As i could make out from brief description, that person is having chronic kidney disease with stable serum creatinine at 2.4 mg/dl. But the concern is recent rise in urea level.
There could be various reasons for this like Dehydartion due to diarrhea, vomiting or any fluid loss from any cause or infection etc.
Few advice : Avoid any drugs which have toxic effects on kidney. Take medication only on doctors advice. Monitor water intake and urine output.
You should consult a nephrologist for detailed evaluation.