By X. Topork. Valdosta State University.

Testosterone is metabolized to the more potent 5a-dihydrotestosterone by 5a- reductase buy discount aldactone 100 mg. The 17-substituted testosterone esters (testosterone propionate effective aldactone 25mg, testosterone enanthate generic aldactone 25 mg online, and testosterone cypionate) are administered by injection buy generic aldactone 100 mg line, usually as a depot in oil generic aldactone 100mg line. Absorption of these oral agents is greater if they are administered sublingually, thus avoiding the large hepatic first-pass effect. Nandrolone (Hybolin, Deca-Durabolin) and oxandrolone (Oxandrine, others) are testoster- one derivatives with about a 5- to 10-fold higher anabolic-to-androgenic ratio than testos- terone itself. Androgens form a complex with a specific intracellular receptor (a member of the nu- clear-receptor family) and interact with specific genes to modulate differentiation, develop- ment, and growth. Androgenic actions (1) Androgens stimulate the differentiation and development of Wolffian structures, includ- ing the epididymis, seminal vesicles, prostate, and penis. Anabolic actions (1) Anabolic steroids cause acceleration of epiphyseal closure, and they result in linear growth at puberty. Chapter 10 Drugs Acting on the Endocrine System 231 (2) Anabolic steroids cause an increase in muscle mass and lead to a positive nitrogen balance. Androgens promote linear growth and sexual maturation and maintain male secondary sexual characteristics, libido, and potency. Large doses of androgens increase the extent and rate of muscle for- mation and may increase the intensity of training. Androgens are used to treat hereditary angioedema based on androgen-dependent increases in C1 complement inhibitor. The combination of testosterone or methyltestosterone with estrogens (either esterified estrogens or estradiol) may be used for menopausal hormone therapy when estrogens alone have not provided adequate therapeutic responses. Androgens increase plasma fibrinolytic activity, causing severe bleeding with concomitant anticoagulant therapy. Androgens and anabolic steroids are contraindicated in pregnant women and in patients with carcinoma of the prostate or hepatic, renal, or cardiovascular disease. Antiandrogens are agents that impair the action or synthesis of endogenous androgens. Flutamide is a steroidal oral antiandrogen that acts as a competitive androgen-receptor an- tagonist. Nilutamide and bicalutamide are nonsteroidal androgen-receptor antagonists with better specificity for the androgen receptor and have a longer half-life that permits once-a- day dosing rather than three times a day for finasteride. Ketoconazole is an antifungal agent that blocks multiple P-450–dependent steps in steroidogenesis. Spironolactone antagonizes the binding of both androgen and aldosterone at their respec- tive receptors; it also decreases the activity of the steroidogenic enzyme 17-hydroxylase. Spironolactone is used as a diuretic and to treat hirsutism in women (usually in combina- tion with estrogen). The adrenals also synthesize various androgens, predominantly dehydroepiandrosterone and androstenedione. A wide array of steroid compounds with various ratios of mineralocorticoid to glucocorti- coid properties has been synthesized. Chapter 10 Drugs Acting on the Endocrine System 233 table 10-2 Properties of Adrenocortical Steroids Equivalent Metabolic Anti-Inflammatory Sodium-retaining Agent Dose (mg) Potency Potency Potency Oral Glucocorticoids Cortisol 20 20 1 1 Cortisone 25 20 1 1 Prednisone 5 5 4 0. Cortisone acetate and prednisone are 11-keto steroids that are converted to 11-hydroxyl groups by the liver to give cortisol and prednisolone, respectively. Methylation or hydroxylation at the 16a position abolishes mineralocorticoid activity with little effect on glucocorticoid potency. Natural and synthetic steroids enter cells rapidly and interact with these intracellular receptors. The resulting complexes modulate the transcription rate of specific genes and lead to an increase or decrease in the levels of specific proteins. Both natural and synthetic steroids are excreted by the kidney following reduction and for- mation of glucuronides or sulfates. All of the steroids listed in Table 10-2 (except aldosterone) may be administered orally. Various glucocorticoid preparations are available for otic, rectal, or topi- cal administration. As discussed in Chapter 9, glucocorticoids administered as inhalants are used to treat asthma. Drug administration attempts to pattern the circadian rhythm: A double dose is given in the morning, and a single dose is given in the afternoon. Alternate-day therapy relieves clinical manifestations of the disease state while causing less severe suppression of the adrenal–hypothalamic–pituitary axis.

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Antistreptolysin O anti- bodies are seen with poststreptococcal glomerulonephritis order aldactone 25mg free shipping. This pulmonary-renal syndrome frequently presents with rapidly pro- gressive glomerulonephritis and respiratory failure purchase 25 mg aldactone otc. However 25mg aldactone fast delivery, the constella- tion of findings with sinusitis and glomerulonephritis would not be expected buy aldactone 100 mg without a prescription. Kawasaki disease is an acute multisystem disease that primarily presents in children <5 years of age cheap 100 mg aldactone otc. The clinical manifestations in childhood are nonsuppurative cervical lymphadenitis; desquamation of the fingertips; and erythema of the oral cavity, lips, and palms. Approximately 25% of cases are associated with coronary artery aneurysms that occur late in illness in the convalescent stage. Even if coronary artery aneurysms develop, most regress over the course of the first year if the size is <6 mm. Complications of persistent coronary artery aneurysms include rupture, thrombosis and recanalization, and stenosis at the out- flow area. Dissection of the aortic root and coronary ostia is a common cause of death in Marfan’s syndrome and can also be seen with aortitis due to Takayasu’s arteritis. In this pa- tient, there is no history of hypertension, limb ischemia, or systemic symptoms that would suggest an active vasculitis. In addition, there are no other ischemic symptoms that would be expected in Takayasu’s arteritis. Myocardial bridging overlying a coronary artery is seen frequently at autopsy but is an unusual cause of ischemia. The possibility of cocaine use as a cause of myocardial ischemia in a young individual must be considered, but given the clini- cal history, it is a less likely cause of ischemia in this case. The clas- sic pathway of complement activation is initiated by an antibody-antigen interaction. Active C1 then initiates the cleav- age and concomitant activation of components C4 and C2. The activated C1 is destroyed by a plasma protease inhibitor termed C1 esterase inhibitor. Patients with a deficiency of C1 esterase inhibitor may develop angioedema, sometimes leading to death by asphyxia. In addition to low antigenic or functional levels of C1 esterase inhibitor, patients with this autosomal dominant condition may have normal levels of C1 and C3 but low levels of C4 and C2. Danazol therapy produces a striking increase in the level of this important inhibitor and alleviates the symptoms in many patients. An ac- quired form of angioedema caused by a deficiency of C1 esterase inhibitor has been de- scribed in patients with autoimmune or malignant disease. Commonly affected sites include the cervical and lumbosacral spine, hip, and the knee. In the hands, both the proximal and distal inter- phalangeal joints are frequently affected. Functional asplenism along with easy bruising, neuropathy, and macroglossia suggests amyloidosis. Other findings that argue for amyloidosis are alope- cia, dystrophic nails, and the elevated globulin fraction. The functional asplenism of amy- loidosis is due to direct involvement of the spleen, although hypersplenism may be present. A new diagnosis of sickle cell anemia is unlikely given the patient’s demographic. Cyclical neutro- penia usually occurs in children, although there are also adult forms. X-linked agammaglobulinemia is a rare congenital disorder of males whose B cells do not mature. Patients with this disorder do not make immunoglo- bulins and develop severe upper respiratory infections, often with encapsulated organisms.

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What is the approximate amount of lead necessary to reduce the expo- sure rate from a 200-mCi–99mTc source to less than 5mR/hr at 20cm from the source? If 1% of the primary beam exits through a patient buy 100mg aldactone mastercard, calculate the expo- sure at the midline of the patient order aldactone 25 mg overnight delivery. What are the criteria for the release of patients administered with radiopharmaceutical? Nuclear Medi- cine–Factors Influencing the Choice and Use of Radionuclides Diagnosis and Therapy 25mg aldactone with mastercard. Units and Constants 301 1 nanometer (nm) = 10−9m 1 angstrom (Å) = 10−8cm 1 fermi (F) = 10−13cm 1 inch = 2 order aldactone 100 mg on-line. A process by which the total energy of a radiation is removed by an absorber through which it passes order aldactone 25 mg otc. A machine to accelerate charged particles linearly or in circu- lar paths by means of an electromagnetic field. The accelerated particles such as a-particles, protons, deuterons, and heavy ions possess high ener- gies and can cause nuclear reactions in target atoms by irradiation. A term used to indicate how close a measurement of a quantity is to its true value. A process by which the intensity of radiation is reduced by absorption and/or scattering during its passage through matter. The fraction of g-ray energy attenuated (absorbed plus scattered) per unit length of an absorber (linear attenuation coefficient, m) or per gram of an absorber (mass attenuation coefficient, mm). An electron ejected from an energy shell, instead of a char- acteristic x-ray emission, carrying the energy equal to that of the x-ray minus its binding energy. The number of molecules in 1g·mole of any substance or the number of atoms in 1g·atom of any element. In a nucleus, it is the energy needed to separate a nucleon completely from other nucle- ons in the nucleus. In a chemical bond, it is the energy necessary to sep- arate two binding partners an infinite distance. The time by which one half of an administered dosage of a substance is eliminated by biological processes such as urinary and fecal excretions. A stable element that is added in detectable quantities to a radio- nuclide of the same element, usually to facilitate chemical processing of the radionuclide. The number of photons passing through the collima- tor for each unit of activity present in a source. A component of spatial resolution of an imaging system contributed by the collimator. The dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive mate- rial by an individual during the 50-year period following intake. In this process, a g -ray transfers only a partial amount of energy to an outer orbital electron of an absorber, and the photon itself is deflected with less energy. The probability of occurrence of a nuclear reaction or the formation of a radionuclide in a nuclear reaction. The period of time that a counter remains insensitive to count the next after an event. Dose equivalent at a tissue depth of 1cm (1000mg/cm2) resulting from external whole-body exposure. An instrument to measure the cumulative dose of radiation received during a period of radiation exposure. Time required for an initial administered dose to be reduced to one half as a result of both physical decay and biological elim- ination of a radionuclide. Terms Used in Text is the effective half-life, and Tp and Tb are the physical and biological half- lives, respectively. A mode of decay of a proton-rich radionuclide in which an orbital electron is captured by the nucleus, accompanied by emission of a neutrino and characteristic x-rays or Auger electrons. The kinetic energy gained by an electron when acceler- ated through a potential difference of 1V. Capability of a detecting system to separate two g -ray peaks of different energies. A nuclear process by which a nucleus divides into two nearly equal smaller nuclei, along with the emission of two to three neutrons. A device in which a short-lived daughter is sepa- rated chemically and periodically from a long-lived parent adsorbed on adsorbent material.

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