
| Intervention | Experimental | Intake of HCT 25 mg, 1 tablet/d for 15 days Receives: Drug: Hydrochlorothiazide |
| Placebo | Placebo comparator | Intake of Placebo, 1 tablet/d for 15 days Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Changes in subjects´ minimal-erythema-dose (MED).
The MED is the minimal erythema dose, meaning the minimal dose of energy (in this case provided by UV-exposition) per area that leads to a clinically visible skin reaction, mainly a slight reddening.
The MED is assessed by a clinical tool called the light-stair.
Measured: 2 weeks
Amount of excretion of pyrimidine-dimers (PD) in urine.
Changes from Baseline Visit to Day 26
Measured: 26 days
Secondary outcomes (2)
Changes in blood-serum vitamin-D levels.
Changes from Baseline Visit to Day 24
Measured: 26 days
Changes in blood pressure.
Changes from Baseline Visit to Day 24
Measured: 26 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Dec 2020
- Study start18 Jan 2021
- Primary completion22 Jul 2021
- Study completion22 Jul 2021
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (1)Papers the sponsor has linked to this study.
- Other trials for PhotosensitivityStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- National, prospective, single-center, double-blind, parallel group, randomized, controlled, interventional Trial.
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 30 participants (actual)
Sponsor and investigators
- Lead sponsor
- Universität des Saarlandes
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Felix Mahfoud, MD, Principal investigator, Saarland University Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04654312
- Sponsor's protocol ID
- HCTox
- Status last verified
- Jul 2021
- First submitted
- 24 Nov 2020
- Last updated
- 11 Aug 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Gotzinger F, Hohl M, Lauder L, Millenaar D, Kunz M, Meyer MR, Ukena C, Lerche CM, Philipsen PA, Reichrath J, Bohm M, Mahfoud F. A randomized, placebo-controlled, trial to assess the photosensitizing, phototoxic and carcinogenic potential of hydrochlorothiazide in healthy volunteers. J Hypertens. 2023 Nov 1;41(11):1853-1862. doi: 10.1097/HJH.0000000000003558. Epub 2023 Sep 13.
PubMed 37702559
Study at a glance
From the registry record, last updated by the sponsor on 11 Aug 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized, Double-blind, Placebo-controlled Study to Evaluate the Influence of Hydrochlorothiazide on Dermal Photosensitivity and DNA Stability - a Pilot Study (HCTox Study)
- ClinicalTrials.gov ID
- NCT04654312
- Acronym / sponsor ID
- HCTox
- Conditions
- Photosensitivity
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 30 participants (actual)
- Lead sponsor
- Universität des SaarlandesUniversity, hospital or other
- Study start
- 18 Jan 2021 (actual)
- Primary completion
- 22 Jul 2021 (actual)
- Study completion
- 22 Jul 2021 (actual)
- First posted
- 4 Dec 2020 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The clinical trial is designed as a national, prospective, single-center, double-blind, parallel group, randomized, controlled, interventional trial to investigate whether a therapy with HCT compared with placebo can affect dermal photosensitivity and DNA stability.
Detailed description
Previously published retrospective analyses leading to the official warning about the use of hydrochlorothiazide (HCT).
The underlying pilot study examins, if the intake of HCT leads to increased dermal photosensitivity and in combination with UV-exposition to a DNA-damage of the skin.
Up until today, there is no prospective, randomized, placebo-controlled trial investigating the impact of HCT on dermal photosensitivity in greater detail. The pilot trial is designed as feasibility study to clarify the impact of HCT on dermal photosensitivity. This may facilitate evidence-based recommendations as to whether or not HCT increases the risk for skin cancer. Of note, HCT is one of most frequently prescribed drugs in Germany.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
- Model description
- National, prospective, single-center, double-blind, parallel group, randomized, controlled, interventional Trial.
| Arm | Type | Receives |
|---|---|---|
| Intervention | Experimental | Drug: HydrochlorothiazideIntake of HCT 25 mg, 1 tablet/d for 15 days |
| Placebo | Placebo comparator | Drug: PlaceboIntake of Placebo, 1 tablet/d for 15 days |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- The subject is willing and able to participate and provides written informed consent;
- Healthy subjects with no concomitant medical conditions;
- Age ≥ 18 years;
- The subject is willing to take HCT 25 mg a day although not clinically indicated;
- The subject is willing to undergo controlled UV-exposition although not clinically indicated;
Key exclusion criteria (15 listed)
- History of any cardiac disease;
- History of any dermatologic disease;
- Renal insufficiency (eGFR <60 ml/min/1.73m²);
- Intake of photosensitive substances, especially intake of HCT;
- Frequent, above-average, UV exposition (naturally or artificially);
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| HydrochlorothiazideAlso: HCTPlease see arm descriptions | Drug | Intervention |
| PlaceboPlease see arm descriptions | Drug | Placebo |
Primary outcome
Changes in subjects´ minimal-erythema-dose (MED).
Time frame: 2 weeks
The MED is the minimal erythema dose, meaning the minimal dose of energy (in this case provided by UV-exposition) per area that leads to a clinically visible skin reaction, mainly a slight reddening. The MED is assessed by a clinical tool called the light-stair.
Amount of excretion of pyrimidine-dimers (PD) in urine.
Time frame: 26 days
Changes from Baseline Visit to Day 26
2 secondary outcomes
Changes in blood-serum vitamin-D levels.
Time frame: 26 days
Changes in blood pressure.
Time frame: 26 days
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Aug 2025.
- Results publication: PubMed 37702559Gotzinger F, Hohl M, Lauder L, Millenaar D, Kunz M, Meyer MR, Ukena C, Lerche CM, Philipsen PA, Reichrath J, Bohm M, Mahfoud F. A randomized, placebo-controlled, trial to assess the photosensitizing, phototoxic and carcinogenic potential of hydrochlorothiazide in healthy volunteers. J Hypertens. 2023 Nov 1;41(11):1853-1862. doi: 10.1097/HJH.0000000000003558. Epub 2023 Sep 13.
- Hydrochlorothiazid - Risiko von nichtmelanozytärem Hautkrebs \[Basalzellkarzinom (Basaliom); Plattenepithelkarzinom der Haut (Spinaliom): Rote-Hand-Brief vom 17. Oktober 2018.Link provided by the sponsor.
- Individual participant dataSharing planned: No
Related trials for Photosensitivity
RecruitingObservational study
Skin Type Determination Using Image Artificial Intelligence
Skin Ageing, Skin
RecruitingPhase 2
Study of Remibrutinib (LOU064) Efficacy and Safety and Exploration of Its Mechanism of Action in Participants With Chronic Urticaria
Chronic Urticaria (CU): Chronic Inducible Urticaria (CINDU) and Chronic Spontaneous Urticaria (CSU)
Not yet recruiting
Randomized Trial of a Sun Safety Intervention for Young Adults
Sunburn
Active, not recruitingPhase 3
Undergraduate Skin Cancer Prevention Trial
Skin Cancer
RecruitingObservational study
Natural History Study for DNA Repair Disorders
DNA Repair Disorder, Cockayne Syndrome
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Felix Mahfoud, MD principal investigator
Saarland University Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Hydrochlorothiazide in people with Photosensitivity, run by Universität des Saarlandes at 1 site in Germany.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 15 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 11 Aug 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Germany. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Changes in subjects´ minimal-erythema-dose (MED). (time frame: 2 weeks). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04654312, which also lists 1 linked publication.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Aug 2025.