Methylene blue MMX tablets for chromoendoscopy. Safety tolerability and bioavailability in healthy volunteers

Methylene blue-MMX tablets are proposed as colonic diagnostic staining. Methylene blue taken prior to colonoscopy is expected to provide an effective staining of colonic and rectal mucosa leaving unstained the dysplastic or polypoid areas. The present single dose, open-label study investigated the safety of methylene blue after single oral doses of 200 and 400mg in healthy volunteers. The absolute bioavailability was also investigated after the intake of 2L of bowel cleansing preparation in 2h and by comparing the dose of 200mg with a single iv dose of 100mg in the same subjects. Only non-serious adverse events occurred. Related events occurred to 8/22 subjects. Most of the events were mild and transient. Abnormal transaminases, gastrointestinal disorders and dysuria frequency were 13.6%. After intake of the laxative and the oral dose of 200mg, systemic exposure to methylene blue was shown in all subjects with concentrations increasing for 12h. The peak was reached in a median of 16 h. Peak blood concentration did not increase proportionally with the dose. AUC(0-t) was 32.94 μg/mL × h after 200mg and 38.08 μg/mL × h after 400mg. Half life ranged between 14 and 27 h after the lower dose and between 6 and 26 h after the higher dose. The cumulative excretion was about 40% of the injected dose, 39.67% after 200mg and 23.48% after 400mg. Absolute bioavailability of methylene blue calculated as ratio between AUC(0-t) oral/iv corrected for the dose was on average F(abs)=139.19 ± 52.00%.