L4 - Pharmacology Of Anemia Flashcards
What the most common sx of anemia?
Fatigue, dizziness, pale skin, cold hands and feet, shortness of breath and irregular heart beat
What are other sx of anemia?
Low BP, palpitations, rapid heart rate, chest pain, angina, heart attack, splenomegaly, yellowing of the eyes, pale skin, cold skin, SOB, muscle weakness, changes in stool color
Iron loss typically occurs via what?
Routine blood loss and sloughing of cells
No renal mechanism for elimination of excess iron
Iron absorption is regulated by what?
Hepcidin
Capacity of hepcidin to block iron absorption can be overwhelmed by excess intake or bypassed by iron infusion
If there is an increase in hepicidin what occurs?
Decreased iron by blocking ferroportin mediated iron absorption
What are the cases of microcytic anemia?
Reduced iron availability (severe iron deficiency is MC)
Reduced heme synthesis due to lead poisoning, conventional or acquired sideroblastic anemia
Reduced globin production due to thalassemic disorders, other hemoglobinopathies
Rare disorders due to defects in iron absorption, transport, utilization and recycling
Why are RBCs so large in macrocytic anemia?
Erythroblasts doubled their protein in anticipation of division but were unable to synthesize new DNA
Extrusion of nucleus leaves behind a large cell
What needs to be measured if a folate or vitamin B 12 deficiency is suspected?
B12 and folate levels as well as MMA and homocysteine levels
Vitamin B12 is important for what?
Metabolism, the formation of RBCs, and the maintenance of the CNS which includes the brain and spinal cord
Where can vitamin B12 be found?
Found in animal products such as fish, meat, poultry, eggs, milk and milk products
Generally not present in plant foods but fortified breakfast cereals are available for vegetarians
How much vitamin B12 do we need daily?
2 ug/day (usual diet contains 5-7)
How much Vitamin B12 does the body store in the liver?
2-5mg
Because the normal body stores greatly exceed the daily requirement it takes years to develop vitamin B12 deficiency after normal absorption ceases
What can inactivate cyanocobalamin (common form of vitamin B12?
Nitrous oxide, inhaled analgesia during surgery
If body stores of Vitamin B12 are depleted what can occur?
Rapid onset of neurologic dysfunction (e.g. paresthesia, weakness, spasticity) that may not fully reverse
Describe the absorption of vitamin B12
Cbl is liberated from food by actions of acid and pepsin
R factors in saliva and gastric juice bind Cbl
Cbl is freed from R factors in alkaline pancreatic enzyme juice of duodenum
Cbl then finds to IF (which is secreted by parietal cells along with gastric acid)
The IF-Cbl complex then binds to a specific receptor, cubulin, in the ileum and is absorbed in an energy requiring process
What is a common cause of vitamin B12 deficiency?
Pernicious anemia
Other causes include gastrectomy or gastritis and H pylori infection
What can cause pernicious anemia?
Auto Ab formation - two types:
- Blocks IF-Cbl interaction
- Blocks IF-Cbl receptors in ileum
Chronic atrophic gastritis due to auto Abs directed against the H K ATPase of the parietal cells
What are the sx of vitamin B12 deficiency?
Vitiligo, hyperpigmentation and jaundice
Glossitis
Anemia (macrocytic, megaloblastic), neutropenia (hypersegmented neutrophils), thrombocytopenia
Paresthesia, numbness, gait abnormalities, cognitive impairment, irritability, weakness
What is the function of folate in the body?
Aids in the production of RBCs and the synthesis of DNA
Works with B12 and vitamin C to help the body digest and utilize proteins
What are the best sources of folate?
Obtained from yeast, liver, kidney, and green leafy vegetables
What are the daily requirements for folate intake?
Daily requirement is 5-50ug/day but recommended daily allowance is 400ug/day for adults and 800ug/day for pregnant and lactating women
Describe folate absorption
Absorbed in jejunum, enters plasma, rapidly cleared by hepatocytes and other cells where its trapped by polyglutamation
Plasma levels fall within 3 weeks of inadequate intake due to metabolism and urinary excretion
Undergoes extensive enterohepatic circulation; levels fall wihtin 6 hrs if this is disrupted
What is the usual cause of folate deficiency?
Inadequate dietary intake or alcoholism
But malabsorption in jejunum can also be its cause
What are the sx of folate deficiency?
Jaundice, mouth ulcers, macrocytic megaloblastic anmeia, neutropenia, thrombocytopenia, neuropsychiatric sx are rare
Deficiency during pregnancy causes neural tube defects in fetus
The kidney releases erythropoietin in response to what?
Hypoxia
What is the MOA of epoetin Alfa?
A 165 amino acid erythropoiesis stimulating glycoprotein
What are the effects of epoetin Alfa?
Stimulates erythropoiesis
Increases reticulocyte counts in <10 days
What are the clinical applications for epoietin Alfa?
Anemia due to CKD or cancer chemo
Use banned by international Olympic committee
What are the pharmacokinetics for epoetin Alfa?
Administered IV or SC
What are the toxicities of epoetin Alfa?
20-50% have increase DAP >10mmHg despite keeping Hct in 3-35 range
Increased risk of death, MI, stroke, VTE, tumor progression