Inclusion Criteria:  Patients who have tolerated the maximum rate of intravenous administration of rituximab (400 mg/h) in the first or second infusion. The last rituximab infusion must have occurred within the last 3 months. All patients receiving rituximab can be included, regardless of whether they receive rituximab as monotherapy or in combination with chemotherapy and regardless of the line in which they are receiving it. Patients will be included in both induction and maintenance treatment. All patients must sign the informed consent form.  Exclusion Criteria:  Patients with initial absolute lymphocyte count >10x10^3 cells/µL. Patients who have presented hypersensitivity and severe adverse effects (grade II or higher) in the first or second infusion. Severe heart failure (NYHA class III-IV) or uncontrolled severe cardiac disease. Respiratory failure, severe uncontrolled COPD/asthma. Patients allergic to premedication: acetaminophen or polaramine. Severe active infection. Pregnant patients. Refusal to participate.