Hector Warnes: Pyridoxine in the treatment of lithium-induced tremor
Hector Warnes’ Reply to Samuel Gershon’s and Janusz Rybakowski’s comments
I fully agree that tremors are recently seen in patients on lithium treatment and are mostly related to the blood levels achieved as determined to reach the therapeutic window between 0.5 mmol/L to 1.2 mmol/L. The tremors started at a lower level of 0.6. I thought of three possibilities: one is that the laboratory results were wrong; the second is that drug interactions confounded the findings; the third is that the patient had a specific sensibility to lithium. I have seen many cases of aripiprazole therapy that developed akathisia on low doses to the point that patients refused to take the drug while others did not have that side effect even on higher doses.
Propranolol has been the drug of choice to treat lithium induced tremors However, I did not use it, not only because it might worsen the patient’s depressive state (being a beta-adrenergic blocking agent but also because the patient had already experienced several hypotensive crisis (100/60) which caused him to lose stability or at times to faint.
I attributed it to the antihypertensive and diuretic he was given by the cardiologist besides the fact that he lost considerable weight and had no appetite at the zenith of his depressive cycle. I did not increase the doses of Pyridoxine because of its potential side effect particularly on doses over 500 mg.
While the patient was taking Pyridoxine he also complained of tingling sleepiness and headaches.
When in doubt, as most doctors do I send the patients’ lab work to two laboratories in order to monitor the plasma drug levels. It is amazing that I rarely get the exact result from both. Recently, from one lab the results of lithium levels was 1.2 mmol/L and from another on the same day it was 6.6 mmol/L.
Professor Rybakowski’s observation on the frequency of the lithium induced tremors (in neurophysiological terms measured by the number of tremors per seconds) as compared with the patient with Parkinsonian tremors is quite important. A clinical observation which may be overlooked is the differential diagnoses and implications of essential tremors and unilateral tremors. We used to observe that patients had a fine tremor or coarse tremor but did not clarify the amplitude nor the frequency per second or per minute. Another important distinction is between an intentional tremor (seen only when the patient wants to write or to clean the dishes for example) and a continuous tremor.
Heinrich Rudolf Hertz (1857-1894) was able to measure the frequency of waves occurring each second (e.g., delta waves 11/2 - 2 waves per second). The electromagnetic waves are repetitive every second at the same frequency. The amplitude of the wave is measured in microV and indicates the electromagnetic tension.
March 25, 2021