Drug Interaction Report

Rifabutin may reduce the blood levels and effects of estradiol. If you are using estradiol for birth control, you may be at increased risk for pregnancy or breakthrough bleeding. You should discuss the use of alternative or additional methods of birth control with your healthcare provider. If you take estradiol for another purpose, such as hormone replacement for menopause, notify your doctor if your medication is no longer controlling your symptoms or you experience abnormal bleeding. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Rifabutin may reduce the blood levels and effects of norethindrone. If you are using norethindrone for birth control, you may be at increased risk for pregnancy or breakthrough bleeding. You should discuss the use of alternative or additional methods of birth control with your healthcare provider. If you take norethindrone for another purpose, such as hormone replacement for menopause, notify your doctor if your medication is no longer controlling your symptoms or you experience abnormal bleeding. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Information for this minor interaction is available on the professional version.

Grapefruit juice may increase the blood levels of certain medications such as norethindrone. You may want to limit your consumption of grapefruit and grapefruit juice during treatment with norethindrone. However, if you have been regularly consuming grapefruit or grapefruit juice with the medication, then it is advisable for you to talk with your doctor before changing the amounts of these products in your diet, as this may alter the effects of your medication. Contact your doctor if your condition changes or you experience increased side effects. Orange juice is not expected to interact.

Information for this minor interaction is available on the professional version.

Information for this minor interaction is available on the professional version.

The use of estrogens is contraindicated in patients with undiagnosed, abnormal vaginal bleeding. Prolonged (> 1 year), unopposed estrogen use (i.e. estrogen without concomitant progestin therapy) has been associated with a significant, dose-related risk of endometrial carcinoma. The risk may be offset substantially by the addition of a progestin but may not be completely abolished. Prior to initiating estrogen therapy, appropriate diagnostic tests should be performed in patients with abnormal vaginal bleeding to rule out endometrial malignancy. The same applies if recurrent or persistent bleeding develops during estrogen therapy.

The use of contraceptives is contraindicated when there is an undiagnosed abnormal genital bleeding. Adequate diagnostic measures should be undertaken to rule out the presence of any malignancy.

When treated with an estrogen, patients with breast cancer and bone metastases may develop severe hypercalcemia, in which case the drug should be stopped and measures be taken to reduce serum calcium levels.

The use of progestogens is considered by manufacturers to be contraindicated in patients with existing or suspected malignancy of the breast. Some supportive data are available for medroxyprogesterone. Specifically, medroxyprogesterone treatment may be associated with breast cancer, primarily when the drug is administered intramuscularly. A pooled analysis of two case-control studies, one from the World Health Organization and the other from New Zealand, revealed a small overall relative risk of breast cancer in women who have ever used intramuscular medroxyprogesterone acetate. The relative risk was higher in the subgroup of women who had initiated therapy within the previous 5 years. Thus, an increased risk (approximately 2-fold) is associated with intramuscular medroxyprogesterone use in the first 5 years. A more recent U.S. study also found a statistically significant increase in breast cancer risk among recent users (defined as last use within the past five years) who used depo-medroxyprogesterone acetate for 12 months or longer.

The use of progestogens, in general, is considered by manufacturers to be contraindicated in patients with active thrombophlebitis, cerebrovascular disease, or a current or past history of thromboembolic disorders. While the role of progestogens in the development of thromboembolic events associated with hormonal therapy is often unclear and thought to be secondary to that of estrogens, it may not be insignificant. Medroxyprogesterone, a common progestational agent, has been shown to produce a hypercoagulable state in high dosages. Whether or not this effect contributes to the development of thrombotic events is unknown. However, thrombophlebitis and pulmonary embolism have been reported with megestrol, an antineoplastic and progestational agent. In addition, an increased risk of nonfatal venous thrombosis has been associated with oral contraceptive combinations containing desogestrel or gestodene relative to those that contain other progestins (e.g., levonorgestrel, norethindrone), suggesting some degree of hemostatic effect by progestogens.

The use of estrogens is considered by manufacturers and some authorities to be contraindicated in patients with active thrombotic, thromboembolic, or thrombophilic disorders. The use of estrogen-containing oral contraceptives is additionally deemed contraindicated in patients with a history of such disorders and/or current cerebrovascular or coronary artery disease. Females with a history of migraines with aura are at an increased risk for stroke and this stroke risk may be further increased in females who have migraines with aura with use of combination oral contraceptives. Hypercoagulability and changes in various clotting factors and blood components have been observed in women receiving estrogen therapy. Known preexisting risk factors for increased thromboembolic or cardiovascular events include smoking, especially over age of 35; hypertension; hyperlipidemia; obesity; diabetes; age over 40; and lupus. Therapy with estrogens should be administered cautiously in the lowest effective dosage and only after careful consideration of risks and benefits. Estrogens should be avoided in patients with a history of thrombotic and thromboembolic disorders associated with estrogen use, except when used in the treatment of metastatic breast or prostatic malignancy.

Clostridioides difficile-associated diarrhea (CDAD), formerly pseudomembranous colitis, has been reported with almost all antibacterial drugs and may range from mild diarrhea to fatal colitis. The most common culprits include clindamycin and lincomycin. Antibacterial therapy alters the normal flora of the colon, leading to overgrowth of C difficile, whose toxins A and B contribute to CDAD development. Morbidity and mortality are increased with hypertoxin-producing strains of C difficile; these infections can be resistant to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea after antibacterial use. Since CDAD has been reported to occur more than 2 months after antibacterial use, careful medical history is necessary. Therapy with broad-spectrum antibacterials and other agents with significant antibacterial activity should be administered cautiously in patients with history of gastrointestinal disease, particularly colitis; pseudomembranous colitis (generally characterized by severe, persistent diarrhea and severe abdominal cramps, and sometimes associated with the passage of blood and mucus), if it occurs, may be more severe in these patients and may be associated with flares in underlying disease activity. Antibacterial drugs not directed against C difficile may need to be stopped if CDAD is suspected or confirmed. Appropriate fluid and electrolyte management, protein supplementation, antibacterial treatment of C difficile, and surgical evaluation should be started as clinically indicated.

The use of oral contraceptives is contraindicated in patients with liver tumors. An increased risk of benign hepatic adenomas and hepatocellular carcinomas has been associated with long-term, oral estrogen- progestin contraceptive use of at least 4 years and 8 years, respectively. Although these tumors are rare and have not been reported with other types of estrogen or progestogen therapies, any preparation containing estrogens and/or progestogens should probably be avoided in patients with existing tumors of the liver. Hepatic hemangiomas and nodular hyperplasia of the liver have been reported with isolated estrogen therapy.

The use of oral contraceptives is contraindicated in patients with liver tumors. An increased risk of benign hepatic adenomas and hepatocellular carcinomas has been associated with long-term, oral estrogen- progestin contraceptive use of at least 4 years and 8 years, respectively. Although these tumors are rare and have not been reported with other types of estrogen or progestogen therapies, any preparation containing estrogens and/or progestogens should probably be avoided in patients with existing tumors of the liver. Hepatic hemangiomas and nodular hyperplasia of the liver have been reported with isolated estrogen therapy.

The use of estrogens is considered by manufacturers and some authorities to be contraindicated in patients with active thrombotic, thromboembolic, or thrombophilic disorders. The use of estrogen-containing oral contraceptives is additionally deemed contraindicated in patients with a history of such disorders and/or current cerebrovascular or coronary artery disease. Females with a history of migraines with aura are at an increased risk for stroke and this stroke risk may be further increased in females who have migraines with aura with use of combination oral contraceptives. Hypercoagulability and changes in various clotting factors and blood components have been observed in women receiving estrogen therapy. Known preexisting risk factors for increased thromboembolic or cardiovascular events include smoking, especially over age of 35; hypertension; hyperlipidemia; obesity; diabetes; age over 40; and lupus. Therapy with estrogens should be administered cautiously in the lowest effective dosage and only after careful consideration of risks and benefits. Estrogens should be avoided in patients with a history of thrombotic and thromboembolic disorders associated with estrogen use, except when used in the treatment of metastatic breast or prostatic malignancy.

The use of progestogens, in general, is considered by manufacturers to be contraindicated in patients with active thrombophlebitis, cerebrovascular disease, or a current or past history of thromboembolic disorders. While the role of progestogens in the development of thromboembolic events associated with hormonal therapy is often unclear and thought to be secondary to that of estrogens, it may not be insignificant. Medroxyprogesterone, a common progestational agent, has been shown to produce a hypercoagulable state in high dosages. Whether or not this effect contributes to the development of thrombotic events is unknown. However, thrombophlebitis and pulmonary embolism have been reported with megestrol, an antineoplastic and progestational agent. In addition, an increased risk of nonfatal venous thrombosis has been associated with oral contraceptive combinations containing desogestrel or gestodene relative to those that contain other progestins (e.g., levonorgestrel, norethindrone), suggesting some degree of hemostatic effect by progestogens.

The risk of myocardial infarction and strokes, including those associated with oral contraceptive use and some estrogen use, is increased in patients with hypertension. Moreover, estrogens (and progestogens) may elevate blood pressure and worsen the hypertension, thus compounding the risk. Clinically significant blood pressure increases have been reported during estrogen therapy, particularly in patients receiving high dosages or treated with oral contraceptive combinations having high progestational activity. These effects also increase with duration of therapy and patient age. Therapy with estrogens should be administered cautiously in patients with preexisting hypertension. Some estrogen-based therapies, such as combined hormonal contraceptives, may be contraindicated in patients with uncontrolled hypertension or hypertension with vascular disease. Patients should be monitored for changes in cardiovascular status, and their antihypertensive regimen adjusted or estrogen therapy withdrawn as necessary. In patients requiring contraception, alternative methods should be considered for those who are hypertensive, over age 35, and smoke.

The use of estrogens is considered by manufacturers and some authorities to be contraindicated in patients with active thrombotic, thromboembolic, or thrombophilic disorders. The use of estrogen-containing oral contraceptives is additionally deemed contraindicated in patients with a history of such disorders and/or current cerebrovascular or coronary artery disease. Females with a history of migraines with aura are at an increased risk for stroke and this stroke risk may be further increased in females who have migraines with aura with use of combination oral contraceptives. Hypercoagulability and changes in various clotting factors and blood components have been observed in women receiving estrogen therapy. Known preexisting risk factors for increased thromboembolic or cardiovascular events include smoking, especially over age of 35; hypertension; hyperlipidemia; obesity; diabetes; age over 40; and lupus. Therapy with estrogens should be administered cautiously in the lowest effective dosage and only after careful consideration of risks and benefits. Estrogens should be avoided in patients with a history of thrombotic and thromboembolic disorders associated with estrogen use, except when used in the treatment of metastatic breast or prostatic malignancy.

The use of progestogens, in general, is contraindicated in patients with impaired hepatic function or liver disease. There are little or no data concerning the pharmacokinetic disposition of the different progestogens in patients with hepatic disease. However, most hormones, including progestational hormones, are known to be extensively metabolized by the liver. Medroxyprogesterone should not be used by women with significant liver disease and should be discontinued if jaundice or disturbances of liver function occur.

The use of estrogens is considered by manufacturers and some authorities to be contraindicated in patients with active thrombotic, thromboembolic, or thrombophilic disorders. The use of estrogen-containing oral contraceptives is additionally deemed contraindicated in patients with a history of such disorders and/or current cerebrovascular or coronary artery disease. Females with a history of migraines with aura are at an increased risk for stroke and this stroke risk may be further increased in females who have migraines with aura with use of combination oral contraceptives. Hypercoagulability and changes in various clotting factors and blood components have been observed in women receiving estrogen therapy. Known preexisting risk factors for increased thromboembolic or cardiovascular events include smoking, especially over age of 35; hypertension; hyperlipidemia; obesity; diabetes; age over 40; and lupus. Therapy with estrogens should be administered cautiously in the lowest effective dosage and only after careful consideration of risks and benefits. Estrogens should be avoided in patients with a history of thrombotic and thromboembolic disorders associated with estrogen use, except when used in the treatment of metastatic breast or prostatic malignancy.

The use of estrogens is generally contraindicated in patients with known or suspected estrogen-dependent neoplasia such as breast and endometrial cancer, since it may stimulate tumor proliferation. High dosages of estrogens may be used for the palliative treatment of inoperable, metastatic breast cancer, but only in appropriately selected men and postmenopausal women.

The use of progestogens, in general, is considered by manufacturers to be contraindicated in patients with active thrombophlebitis, cerebrovascular disease, or a current or past history of thromboembolic disorders. While the role of progestogens in the development of thromboembolic events associated with hormonal therapy is often unclear and thought to be secondary to that of estrogens, it may not be insignificant. Medroxyprogesterone, a common progestational agent, has been shown to produce a hypercoagulable state in high dosages. Whether or not this effect contributes to the development of thrombotic events is unknown. However, thrombophlebitis and pulmonary embolism have been reported with megestrol, an antineoplastic and progestational agent. In addition, an increased risk of nonfatal venous thrombosis has been associated with oral contraceptive combinations containing desogestrel or gestodene relative to those that contain other progestins (e.g., levonorgestrel, norethindrone), suggesting some degree of hemostatic effect by progestogens.

The use of estrogens is considered by manufacturers and some authorities to be contraindicated in patients with active thrombotic, thromboembolic, or thrombophilic disorders. The use of estrogen-containing oral contraceptives is additionally deemed contraindicated in patients with a history of such disorders and/or current cerebrovascular or coronary artery disease. Females with a history of migraines with aura are at an increased risk for stroke and this stroke risk may be further increased in females who have migraines with aura with use of combination oral contraceptives. Hypercoagulability and changes in various clotting factors and blood components have been observed in women receiving estrogen therapy. Known preexisting risk factors for increased thromboembolic or cardiovascular events include smoking, especially over age of 35; hypertension; hyperlipidemia; obesity; diabetes; age over 40; and lupus. Therapy with estrogens should be administered cautiously in the lowest effective dosage and only after careful consideration of risks and benefits. Estrogens should be avoided in patients with a history of thrombotic and thromboembolic disorders associated with estrogen use, except when used in the treatment of metastatic breast or prostatic malignancy.

The use of exogenous estrogens may induce or exacerbate symptoms of angioedema, particularly in women with hereditary angioedema. Close monitoring is recommended when prescribing these agents to patients predisposed to angioedema.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Androgen deprivation therapy may prolong the QT/QTc interval. Health care providers should consider if benefits of therapy outweigh the potential risks in patients with congenital long QT syndrome, congestive heart failure, electrolyte abnormalities, or taking other drugs that can also prolong the QT interval. Consider periodic monitoring of EKG and electrolytes.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

The use of oral contraceptives has been associated with an increased incidence of depression. It is uncertain whether this effect is related to the estrogenic or the progestogenic component of the contraceptive, although excess progesterone activity is associated with depression. Patients with a history of depression receiving estrogen and/or progestogen therapy should be followed closely. The manufacturer of medroxyprogesterone recommends monitoring patients who have a history of depression and to not re- administer medroxyprogesterone if depression recurs.

Impaired glucose tolerance has been observed in some patients administered oral contraceptives and appears to be related primarily to the estrogen dose. However, progestogens can increase insulin secretion and produce insulin resistance to varying degrees, depending on the agent. Caution and close monitoring are recommended in patients with diabetes mellitus during therapy with estrogens and/or progestogens, and adjustments made accordingly in their antidiabetic regimen.

Impaired glucose tolerance has been observed in some patients administered oral contraceptives and appears to be related primarily to the estrogen dose. However, progestogens can increase insulin secretion and produce insulin resistance to varying degrees, depending on the agent. Caution and close monitoring are recommended in patients with diabetes mellitus during therapy with estrogens and/or progestogens, and adjustments made accordingly in their antidiabetic regimen.

Androgen deprivation therapy may prolong the QT/QTc interval. Health care providers should consider if benefits of therapy outweigh the potential risks in patients with congenital long QT syndrome, congestive heart failure, electrolyte abnormalities, or taking other drugs that can also prolong the QT interval. Consider periodic monitoring of EKG and electrolytes.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

A two- to four-fold increase in risk of gallbladder disease has been noted in women receiving postmenopausal estrogen therapy. The risk for gallbladder disease may be less for premenopausal women using oral contraceptives containing low-dose estrogens and/or progestins. Therapy with estrogens should be administered cautiously in patients with preexisting gallbladder disease or a history of pregnancy-related cholestasis.

Some progestogenic agents may elevate plasma LDL levels and/or lower HDL levels, although data have been inconsistent. Patients with preexisting hyperlipidemia may require closer monitoring during progestogen therapy, and adjustments made accordingly in their lipid-lowering regimen.

Estrogens may cause adverse lipid changes. Use of estrogens has been associated with elevations in triglyceride levels, particularly in women with pre-existing hypertriglyceridemia. Discontinue therapy if elevated triglycerides lead to pancreatitis. Manage hypercholesterolemia appropriately as indicated.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens should be used with caution in individuals with severe hypocalcemia or hypoparathyroidism. Estrogen-induced hypocalcemia may occur in patients with hypoparathyroidism; consider whether the benefits of estrogen therapy outweigh the risks.

Estrogens are primarily metabolized by the liver. Use of estrogen therapy is contraindicated in patients with liver dysfunction or disease. Patients with impaired hepatic function may be at increased risk for adverse effects associated with estrogen administration due to decreased drug clearance. Patients with hepatic hemangiomas are at increased risk of exacerbation with use of estrogens. Therapy with estrogens should be administered cautiously in patients with cholestatic jaundice associated with past estrogen use or with pregnancy. In addition, clinicians should be aware that estrogen therapy may affect liver function tests.

The pharmacokinetics of rifabutin are not known in patients with moderate or severe liver dysfunction. No dosage adjustment is necessary for patients with mild liver dysfunction.

Androgen deprivation therapy may prolong the QT/QTc interval. Health care providers should consider if benefits of therapy outweigh the potential risks in patients with congenital long QT syndrome, congestive heart failure, electrolyte abnormalities, or taking other drugs that can also prolong the QT interval. Consider periodic monitoring of EKG and electrolytes.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Rifabutin may be associated with neutropenia, and more rarely thrombocytopenia. Periodic hematologic studies should be considered in patients receiving prophylaxis with rifabutin, especially in patients with preexisting neutropenia and/or thrombocytopenia.

Rifabutin AUC increased by about 71% in patients with severe renal dysfunction (CrCl less than 30 mL/min) compared to patients with CrCl 61 to 74 mL/min. Patients with severe renal dysfunction should be carefully monitored for rifabutin associated adverse reactions; the dosage of rifabutin should be reduced in such patients if toxicity is suspected. No dosage adjustment is necessary for patients with mild or moderate renal dysfunction.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Estrogens and progestogens may cause fluid retention, particularly when given in high dosages or for prolonged periods. Therapy with these agents should be administered cautiously in patients who have preexisting problems with excess fluid. In addition, patients with conditions that may be adversely affected by fluid accumulation, such as asthma, epilepsy, migraine, and cardiovascular or renal dysfunction, should be observed for exacerbation of their condition during estrogen and/or progestogen therapy.

Rifabutin may be associated with neutropenia, and more rarely thrombocytopenia. Periodic hematologic studies should be considered in patients receiving prophylaxis with rifabutin, especially in patients with preexisting neutropenia and/or thrombocytopenia.

When administering estrogen and/or progestogen therapy in patients with thyroid disorders, clinicians should be aware that these hormones may affect thyroid function tests. Changes have mostly been reported with the use of combination oral contraceptives. Specifically, thyroid-binding globulin (TBG) may be increased, resulting in elevated circulating total thyroid hormone, as measured by PBI (protein-bound iodine), T4 by column or radioimmunoassay, or T3 by radioimmunoassay. Free T3 resin uptake may be decreased. On the contrary, a decrease in TBG and, consequently, thyroxine concentration, has been reported by the manufacturers of the progestin-only (norethindrone) oral contraceptives. Patients on thyroid replacement therapy may require higher doses of thyroid hormone and appropriate monitoring.

When administering estrogen and/or progestogen therapy in patients with thyroid disorders, clinicians should be aware that these hormones may affect thyroid function tests. Changes have mostly been reported with the use of combination oral contraceptives. Specifically, thyroid-binding globulin (TBG) may be increased, resulting in elevated circulating total thyroid hormone, as measured by PBI (protein-bound iodine), T4 by column or radioimmunoassay, or T3 by radioimmunoassay. Free T3 resin uptake may be decreased. On the contrary, a decrease in TBG and, consequently, thyroxine concentration, has been reported by the manufacturers of the progestin-only (norethindrone) oral contraceptives. Patients on thyroid replacement therapy may require higher doses of thyroid hormone and appropriate monitoring.

Rifabutin should not be given as monotherapy in patients with active tuberculosis (TB). The administration of rifabutin in the absence of appropriate antituberculosis agents may induce organisms resistant to rifabutin and rifampin. Likewise, patients must not have active TB when receiving rifabutin therapy for Mycobacterium avium complex prophylaxis or other indications where rifabutin might be used alone. Patients who develop symptoms consistent with active TB during rifabutin therapy should be evaluated promptly so that an effective antituberculosis regimen may be instituted if necessary.

Progestogens can cause weight gain, which may be significant (as is the case with parenteral medroxyprogesterone) and undesirable in obese patients attempting to lose weight.