O inhibition of the enzyme is the major role of the

This preview shows page 74 - 77 out of 142 pages.

o Inhibition of the enzyme is the major role of the class of aromatase inhibitors. The drugs approved for use in postbreast cancer treatment in women are the primary focus of this section Pharmacokinetics o Anastrazole (Arimidex) and letrozole (Femara) are nonsteroidal medications that create a reduction in circulating estrogens. Exemestane (Aromasin) is classified as a steroidal agent. All are oral medications. Anastrozole and letrozole are well absorbed with or without food; exemestane has increased circulating levels if taken after a fatty meal o Fecal elimination accounts for 90% of anastrazole after metabolism. Exemestane has a 45% urine elimination with the rest in the feces. Ninety percent of letrozole is excreted in the urine.
o Renal dosing is not required of any of three agents discussed Pharmacotherapeutics o Aromatase inhibitors are used as adjuvant therapy in estrogen receptor positive postmenopausal breast cancer patients. They are added to the plan after 3 to 5 years of tamoxifen therapy and continued for at least 5 years. They are also used as first-line treatment in cases of advanced or metastatic cancer. There are unlabeled uses for ovarian cancer and to stimulate ovulation in anovulatory women done within specialty care o The aromatase inhibitors are oral agents taken once daily. Anastrazole is given as a 1 mg tablet, exemestane is a 25 mg tablet, and letrozole comes in a 2.5 mg dose. There is no increasing in dosage over time. o All forms of these medications are considered hazardous agents that require special handling and disposal. All are contradindicated in pregnancy and breast feeding Adverse Drug Reactions o Adverse effects for the drug class include various pain syndromes, vertigo, insomnia resulting in daytime sleepiness and confusion, increased risk of blood clots, and hair loss. A key concern is the loss of bone mass. Bone loss can be significant when considering the concurrent osteoporotic risks of postmenopause o All patients should be on calcium and vitamin D supplementation o Hypertension occurs in 10% of patients. A life-threatening increase in blood clotting can result in MI, stroke, or pulmonary embolus. Hot flashes can be intense Drug Interactions o Drug interactions vary by agent, but none should be taken with tamoxifen or an estrogen product. o Anastrazole cannot be taken with pimozide. o Both anastrazole and letrazole will decrease the effect of digoxin and vitamin K antagonists. o Exemestane should not be taken with axtinib or simeprevir. It will decrease the effect of aripiprazole and saxagliptin and increase the effect of methadone and vitamin K antagonists. o Letrozole cannot be taken with tegafur Education and Lifestyle Management o Patient education follows the standards for how to take the medication, when to report adverse effects, and the need for close monitoring of LFT labs o Patients should be encouraged to discuss issues of pain and fatigue with the provider prior to just stopping the medications.

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture