A patient with Parkinson's disease has been achieving effective symptom control with levodopa (Dopar) but complains that the symptoms begin to return before it is time for the next dose
"The drug just wears off," he states. The nurse should anticipate that the prescriber will order the patient to
a. take the levodopa at shorter dosing intervals.
b. start taking a drug that reduces levodopa's half-life.
c. take levodopa at longer dosing intervals.
d. increase the dose to increase receptor binding.
ANS: A
Gradual loss (wearing off) develops near the end of the dosing interval and simply indicates that drug levels have declined to a subtherapeutic value. Wearing off can be minimized by shortening the dosing interval.
Giving a drug that prolongs levodopa's plasma half-life and giving a direct-acting dopamine agonist would be effective; giving a drug that reduces levodopa's half-life would not.
Levodopa should be taken at shorter dosing intervals, not longer ones.
Increasing the dose does not increase receptor binding. The availability of receptor binding makes a difference, and as does the drug's affinity for the receptor.
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