Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

In the 1970s, the average lifespan for patients diagnosed with sickle cell disease was 14 years. Today, the average lifespan has increased to 50 years and beyond (TriHealth, 2012). The patient prognosis for many other hematologic disorders such as hemophilia and cancer continue to improve as well. This can be attributed to advancements in medical care—specifically drug therapy and treatment. When managing drug therapies for patients, it is essential to continuously examine current treatments and evaluate the impact of patient factors on drug effectiveness. To prepare for your role as an advanced practice nurse, you must become familiar with common drug treatments for various hematologic disorders seen in clinical settings. Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

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Select one of the following hematologic disorders: anemia, hemophilia, cancer, sickle cell anemia, thalassemia, thrombolytic disorders, or white blood cell disorders. Consider the types of drugs that would be prescribed to patients to treat symptoms associated with this disorder.

Select one of the following factors: genetics, gender, ethnicity, age, or behavior. Reflect on how this factor might impact the effects of prescribed drugs, as well as any measures you might take to help reduce negative side effects.

With these thoughts in mind:

Post a description of the hematologic disorder you selected including types of drugs that would be prescribed to patients to treat associated symptoms. Then, explain how the factor you selected might impact the effects of prescribed drugs, as well as any measures you might take to help reduce negative side effects.

Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

Description of Sickle Cell Anemia

Sickle Cell Anemia is a genetic condition that is characterised by haemolysis of defective red blood cells (RBCs). It is caused by a mutation of the beta-globin gene that substitutes the 6th amino acid to valine from glutamic acid. The patient becomes homozygous (nn) as opposed to heterozygous (nN) for the defective beta-haemoglobin S (Hb S) allele (Huether & McCance, 2017; Jameson et al., 2018, p. 692). It is the most severe form by which sickle cell disease manifests itself. Autosomes are the 22 human chromosomes which are not sex chromosomes (X or Y). Sickle Cell Anemia is a homozygous autosomal recessive condition (Hammer & McPhee, 2014, p. 8). This means that it only manifests itself clinically if a person inherits the defective gene from each parent. If the person inherits the gene from only one parent, but inherits the normal one from the other parent, he does not fall sick. He will be heterozygous (nN) and thus have the sickle cell trait, but no clinical symptoms. This is because the gene is recessive as opposed to being dominant. Since Sickle Cell Anemia is genetic in aetiology, it cannot be cured at present. It is most prevalent in people of Black descent where the incidence is 1:400 in this population in the United States of America. Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

The pathophysiology of this condition revolves around the abnormal biochemical changes that occur with the substituted 6th amino acid in the beta-globin chain of Hb S, valine. These changes are triggered by de-oxygenation, dehydration, a low pH (acidemia), low outside temperatures, and a raised reticulocyte count. Hypoxemia therefore makes valine change biochemically (polymerise), forming abnormal compounds (Huether & McCance, 2017). These cause the RBCs to reversibly change into the sickle shape. Their cell membranes become sticky and they become inflexible, unable to squeeze through the terminal capillaries to deliver oxygen to the tissues (Jameson et al., 2018, p. 692). The result is widespread occlusion of capillaries and venules all around the body (Katzung, 2018, p. 592). The distal tissues and organs are starved of oxygen and necrose, blood becomes thicker and slow, and a vicious cycle is set. The process only stops when adequate oxygenation and hydration status are re-established.  Hemolysis or destruction of the sickled RBCs then occurs in the spleen where they are pooled. With time, damage to the spleen occurs and the patient then becomes easily susceptible to infections. As a result, they will normally have a low Hb of between 7-10g/dl; a hematocrit of between 20-30%, and a high reticulocyte count (Katzung, 2018, p. 592). Blockage of the minute blood vessels leads to severe pain in the joints, bones, and chest. Ischemic stroke may also occur due to compromised blood flow to the brain, as a result of the blockages. In all this, one factor that may impact the effects of the drugs used to manage this condition is genetics.

Drug Management of Sickle Cell Anemia

As stated, this condition is genetic in origin. As such, current drug treatment only aims to relieve the symptoms, control infections, alleviate suffering, and improve the quality of life. It cannot be cured by drugs, and gene therapy is still under research. Some of the drugs used to treat sickle cell anemia and their side effects are therefore as follows:

  1. Morphine

This is an opioid analgesic that is given when the patient is in a crisis with severe pain. The dosage will range between 0.1-0.5mg/kg every 3-4 hours (Jameson et al., 2018, p. 694). The adverse effects include tolerance and physical dependence, hyperalgesia (lowered pain threshold), respiratory depression, cough suppression, nausea and vomiting, truncal musculoskeletal rigidity, constipation and lowered libido (Katzung, 2018, p. 559-562). Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

  1. Hydroxyurea (hydroxycarbamide)

This is a chemotherapeutic agent originally used to treat cancer. It has been proved to alleviate the severe pain occasioned by the blockage of capillaries and venules by sickled cells. It acts by increasing the production of fetal haemoglobin gamma (HbF). HbF interferes with the polymerisation of valine in sickle cell haemoglobin (HbS). Its adverse effects include hematopoietic depression, gastrointestinal disturbances, and teratogenicity in pregnant women (Katzung, 2018, p. 592). It is given 10-30mg/kg/day (Jameson et al., 2018, p. 694).

  1. Ketorolac (Toradol) and Tramadol

Ketorolac is a non-steroidal anti-inflammatory agent (NSAIA), given 30-60mg STAT then 15-30mg 8 hourly (Jameson et al., 2018, p. 694). Tramadol is a narcotic analgesic. They are given for moderate pain. Side effects include headache, dizziness, and abdominal pain.

  1. Nitrous Oxide (“laughing gas”)

It is given for short term pain relief by inhalation. It causes excessive sweating and dizziness.

  1. Decitabine (5-deoxyazacytidine)

It is an anti-cancer drug that also raises the levels of fetal haemoglobin (HbF).

  1. Antibiotics

State-of-the-art cephalosporin penicillin antibiotics can be given to treat infections.

The Impact of Genetics on Drugs and Reduction of Negative side Effects

The genetic factor will of course impact the effectiveness of the prescribed drugs among the above. This impact is in the fact that these drugs are not pharmacodynamically engineered to treat the underlying cause, which is genetic in nature. Therefore the effect is a reduction in efficacy; in as far as eradication of symptoms is concerned. In other words, genetics makes the drugs unable to cure the sickle cell anemia.

The measures, therefore, that can be taken to reduce the negative side effects of the drugs above may include:

  • Titrating the dosage against the response to treatment, lowering when pain reduces
  • Avoiding unnecessarily prolongation of treatment, especially with the opioids
  • Encouraging ingestion of copious amounts of water to discourage sickling, hence avoiding the need for taking medications.


Hammer, D.G., & McPhee, S.J. (Eds) (2014). Pathophysiology of disease: An introduction to clinical medicine, 7th ed. New York, NY: McGraw-       Hill Education.

Huether, S.E., & McCance, K.L. (2017). Understanding pathophysiology, 6th ed. St. Louis, MO: Elsevier, Inc.

Jameson, J.L., Fauci, A.S., Kasper, D.L., Hauser, S.L., Longo, D.L., & Loscalzo, J. (Eds) (2018). Harrison’s principles of internal medicine, 20th ed. New York, NY: McGraw-Hill Education.

Katzung, B.G. (Ed) (2018). Basic and clinical pharmacology, 14th ed. New York, NY: McGraw-Hill Education.

Sickle Cell Anemia: Genetic Etiology, Pathophysiology, and Drug Treatment

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