Drugs bearing resemblance to codeine in effects due to close structural relationship are variations on the methyl groups at the 3 position including ethylmorphine, also known as codethyline (Dionine), and benzylmorphine (Peronine). While having no narcotic effects of its own, the important opioid precursor thebaine differs from codeine only slightly in structure. Pseudocodeine and some other similar alkaloids not currently used in medicine are found in trace amounts in opium as well. History
Codeine, or 3-methylmorphine, is an alkaloid found in the opium poppy, Papaver somniferum var. album, a plant in the family Papaveraceae. Opium poppy has been cultivated and utilized throughout human history for a variety of medicinal (analgesic, anti-tussive and anti-diarrheal) and hypnotic properties linked to the diversity of its active components, which include morphine, codeine and papaverine. Codeine is found in concentrations of 1% to 3% in opium prepared by the latex method from unripe pods of Papaver somniferum. The name codeine is derived from the Ancient Greek κώδεια (kṓdeia, "poppy head"). The relative proportion of codeine to morphine, the most common opium alkaloid at 4% to 23%, tends to be somewhat higher in the poppy straw method of preparing opium alkaloids.
In the end, if the plasma concentration of the "free met-hemoglobin" and/or "free hemoglobin" is still too high for proximal tubule to absorb back into the body, then hemoglobinuria occurs, indicating an extensive intravascular hemolysis. These remaining free hemoglobin entities also begin to consume nitric oxide, which is critical regulators of vascular homeostasis and basal and stress-mediated smooth muscle relaxation and vasomotor tone, endothelial adhesion molecule expression, and platelet activation and aggregation. The reduction of nitric oxide deeply disturbs the bodys mechanism to maintain the stability of the hemodynamics. Additionally, free hemoglobin manifests direct cytotoxic, inflammatory, and pro-oxidant effects that in turn negatively impact endothelial function. At the meantime, free heme exerts its multiple pro-inflammatory and pro-oxidant effects to the tissues it goes through.It is important to note that although hemosiderins are also included in the urine in the setting of intravascular hemolytic hemoglobinuria, it will be detected only several days after the onset of the extensive intravascular hemolysis and will remain detectable several days after termination of intravascular hemolysis. The phenomenon tells that the detection of hemosiderin in urine is indicative of either ongoing or recent intravascular hemolysis characterized by excessive hemoglobin and/or met-hemoglobin filtered through the renal glomerulus as well as the loss of hemosiderin-laden necrotic tubular cells. See also
Extravascular hemolysis

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