8132 Background: Most common toxicities of CAP include diarrhea, nausea, vomiting, and HFS. Hypokalemia has not been reported frequently with CAP. We performed a retrospective study to determine incidence, risk factors, complications and management of hypokalemia in pts receiving CAP. Methods: We identified 63 pts who received CAP b/w Apr 2002 and Nov 2004. Hypokalemia was defined as K+ level < 3.2 mEq/L. Exclusion criteria included presence of vomiting or diarrhea, concomitant use of diuretics or antibiotics (PCN, Gent, Amph), hypomagnesemia, h/o hypokalemia prior CAP, renal insufficiency, thyroid or adrenal dysfunction and diabetic nephropathy. Pts were classified into 3 groups based on K+ levels: mild (3.0–3.2 mEq/L), moderate (2.5- 2.9 mEq/L) and severe (< 2.5 mEq/L). Results: Among 63 pts (age: 32–89 yr; M/F: 33/30), 54 met the criteria. Diagnoses included: 31 pancreas, 19 colon, 3 liver and 1 stomach cancer. 5 pts (9%) received CAP alone, 15 (28%) with XRT and 34 (63%) with oxaliplatin or CPT-11. Dose of CAP ranged b/w 1000 - 2000 mg/m2. Diagnosis of hypokalemia occurred after an average of 84 days of CAP administration. Overall, 11 pts (20%) developed hypokalemia. According to classification: 8 (73%) had mild, 2 (18%) moderate and 1 (9%) severe. No cardiac or neuromuscular complications noticed. Replacement of K+ was required in 6 pts (11%) (2 IV, 4 oral). Continued replacement > 4 wks was required in 2 pts (4%). No pt had to stop CAP due to hypokalemia. One pt (2%) had persistent hypokalemia (> 4 wks) after stopping CAP. Normalization of K+ levels was achieved in 91% of pts. Four pts (7%) were on K+ sparing diuretics for ascites and never developed hypokalemia. No correlation in creatinine and hypokalemia noticed. Mean urine K+ was 28 mEq/L suggesting renal loss. Conclusions: Hypokalemia was encountered in 20% of pts on CAP without any obvious etiology. The incidence of hypokalemia might be higher as few pts were on K+ sparing diuretics. Since regulation of K+ homeostasis depends on normal renal function, we postulate that hypokalemia may be related to the effect of CAP on renal tubules. Due to potential complications, hypokalemia in pts on CAP deserves special diagnostic and therapeutic attentions. Further analysis to characterize the mechanism is needed. No significant financial relationships to disclose.