McKenna's Pharmacology for Nursing, 2e

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P A R T 6  Drugs acting on the endocrine system

Adverse effects Adverse effects associated with these drugs are related to the stimulation or blocking of regular hormone control. Agonists can lead to increased cortisol and aldosterone levels, causing fluid retention, electro­ lyte imbalance, impaired healing and elevated glucose levels, or to increased release of sex hormones, leading to ovarian overstimulation, flushing, increased tem­ perature and appetite and fluid retention. Antagonists can lead to a decrease in testosterone levels, leading to loss of energy, decreased sperm count and activity and potential alterations in secondary sex characteristics, or to a decrease in female sex hormones, leading to lack of menstruation, fluid and electrolyte changes, insomnia and irritability. Prototype summary: Leuprorelin Indications: Treatment of advanced prostatic cancer, endometriosis, uterine leiomyomata. Actions: LHRH agonist that occupies pituitary gonadotropin-releasing hormone receptors and desensitises them; causes an initial increase and then profound decrease in LH and FSH levels. Pharmacokinetics: Route Onset Peak Duration IM depot 4 hours Variable 1, 2, 3 or 4 months T 1/2 : 3 hours; metabolism and excretion are unknown. Adverse effects: Dizziness, headache, pain, peripheral oedema, myocardial infarction, nausea, vomiting, anorexia, constipation, urinary frequency, haematuria, hot flushes, increased sweating.

these hormones have not been clearly identified. Not all of the hypothalamic hormones are used as phar­ macological agents. A number of the hypothalamic releasing hormones described here are used for diag­ nostic purposes only, and others are used primarily as antineoplastic agents. Agonists CRH stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary and is used to diagnose Cushing’s disease (a condition char­ acterised by hypersecretion of adrenocortical hormones in response to excessive ACTH release). Goserelin is an analogue of GnRH. Following an initial burst of follicle- stimulating hormone (FSH) and luteinising hormone (LH) release, this drug inhibits pituitary gonadotropin secretion, with a resultant drop in the production of the sex hormones. See Table 35.1 for usual indications for each of these agents. Antagonists Cetrorelix, ganirelix, leuprorelin and nafarelin are antagonists of GnRH. Leuprorelin occupies pituitary GnRH receptor sites so that they no longer respond to GnRH; as a result, there is no stimulation for release of LH and FSH. Nafarelin, a potent agonist of GnRH, is used to decrease the production of gonadal hormones through repeated stimulation of their receptor sites. After about 4 weeks of therapy, gonadal hormone levels fall, and the cells they normally stimulate are quiet. See Table 35.1 for usual indications for each of these agents. Pharmacokinetics For the most part, these drugs are absorbed slowly when given intramuscularly (IM), subcutaneously (SC) or in depot form. Nafarelin is given in a nasal form. They tend to have very long half-lives of days to weeks. Metabolism is not understood, but it is thought that they are meta­ bolised by endogenous hormonal pathways. Because they are hormones or similar to hormones, they cross the placenta and cross into breast milk. Most of them are excreted in the urine. Contraindications and cautions These drugs are contraindicated with known hyper­ sensitivity to any component of the drug because of the risk of hypersensitivity reactions , and during pregnancy and breastfeeding because of the potential adverse effects to the fetus or baby. Caution should be used with renal impairment, which could interfere with excretion of the drug ; with peripheral vascular disorders, which could alter the absorption of injected drug ; and with rhinitis when using nafarelin, which could alter the absorption of the nasal spray.

Care considerations for people receiving drugs affecting hypothalamic hormones

The specific care of the person who is receiving a hypothalamic releasing factor is related to the hormone (or hormones) that the drug is affecting (see Chapter 36 for adrenocorticoid hormones and Chapters 40 and 41 for sex hormones). Drugs used for diagnostic purposes are short lived; information about these agents should be included in any teaching about the diagnostic procedure. Guidelines for other agents can be found with the therapeutic drug class to which they belong (e.g. antineoplastic agents, Chapter 14).