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I am conducting research for a new drug that contains powdered sodium bicarbonate, and the drug will need to be sterilized after placement into it's container/closure system. Typically, this is performed with steam, at 122.5 °C for 15 minutes, but in the case of sodium bicarbonate, this would cause decomposition:

$$\ce{2 NaHCO3 → Na2CO3 + H2O + CO2}$$

The alternative is to sterilize with ionizing (gamma) radiation. Will this also cause decomposition? Any help or referral to another authority is much appreciated.

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    $\begingroup$ You may already be aware, but the term you're looking for is "radiolysis". A cursory Google search shows some results for bicarbonate radiolysis, but I haven't parsed anything. My instinct is that while it could theoretically cause some decomposition, almost all of the bicarbonate will remain intact in any reasonable sterilising gamma flux. Living matter is far more fragile than an inorganic salt. $\endgroup$ – Nicolau Saker Neto Dec 4 '18 at 9:14
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    $\begingroup$ Long story short, don't worry: the drug will decompose way sooner than bicarbonate. $\endgroup$ – Ivan Neretin Jan 29 at 13:13
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There is an equilibrium between decomposition and recombination, i.e. as $\ce{CO2}$ is given off, it joins back to the $\ce{Na2CO3}$ to form $\ce{NaHCO3}$.

$\ce{2NaHCO3 <-->Na2CO3 + CO2}$

So for moderate doses, given at moderate rates, it's unlikely great pressure would develop, but you'd need to test to see if the drug is degraded by decomposition products.

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The likely issue is the presence of any water (which can also be sourced as you noted by the heating of NaHCO3).

Here is a source to quote:

The radiolysis of water due to ionizing radiation results in the production of electrons, H● atoms, ●OH radicals, H3O+ ions and molecules (dihydrogen H2 and hydrogen peroxide H2O2).

The formation of any of such radicals would likely degrade your new drug.

So, does your irradiation, seemingly result in any visible signs of water? If yes, a possible quality issue.

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  • $\begingroup$ The drug is lidocaine (an injectable weak acid aqueous solution), and will be kept in a separate compartment from the bicarb powder until just prior to injection. I expect we would find some trace water in the bicarb just from being in the filling hopper. $\endgroup$ – JSK28031 Jan 30 at 15:55

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