76
PHYSIOLOGICAL MONITORING OF THE STANDARD PICOSALAX REGIMEN FOR COLON CLEANSING IN HEALTHY VOLUNTEERS REVEALS SUBCLINICAL CHANGES IN ELECTROLYTES AND THE QT CORRECTED INTERVAL
A Rahman, S Vanner, L Hookey
Queen's University, Kingston, Ontario
Aims: Picosalax is used widely in Canada and other countries for colon cleansing prior to colonoscopy. This is a low volume osmotic agent with the potential to deplete intravascular volume and alter electrolyte balance yet there is little data on its effects on these clinically important endpoints. Therefore, the aim of this study was to serially measure parameters of intravascular volume and electrolyte status in healthy volunteers over a 24 hr period using the standard 2 sachet dosing.
Methods: Twenty healthy volunteers over the age of 45 were studied. Patients consumed clear fluids 20 hr prior to the first dose of Picosalax. One sachet of Picosalax was administered at time 0 and the second at time 5 hr as per the traditional use. Electrolytes, postural vital measurements and adverse event reports were made at 0, 2, 4, 5, 7, 9, 12, and 24 hr. EKGs and weight measurements were performed at 0, 5, 12 and 24 hours. Patients drank ~ 2-3 L of clear fluids during the study period.
Results: There was a significant decrease from time 0 to time 12 hr in K+ levels (mean = 3.8 to 3.3 mEq/L; normal >= 3.5, range 2.8-4.4) (p<.05) but not at 24 hr. The proportion of patients with hypokalemia at 0, 5, 12, and 24 hours were 15%, 35%, 75%, and 10%.
Ionized Ca2+ levels also decreased significantly from time 0 to time 12 hr (mean = 1.24 to 1.17mEq/L; normal >=1.19, range 1.06 to 1.31) (p<0.05) but normalized by time 24 hr. The proportion of patients with low Ca2+ levels at 0, 5, 12, and 24 hr were 10%, 55%, 65%, and 20%.
Compared to time 0 hr, there was a significant increase in Mg2+ levels at both time 12 and 24 hours (mean= 0.90,0.99,0.95, normal =< 1.00, range 0.80 to 1.17) (p<0.05). The proportion of patients with hypermagnesmia at 0, 5, 12, and 24 hours were 5%, 45%, 35%, and 20%.
Mean serum Na+, creatinine, and PO4- levels remained within reference range with no differences between time 0, 12 and 24 hr.
There was an increase in QTc intervals from time 0, 12, and 24 hr which were 404, 415 and 420 ms with a statistically significant increase from time 0 compared to time 24 hr (p<0.05). No patients were symptomatic from electrolyte changes.
No adverse events were reported. There was no significant changes in weights, or postural vitals.
Conclusions: The proportion of individuals with hypokalemia, hypocalcemia and hypermagnesmia at 5 and 12 hours following 2 sachets of picosalax is large but the magnitude of the changes do not appear clinically relevant. Nonetheless, they could have implications in patients with pre-existing electrolyte abnormalities or renal dysfunction. Changes in QTc interval could also be clinically important for patients with underlying conduction disorders. These findings also raise questions concerning the safety of dosing of greater than 2 sachets.