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The specific aim of this study is to determine whether water ingestion potentiates the pressor response to pseudoephedrine in patients with primary disorders of autonomic failure. The study design will enable us to also evaluate the pressor response to water alone and to pseudoephedrine alone. In a secondary analysis, we will compare the results in patients with two autonomic disorders, pure autonomic failure (PAF) and multiple system atrophy (MSA). We hypothesize that drinking water following a dose of pseudoephedrine will lead to a greater increase in blood pressure than pseudoephedrine alone.
Full description
The maximal pressor response to water is reached when other pressor agents are only beginning to act. In addition to the therapeutic value of water ingestion alone, the blood pressure-raising effects of agents that increase sympathetic nervous system tone, such as phenylpropanolamine, are potentiated by water drinking. These drug interaction effects can be exploited in the treatment of orthostatic hypotension with the combination of water and a sympathomimetic potentially able to increase blood pressure to a greater extent and for a longer period of time than either water or the medication alone. However, the interaction can also lead to potentially dangerous blood pressure surges.
This protocol requires an initial screening history and physical of study participants, including safety labs and EKGs, and evaluation of their autonomic nervous system status following the consent process. If the patient meets study criteria and is willing to undergo study testing, the 4-way crossover protocol will follow.
Study Testing days 1 and 2 Arm 1: Pseudoephedrine 30 mg PO + 50 ml water Arm 2: Pseudoephedrine 30 mg PO + 480 ml water
Study Testing days 3 and 4 are optional Arm 3: Placebo PO + 50 ml water Arm 4: Placebo PO + 480 ml water Testing will be performed according to the same schedule as for Arms 1 and 2. Instrumentation will be limited to the Dinamap electrocardiographic and blood pressure (brachial cuff) recorder set up for measurements every 5 minutes throughout the study for Arms 3 and 4.
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35 participants in 4 patient groups, including a placebo group
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Data sourced from clinicaltrials.gov
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