Doxycycline assay hair samples for testing long-term compliance treatment

- Photosensitivity affects the quality of life of patients treated with long-term doxycycline.
- Hair samples can be used to test long-term compliance in patients to explain failures or relapses.
- Ultra-high performance liquid chromatography assay was used to test doxycycline levels in samples.
- The levels of doxycycline in the hair samples decrease significantly over time.

SummaryObjectivesMany patients undergoing long-term doxycycline treatment do not regularly take their treatment because of photosensitivity. Our objective was to create an assay for determining doxycycline levels and to use hair samples for monitoring the compliance over a longer period of time.MethodsWe tested sera and hair samples from patients treated with doxycycline by a suitable ultra-high performance liquid chromatography (UHPLC) based assay.ResultsWe estimated that the speed of hair growth is roughly 1.25 cm per month and we were able to determine doxycycline levels over a 6-month period. We tested 14 patients treated with doxycycline and we found similar levels of doxycycline in the serum and the hair samples representing the last 4 months. Linear regression analysis revealed that the level of doxycycline in the serum remained stable over time (p = 0.7) but the level of doxycycline in the hair decreased significantly over time (p = 0.03) indicating a degradation of this molecule in the hair. We detected two patients who did not have antibiotic in the hair, indicating a lack of compliance that was also confirmed by interview.ConclusionHair samples can be used to test long-term compliance in patients to explain failures or relapses.