Rituximab; Uses, Dosage, Side Effects, Drug Interactions

Rituximab; Uses, Dosage, Side Effects, Drug Interactions

Rituximab is a genetically engineered chimeric murine/human monoclonal antibody directed against the CD20 antigen found on the surface of normal and malignant B lymphocytes. The antibody is an IgG1 kappa immunoglobulin containing murine light- and heavy-chain variable region sequences and human constant region sequences. Rituximab is composed of two heavy chains of 451 amino acids and two light chains of 213 amino acids. It is used for non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, rheumatoid arthritis, idiopathic thrombocytopenic purpura, pemphigus vulgaris and myasthenia gravis. It is given by slow injection into a vein.

Mechanisms of Action of Rituximab

Rituximab mechanisms of action; the three major independent mechanisms are (1) antibody dependent cellular cytotoxicity (ADCC), (2) complement mediated cytotoxicity (CMC), and (3) apoptosis; subset panel illustrates a schematic view of CD20 structure and rituximab.
Rituximab binding to CD20. The CD20 proteins are sticking out of the cell membrane, and rituximab, the Y-shaped antibody, is binding to the CD20 proteins. The antibody binds to the cell surface protein CD20. CD20 is widely expressed on B cells, from early pre-B cells to later in differentiation, but it is absent on terminally differentiated plasma cells. CD20 does not shed, modulate or internalize. Although the function of CD20 is unknown, it may play a role in Ca2+ influx across plasma membranes, maintaining intracellular Ca2+ concentration and allowing activation of B cells.

Rituximab tends to stick to one side of B cells, where CD20 is, forming a cap and drawing proteins over to that side. The presence of the cap changed the effectiveness of natural killer (NK) cells in destroying these B cells. When an NK cell latched onto the cap, it had an 80% success rate at killing the cell. In contrast, when the B cell lacked this asymmetric protein cluster, it was killed only 40% of the time.

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The following effects have been found:

  • The Fc portion of rituximab mediates antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC).
  • Rituximab has a general regulatory effect on the cell cycle.
  • It increases MHC II and adhesion molecules LFA-1 and LFA-3 (lymphocyte function-associated antigen).
  • It elicits shedding of CD23.
  • It downregulates the B cell receptor.
  • It induces apoptosis of CD20+ cells.

The combined effect results in the elimination of B cells (including the cancerous ones) from the body, allowing a new population of healthy B cells to develop from lymphoid stem cells.

Rituximab binds to amino acids 170-173 and 182-185 on CD20, which are physically close to each other as a result of a disulfide bond between amino acids 167 and 183.

Indications of Rituximab

  • Chronic lymphocytic leukemia
  • Evan’s syndrome
  • Non-Hodgkin’s lymphoma
  • Bullous pemphigoid
  • Diffuse Large B-Cell Lymphoma
  • Focal segmental glomerulosclerosis
  • Follicular lymphoma
  • Idiopathic thrombocytopenic purpura
  • Mantle cell lymphoma
  • Microscopic polyangiitis
  • Pemphigoid
  • Pemphigus
  • Rheumatoid arthritis
  • Wegener’s granulomatosis
  • Granulomatosis with polyangiitis
  • Microscopic polyangiitis

Contra-Indications of Rituximab

  • Herpes simplex infection
  • Disease caused by cytomegalovirus infection
  • Infection caused by a fungus
  • Pneumonia caused by Pneumocystis Jirovecii Organism
  • Severe infection
  • The high amount of phosphate in the blood
  • Low amount of calcium in the blood
  • The high amount of potassium in the blood
  • Anemia
  • Decreased Blood Platelets
  • Decreased Neutrophils a Type of White Blood Cell
  • Angina
  • Abnormal heart rhythm
  • Stomach or Intestine Blockage
  • Acute Renal Failure
  • Kidney disease with a reduction in kidney function
  • A mother who is producing milk and breastfeeding
  • Infection caused by the Varicella Zoster Virus
  • A Rupture in the Wall of the Stomach or Intestine
  • Resolved hepatitis B
  • Relapse of Hepatitis B Infection Symptoms
  • Hypogammaglobulinemia
  • Hepatitis C
  • Progressive Disease in the White Matter of the Brain
  • Disease due to West Nile Virus
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Side Effects of Rituximab

The most common

More common

Less Common

Drug Interactions of Rituximab

Pregnancy & Lactation

FDA Pregnancy Category C


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This medication is not recommended for use during pregnancy. If you may become pregnant, use an effective method of birth control while you are using this medication, and for at least 12 months after the last treatment. Tell your doctor immediately if you become pregnant.


It is not known if rituximab passes into breast milk. If you are breast feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding




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