Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
NSAIDs should be administered several days before the start of menstruation in order to block the endometriosis-associated prostaglandin formation that leads to pain and swelling. NSAIDs prevent prostaglandin E2 (PGE2) production through reversible blockade of COX-1 and COX-2. Nonprescription formulations (ibuprofen and naproxen) should be taken according to the manufacturer's dosing instructions, and a prescription may be obtained from a physician if a higher dose is required. For the treatment of endometriosis, the highest NSAID dose tolerated by the patient should be administered. If the first NSAID is not effective after 4 to 6 weeks, another NSAID should be tried because of the variability in drug response among individuals. No NSAID has been observed to be superior to another. For the management of endometriosis, an NSAID may be combined with another pharmacologic agent, such as a hormonal preparation (discussed in upcoming sections).
Patients with a known aspirin allergy, bronchial asthma, and nasal polyps—often referred to as the aspirin triad—should avoid the use of NSAIDs, as cross-sensitivity reactions can occur. NSAIDs should be administered with plenty of water and on a full stomach. This is to protect the gastrointestinal tract from the loss of cytoprotective PGE2. Likewise, patients with a history of gastric irritation, ulceration, and bleeding should avoid COX-1 inhibitors. NSAIDs should not be administered on a chronic basis; renal injury can result from the loss of PGE2-mediated vasodilation in the afferent arteriole of the kidney, leading to a reduction in glomerular filtration rate through reduced blood flow. NSAIDs can also negate the effects of antihypertensives and the antiplatelet action of aspirin while increasing the toxicity of the mood stabilizer lithium.
Combined estrogen-progestin contraceptives and progestin-only preparations reduce endometrial proliferation, blocking the inflammation and pain associated with endometriosis. The decreased ovulation afforded by these agents is protective against epithelial ovarian and endometrial cancers, which are associated with endometriosis. Gonadotropin-releasing hormone (GnRH) agonists, danazol, and aromatase inhibitors should also be considered.
Combined Estrogen-Progestin Contraceptives
These drugs, which are available in pill, transdermal patch, and vaginal ring formulations, are considered an appropriate treatment option for the pain of endometriosis until pregnancy is desired. Contraceptives reduce ovarian function by inhibiting the secretion of gonadotropins (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]). These drugs downregulate cell proliferation and enhance apoptosis in the eutopic endometrium. Serious adverse effects of estrogenprogestin combinations are lower than in previous years because the formulations contain a lower estrogen dose. However, the risks of thromboembolism, cerebrovascular disease, and coronary artery disease, which are attributed to the estrogen component of the formulation, cannot be eliminated. Smoking, especially in women older than 35 years, remains a contraindication to the use of combined estrogen-progestin contraceptives. It is also inadvisable for patients with a history of estrogen-dependent cancer to use these formulations. For the treatment of endometriosis, hormonal birth control should be administered continuously (skipping the placebo tablets) for 3 months or more in order to achieve less-frequent menstrual periods and consequently less pain.
This therapy is appropriate for patients who do not respond to or have a contraindication to estrogen-progestin contraceptives. Progestins bind to nuclear receptors, leading to enhanced gene transcription and suppression of gonadotropin synthesis. In addition, progestins prevent the implantation and growth of regurgitated endometrial cells by inhibiting angiogenesis and matrix metalloproteinases. Norethindrone is started at 5 mg per day for 14 days and increased in increments of 2.5 mg per day to reach 15 mg per day, which is continued for 6 to 9 months or until the occurrence of breakthrough bleeding (when the uterine lining becomes thin). Medroxyprogesterone may be administered as an SC injection at a dosage of 150 mg every 3 months. In addition to breakthrough bleeding, progestin-only preparations can induce breast tenderness and acne. Weight gain is possible given the stimulation of insulin secretion and increased appetite.
Although limited results are available on the use of the levonorgestrel-releasing intrauterine system to treat endometriosis, this device has improved patient compliance over the once-daily oral progestin formulations because there is no repeated administration. Levonorgestrel enhances endometrial glandular atrophy and promotes endometrial apoptosis, resulting in a decrease in proliferation.
This agent is a synthetic androgen with minimal estrogen or progesterone potential. Danazol suppresses the activity of the ovary by inhibiting steroidogenic enzymes and preventing midcycle FSH and LH release. Because it can bind to glucocorticoid receptors, danazol also has been observed to modulate immunologic function. Danazol is administered orally in divided doses ranging from 400 mg to 800 mg daily for 6 to 9 months in mild cases; severe cases may require 800 mg per day in two divided doses. The increase in liver injury, masculinization, and risk of thromboembolism limits the use of danazol for endometriosis treatment. This drug is teratogenic and should be avoided in patients considering pregnancy. Abrupt discontinuation of danazol has been linked to idiopathic intracranial pressure (or pseudotumor cerebri), which may be due to a rebound phenomenon of cerebral vascular tone or prolonged effects of the drug's metabolites.
These drugs bind to and downregulate pituitary gland receptors. The initial surge of LH and FSH may exacerbate endometriosis pain because of the ovarian stimulation. However, 2 weeks after therapy initiation, an estrogen-deficient state occurs; this is the mechanism of leuprolide and goserelin for endometriosis management. GnRH agonists also enhance apoptosis and decrease cellular proliferation in the endometrial cells. Some expected adverse effects are hot flashes, vaginal dryness, and atrophy. Since a hypoestrogenic state is induced, accelerated bone loss can occur in patients treated long-term with these agents. Therefore, an appropriate add-back regimen—the addition of a small amount of either estrogen and progesterone or progesterone alone—to lessen these toxicities should be considered. Leuprolide may be used in combination with norethindrone 3.75 mg per month for up to 6 months or norethindrone 11.25 mg every 3 months for up to two doses (total 6-month duration). Goserelin is administered at 3.6 mg every 28 days for 6 months.
Although further research is required, GnRH antagonists such as degarelix are being studied as possible management options for endometriosis. These drugs differ from GnRH agonists in that, instead of downregulation, there is a competitive blockade at the pituitary GnRH receptor. Gonadotropins are suppressed without the initial flare of estrogen.
Aromatase activity is absent in the normal endometrium but is increased in patients with endometriosis. This enzyme is involved in the conversion of androstenedione to estrone and testosterone to estradiol. Increased estrogen production stimulates the synthesis of PGE2, leading to inflammation. Although considered an off-label use, aromatase inhibitors have been found beneficial for patients with postmenopausal endometriosis given the competitive blockade offered by letrozole and anastrozole. Long-term treatment with aromatase inhibitors has been associated with bone loss, so vitamin D or bisphosphonates are sometimes added to the regimen to prevent this deleterious effect. For the management of endometriosis, aromatase inhibitors are taken orally once daily and may be given concurrently with combined estrogen-progestin contraceptives, progestins, or GnRH agonists.
Table 1 summarizes the pharmacologic options recommended for endometriosis management.
Surgical evaluation and treatment via laparoscopy is considered if drug therapy is unsuccessful, a pelvic mass is detected, or the patient is considering pregnancy. Conservative surgery is considered first-line treatment, as it is less invasive and preserves fertility because much of the uterus and ovary are preserved.
US Pharmacist. 2017;42(9):12/16/2017 © 2017 Jobson Publishing