McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 3 5 Hypothalamic and pituitary agents

■■ BOX 35.3  New delivery system for growth hormone

Prototype summary: Somatropin Indications: Long-term treatment of children with growth failure associated with various deficiencies, girls with Turner’s syndrome, AIDS wasting and cachexia, growth hormone deficiency in adults, and treatment of growth failure in children of small gestational age who do not achieve catch-up growth by 2 years of age. Actions: Replaces human growth hormone; stimulates skeletal growth, growth of internal organs, and protein synthesis. Pharmacokinetics: Route Onset Peak IM, SC Varies 5–7.5 hours T 1/2 : 15 to 50 minutes; metabolised in the liver and excreted in the urine and faeces. Adverse effects: Development of antibodies to growth hormone, insulin resistance, swelling, joint pain, headache, injection-site pain. ■ ■ Assess history of allergy to any GH or binder, presence of closed epiphyses or underlying cranial lesions, serious infection following open-heart surgery, abdominal surgery and pregnancy or breastfeeding status to determine contraindications to the use of the drug . ■ ■ Assess height, weight, thyroid function tests, glucose tolerance tests and GH levels to determine baseline status before beginning therapy and for ■ ■ Reconstitute the drug following manufacturer’s directions because individual products vary ; administer intramuscularly or subcutaneously for appropriate delivery of drug. ■ ■ Monitor response carefully when beginning therapy to allow appropriate dose adjustments as needed. ■ ■ Monitor thyroid function, glucose tolerance and GH levels periodically to monitor endocrine changes and to institute treatment as needed. ■ ■ Provide thorough teaching, including measures to take to avoid adverse effects, warning signs of problems and the need for regular evaluation (including blood tests) to enhance knowledge about any potential adverse effects . Implementation with rationale Care considerations for people receiving drugs affecting growth hormone agonists Assessment: History and examination

Pharmacokinetics Somatropin is injected and reaches peak levels within 7 hours. Box 35.3 discusses a new delivery system for this drug. It is widely distributed in the body and local­ ises in highly perfused tissues, particularly the liver and kidney. Excretion occurs through the urine and faeces. Individuals with liver or renal dysfunction may experi­ ence reduced clearance and increased concentrations of the drug. Contraindications and cautions Somatropin is contraindicated with any known allergy to the drug or ingredients in the drug to avoid hyper- sensitivity reactions . It is also contraindicated in the presence of closed epiphyses or with underlying cranial lesions because of the risk of serious complications , and with abdominal surgery and acute illness second­ ary to complications of open-heart surgery because of potential problems with healing. It should be used with caution in pregnancy and breastfeeding because of the potential for adverse effects on the fetus . Adverse effects The adverse effects that most often occur when using GH include the development of antibodies to GH and subsequent signs of inflammation and autoimmune-type reactions, such as swelling and joint pain, and the endo­ crine reactions of hypothyroidism and insulin resistance. Clinically important drug–drug interactions Caution should be used when these agents are combined with any drugs using the cytochrome P450 liver enzyme system because of a risk for change in metabolism of the combined drugs. Somatropin is a preparation of recombinant DNA– produced human growth hormone that is used to treat children with growth failure due to lack of growth hormone. The drug must be given by injection six or seven times a week. A new delivery form is now available to ease the discomfort and trauma of the frequent injections. The cool.click delivery system is a neon-coloured, needle-free system that delivers the drug through the skin using a fine mist. Tests have shown a bioequivalency of this method with standard injection techniques, and the young people who must use this drug are much less resistant to the dosing. Various drug companies anticipate similar delivery systems, which will provide a therapeutic dose of drugs without the associated discomfort of intramuscular or subcutaneous injection.