3-O-Methyldopa and the response to levodopa in Parkinson's disease

Authors

  • Dr. John G. Nutt MD,

    Corresponding author
    1. Department of Neurology, Orgeon Health Sciences University, 3181 Southwest Sam Jackson Park Rd, Portland, OR 97201
    • Department of Neurology, Orgeon Health Sciences University, 3181 Southwest Sam Jackson Park Rd, Portland, OR 97201
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  • William R. Woodward PhD,

    1. Department of Neurology, Orgeon Health Sciences University, 3181 Southwest Sam Jackson Park Rd, Portland, OR 97201
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  • Stephen T. Gancher MD,

    1. Department of Neurology, Orgeon Health Sciences University, 3181 Southwest Sam Jackson Park Rd, Portland, OR 97201
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  • Dawn Merrick BS

    1. Department of Neurology, Orgeon Health Sciences University, 3181 Southwest Sam Jackson Park Rd, Portland, OR 97201
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Abstract

Plasma 3-O-methyldopa (3OMD) concentrations in parkinsonian patients treated with levodopa on a long-term basis reflect daily levodopa dosage and do not vary markedly during the day. Oral challenges with 3OMD reduce the clinical response to levodopa infusions, but 3OMD is no more potent than phenylalanine in this regard. These observations, plus the fact that 3OMD makes a small contribution to the total concentration of large neutral amino acids competing with levodopa for transport at the blood--brain barrier, support the contention that 3OMD is not an important determinant of clinical response to levodopa.

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