McKenna's Pharmacology for Nursing, 2e

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P A R T 6  Drugs acting on the endocrine system

TABLE 35.2

DRUGS IN FOCUS Drug affecting anterior pituitary hormones (continued)

Drug name

Dosage/route

Usual indications

Drugs affecting other anterior pituitary hormones cabergoline (Bergoline) 2–3 mg PO daily

Treatment of signs and symptoms of Parkinson’s disease Treatment of male hypogonadism, to induce ovulation in females with functioning ovaries, for treatment of prepubertal cryptorchidism when there is no anatomical obstruction to testicular movement Induction of ovulation in infertile females who have been pretreated with FSH

chorionic gonadotropin (Pregnyl)

Dose varies with indication; 4000–10,000 International Units IM one to three times per week is not unusual

choriogonadotropin alfa (Ovidrel) quinagolide (Norprolac)

250 mcg SC given 1 day after last dose of a follicle-stimulating hormone (FSH) stimulator 25 mcg/day PO for 3 days, then 50 mcg/day for further 3 days then 75–125 mcg/day PO 0.9 mg IM, followed by 0.9 mg IM in 24 hours

Treatment of hyperprolactinaemia

thyrotropin alfa (Thyrogen)

Adjunctive treatment for post-radioiodine ablation of thyroid tissue in people with near-total thyroidectomy and well- differentiated thyroid cancer without metastasis

deficiency before any other signs and symptoms occur. Hypopituitarism may occur as a result of developmen­ tal abnormalities or congenital defects of the pituitary, circulatory disturbances (e.g. haemorrhage, infarction), acute or chronic inflammation of the pituitary and pituitary tumours. GH deficiency in children results in short stature ( dwarfism ). Adults with somatropin deficiency syndrome (SDS) may have hypopituitarism as a result of pituitary tumours or trauma, or they may have been treated for GH deficiency as children, resulting in a shutdown of the pituitary production of somatotropin. GH deficiency was once treated with GH injections extracted from the pituitary glands of cadavers. The supply of GH was therefore rather limited and costly (Box 35.2). Synthetic human GH is now available from recombinant DNA sources, using genetic engineering. Synthetic GH is expensive, but it is thought to be safer than cadaver GH and is being used increasingly to treat GH deficiencies. Somatropin ( Genotropin , Omnitrope , Saizen and others) and somatropin recombinant DNA (rDNA) origin ( Zomacton ) are used for GH replacement today. Therapeutic actions and indications In clinical practice, the agents that are used purely as a replacement for anterior pituitary hormones are those acting as GH—somatropin and somatropin rDNA origin. Both of these drugs are produced with the use of recombinant DNA technology. See Table 35.2 for indications.

■■ BOX 35.2  Growth hormone therapy

In the past, growth hormone (GH) therapy was expensive and unsafe. The use of cadaver pituitaries resulted in unreliable hormone levels and, in many cases, hypersensitivity reactions to the proteins found in the drug. With the advent of genetic engineering and the development of safer, more reliable forms of growth hormone, there has been a surge in the use of the drug to treat children with short stature. Even so, the drug is still costly and not without adverse effects. Growth hormone can be used to treat growth failure caused either by lack of growth hormone or by renal failure. It also can help children with normal growth hormone levels who are just genetically small. Before the drug is prescribed, the child must undergo screening procedures and specific testing (including radiographs and blood tests) and must display a willingness to have regular injections. The child taking this drug will need to have pretherapy and periodic tests of thyroid function, blood glucose levels, glucose tolerance tests, and tests for growth hormone antibodies (a risk that increases with the length of therapy). In addition, radiographs of the long bones will be taken to monitor for closure of the epiphyses, a sign that the drug must be stopped. Because the child who is taking growth hormone may experience sudden growth, they will need to be monitored for nutritional needs, as well as psychological trauma that may occur with the sudden change in body image. Insulin therapy and replacement thyroid therapy may be needed, depending on the child’s response to the drug. (See also Focus on safe medication administration related to growth hormone therapy.)