McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 2 4 Antiparkinsonism agents

The combination of levodopa with vitamin B 6 or with phenytoin may lead to decreased efficacy of the levodopa (see Critical thinking scenario). Reduced effect­ iveness of both drugs may also result if dopaminergics are combined with dopamine antagonists. In addition, people who take dopaminergics should be cautioned to avoid over-the-counter vitamins; if such medications are used, the person should be monitored closely because a decrease in dopaminergic effectiveness can result.

■ ■ Monitor the results of laboratory tests, such as liver and renal function studies, to determine need for possible dose adjustment , and full blood count (FBC) with differential to evaluate for possible bone marrow suppression. Implementation with rationale ■ ■ Arrange to decrease the dose of the drug if therapy has been interrupted for any reason to prevent systemic dopaminergic effects. ■ ■ Evaluate disease progress and signs and symptoms periodically and record for reference of disease progress and drug response. ■ ■ Give the drug with meals to alleviate GI irritation if GI upset is a problem. ■ ■ Monitor bowel function and institute a bowel program if constipation is severe. ■ ■ Ensure that the person voids before taking the drug if urinary retention is a problem. ■ ■ Monitor urinary output, palpate bladder and check for residual urine if urinary retention becomes a problem. ■ ■ Establish safety precautions if CNS or vision changes occur to prevent injury. ■ ■ Monitor hepatic, renal and haematological tests periodically during therapy to detect early signs of dysfunction and consider re-evaluation of drug therapy. ■ ■ Provide support services and comfort measures as needed to improve compliance. ■ ■ Provide thorough teaching about topics such as the drug name and prescribed dose, measures to help avoid adverse effects, warning signs that may indicate problems, and the need for periodic monitoring and evaluation to enhance knowledge about drug therapy and to promote compliance. ■ ■ Offer support and encouragement to help the person cope with the disease and drug regimen. Evaluation ■ ■ Monitor response to the drug (improvement in signs and symptoms of Parkinson’s disease). ■ ■ Monitor for adverse effects (CNS changes, urinary retention, GI depression, tachycardia, increased sweating, flushing). ■ ■ Evaluate the effectiveness of the teaching plan (person can give the drug name and dosage, name possible adverse effects to watch for and specific measures to prevent them and discuss the importance of continued follow-up). ■ ■ Monitor the effectiveness of support measures and compliance with the regimen.

Care considerations for people receiving dopaminergic agents

Assessment: History and examination

■ ■ Assess for contraindications or cautions: any known allergies to these drugs t o avoid hypersensitivity reactions ; GI depression or obstruction, urinary hesitancy or obstruction, benign prostatic hypertrophy or glaucoma, which may be exacerbated by these drugs ; cardiac arrhythmias, hypertension or respiratory disease, which may be exacerbated by dopamine receptor stimulation ; current status of pregnancy or breastfeeding, which are cautions or contraindications to use of the drug ; and renal or hepatic dysfunction, which could interfere with the drug’s excretion or metabolism. ■ ■ Perform a physical assessment to determine baseline status before beginning therapy, to determine the effectiveness of drug therapy and to monitor for any potential adverse effects. ■ ■ Inspect the skin for evidence of skin lesions or history of melanoma if the person is to receive levodopa, which could cause or exacerbate melanoma . ■ ■ Assess for a history of prolonged QT interval and obtain an electrocardiogram if apomorphine is to be administered to avoid further prolonged QT interval and serious arrhythmias . ■ ■ Assess level of orientation and neurological status, including affect, reflexes, bilateral grip strength, gait, tremors and spasticity, to evaluate any CNS effects. ■ ■ Auscultate lungs and assess respiratory status to evaluate for changes that could be exacerbated by the drug’s effect. ■ ■ Monitor pulse, blood pressure and cardiac output to evaluate for possible adverse effects. ■ ■ Auscultate bowel sounds to evaluate GI motility to assess for adverse effects. ■ ■ Assess urine output and palpate bladder to determine adequate bladder and renal function.