Sodium bicarbonate Pseudoephedrine

In a study with human subjects, whose urine pH was controlled with sodium bicarbonate and ammonium chloride, it was found that 10-25% of the administered pseudoephedrine hydrochloride was metabolized to norpseudoephedrine and the elimination of pseudoephedrine and norpseudoephedrine was related to urine pH. As the urine pH increased, the serum half-life of pseudoephedrine and norpseudoephedrine increased.15 In another similar study it was found that a decrease... 

An ultraviolet spectrophotometric method based on the absorbance of a periodate oxidation product of pseudoephedrine hydrochloride will be the official method of analysis in the USP XX.19,20 A portion of tablets or syrup in water is placed in a separatory funnel. Sodium bicarbonate and sodium metaperiodate are added. After standing for 15 minutes, 1 N HC1 is added. The solution is extracted with hexane. The hexane extract is filtered and its absorbance determined at 242 nm in 1 cm cells. The amount of the oxidation product of pseudoephedrine hydrochloride is determined by comparison of the sample absorbance against the absorbance of a Pseudoephedrine Hydrochloride Reference Standard treated in the same manner. 

A. (1 S,2S)-N-(2-Hydroxy-1 -methyl-2-phenylethyl)-N-methylpropionamide, ((1S,2S)-pseudoephedrinepropionamide). A flame-dried, 1-L, round-bottomed flask equipped with a Teflon-coated magnetic stirring bar is charged with 21.3 g (129 mmol) of (1S,2S)-(+)-pseudoephedrine (Note 1) and 250 mL of tetrahydrofuran (Note 2). The flask is placed in a water bath at 23°C, and to the well-stirred solution, 18.0 g (138 mmol) of propionic anhydride (Note 3) is added by a Pasteur pipette in 1-mL portions over approximately 5 min. The flask is sealed with a rubber septum containing a needle adapter to an argon-filled balloon, and the clear, colorless solution is allowed to stir at 23°C for an additional 10 min. The rubber septum is removed, and the reaction solution is neutralized by the addition of 400 mL of saturated aqueous sodium bicarbonate solution. After thorough mixing (Note 4), the biphasic mixture is poured... 

The pH of the aqueous phase following the addition of sodium bicarbonate is approximately 4. If the pH is less than 4, additional sodium bicarbonate should be added until the pH is 4 or slightly above. Small amounts of the pseudoephedrine aminal remain at this point, but are hydrolyzed during the rotary evaporation step. 

SYMPATHOMIMETICS ANTACIDS-SODIUM BICARBONATE Possibly t ephedrine/ pseudoephedrine levels Alkalinising urine 1 excretion of these sympathomimetics Watch for early features of toxicity... 

Aluminium hydroxide may possibly cause a more rapid onset of pseudoephedrine activity (but this needs confirmation). Any interaction seems unlikely to be clinically significant. Similarly, the effects of kaolin on absorption are small and unlikely to be clinically important. For the effect of sodium bicarbonate on pseudoephedrine and ephedrine, see urinary alka-Iinisers%(p.l277). 

Alkalinisation of the urine (e.g. by sodium bicarbonate) causes retention of ephedrine and pseudoephedrine by the kidneys, leading to the possible development of toxicity (tremors, anxiety, insomnia, tachycardia). Acidification of the urine (e.g. with ammonium chloride) has the opposite effect. 

This confirms an earlier study, in which it was found that at a urinary pH of 8, the half-life of pseudoephedrine was 16, 9.2, and 15 hours in 3 subjects, respectively. At a urinary pH of about 5, the half-life was 4.8,3, and 6.4 hours, respectively. Sodium bicarbonate was given to raise urinary pH and ammonium chloride to lower urinary pH. 

Another study in 6 healthy subjects found that sodium bicarbonate 5 g initially increased the excretion rate of a single 60-mg dose of pseudoephedrine, but as the urinary pH increased the excretion of pseudoephedrine was reduced. ... 

The increased rate of absorption of pseudoephedrine seen with sodium bicarbonate is probably also due to pH rises, which favour the formation of the lipid-soluble absorbable form of pseudoephedrine. 

The interaction between ephedrine or pseudoephedrine and urinary alkalinisers are established but reports of adverse reactions in patients appear to be rare. Be aware that any increase in the adverse effects of these drugs (tremor, anxiety, insomnia, tachycardia, etc.) could be due to drug retention brought about by this interaction. Acetazolamide makes the urine alkaline and would be expected to interact with ephedrine and pseudoephedrine in the same way as sodium bicarbonate. 

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