- Patients should not have known hypersensitivity to boron, mannitol, or PS-341; if day 28 or 42 falls on a weekend or holiday, the limit may be extended to the next working day; in calculating days of tests and measurements, the day a test or measurement is done is considered day 0; therefore, if a test is done on a Monday, the Monday four weeks later would be considered day 28; this allows for efficient patient scheduling without exceeding the guidelines