methemoglobin, dopamine antagonists, spermidine, chronic fatigue, PD - brief notes

Videos on methemoglobinemia: https://youtu.be/2RFcH_nlR84

Regular pulse oximeter will read normal in cases of methemoglobinemia.

Signs include central cyanosis - blue lips, tongue (as opposed to perhipheral).

Deficiencies in glucose-6-phosphate dehydrogenase or NADH cytochrome b5 reductase (CYB5R ; aka methemoglobin reductase) are risk factors. Excessive nitrite or nitrate consumption can cause MetHb; infants are at higher risk since they produce less CYB5R.

Methemoglobinemia can be a side effect of dopamine antagonists such as metocloparmide (Reglan). Methemoglobinemia from metoclopramide more often occurs in infants, cases in adults are rare but can occur: https://europepmc.org/article/med/10870338

Elevated methemoglobin is among the plasma biomarkers of myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) - as is elevated alpha ketoglutarate:

https://pubmed.ncbi.nlm.nih.gov/30563204/

Interesting abstract:

https://2018.febscongress.org/abstract_preview.aspx?idAbstractEnc=4424170093100097099099424170

"Methemoglobin formation was examined in erythrocytes of 25 patients with Parkinson`s disease (PD) (stage 3–4 by the Hoehn and Yahr scale). The patients receiving levodopa­ containing drugs (madopar, nakom) were also treated with intramuscular injections of mexidol (daily dose 100 mg/day) for 14 days. Control group included 12 clinically healthy persons. 

...

Preincubation of erythrocytes with carnosine followed by acrolein addition prevented the increase in the methemoglobin content, while carnosine had no effect on methemoglobin formation induced by dopamine. Preincubation of erythrocytes with polyamines – spermine and spermidine followed by acrolein and dopamine addition prevented the increase in the methemoglobin content."

 


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