McKenna's Pharmacology for Nursing, 2e

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P A R T 4  Drugs acting on the central and peripheral nervous systems

KEY POINTS

heart rate, increased blood pressure, decreased GI activity and urinary retention. ■■ Levodopa is the standard dopaminergic used to treat parkinsonism and Parkinson’s disease. Several other dopaminergics are now used as adjuncts to levodopa to increase the dopamine effects as long as possible.

■■ Dopaminergic drugs are used to increase the effects of dopamine at receptor sites, restoring the balance of neurotransmitters in the basal ganglia. ■■ The adverse effects associated with these drugs are related to the systemic effects of dopamine, increased

CRITICAL THINKING SCENARIO

Effects of vitamin B 6

intake on levodopa levels

THE SITUATION S.S., a 58-year-old man with well-controlled Parkinson’s disease, presents with severe nausea, anorexia, fainting spells and heart palpitation. He has been maintained on levodopa for the Parkinson’s disease and he claims to have followed his drug regimen religiously. According to S.S. the only change in his lifestyle has been the addition of several health foods and vitamins. His daughter, who recently returned from her first year at university, has begun a new health regimen, including natural foods and plenty of supplemental vitamins. She was so enthusiastic about her new approach that everyone in the family agreed to give this diet a try. CRITICAL THINKING Based on S.S.’s signs and symptoms, what has probably occurred? In Parkinson’s disease, is it possible to differentiate a deterioration of illness from a toxic reaction to a drug? What care implications should be considered when teaching S.S. and his family about the effects of vitamin B 6 on levodopa levels? In what ways can the daughter cope with her role in this crisis? Develop a new care plan for S.S. that involves all family members and that includes drug teaching. DISCUSSION The presenting symptoms reflect an increase in Parkinson’s symptoms, as well as an increase in peripheral dopamine reactions (e.g. palpitations, fainting, anorexia, nausea). It is necessary to determine whether the problem involves a further degeneration in the neurons in the substantia nigra or the particular medication that S.S. has been taking. In many people, responsiveness to levodopa is lost as neural degeneration continues. The explanation of the new lifestyle—full of grains, natural foods and vitamins—alerts the nurse to the possibility of excessive vitamin B 6 intake. In reviewing the vitamin bottles and some of the food packages supplied by S.S., it seems that too much vitamin B 6 , which speeds the

conversion of levodopa to dopamine before it can cross the blood–brain barrier, might be the reason the person’s symptoms recurred. The status of S.S.’s Parkinson’s disease should be evaluated, and then he can be restarted on levodopa. The smallest dose possible should be used initially, with gradual increases to achieve the maximum benefit with the fewest side effects. It would be wise to consider combining the drug with carbidopa to prevent some of S.S.’s recent problems. In addition, S.S. should receive thorough drug teaching in written form for future reference. The need to avoid vitamin B 6 should be emphasised. The entire family should be involved in an explanation of what happened and how this situation can be avoided in the future. Because the daughter may feel guilty about her role, she should have the opportunity to discuss her feelings and explore the positive impact of healthy food on nutrition and quality of life. This situation can serve as a good teaching example for staff, as well as present them with an opportunity to review drug therapy in Parkinson’s disease and the risks and benefits of more extreme diets. Allergies to levodopa; chronic obstructive pulmonary disease (COPD); dysrhythmias, hypotension, hepatic or renal dysfunction; psychoses; peptic ulcer; glaucoma Concurrent use of MAO inhibitors, phenytoin, pyridoxine, papaverine or tricyclic antidepressants (TCAs) Focus physical examination on: CV: blood pressure, pulse rate, peripheral perfusion, electrocardiogram results CNS: orientation, affect, reflexes, grip strength Renal: output, bladder palpation GI: abdominal examination, bowel sounds Respiratory: respiration, adventitious sounds Laboratory tests: renal and liver function tests, full blood count Implementation Ensure safe and appropriate administration of drug. Provide comfort and safety: slow positioning changes; assess orientation, provide pain medication as needed; CARE GUIDE FOR S.S.: LEVODOPA Assessment: History and examination