Talk:Single-phase acid-base DXM extraction

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Theory

Please note that this extraction method is made for dextromethorphan tablets with guaifenesin added. It is not guaranteed to be effective for other compound drugs containing dextromethorphan.

The water solubility of DXM HBr is 25.9mg/ml. It will be converted into DXM freebase at high pH, ​​which is insoluble in water and can produce crystals that are easy to handle.

For other substances in compound drugs, as long as they are guaranteed not to dissolve in water and precipitate at high pH, ​​this method can be used. For example, guaifenesin is insoluble in water, and pharmaceutical excipients will not precipitate at high pH even if they are dissolved in water.

First, we dissolve the tablets in water, let it stand and wait for clarification, take the supernatant, and repeat the process several times. After that, put these supernatants in a container and add alkali solution to it while stirring until no precipitation occurs or the pH is greater than 10. The precipitate should be white and will become granular after standing for about half an hour. Finally, filter through coffee filter paper to obtain a white powder, which is DXM freebase.

Materials

• DXM tablets to be extracted
• Water
• Alkali: I used sodium hydroxide, ammonia should also work.
• Containers: Three or more appropriately sized containers, preferably graduated. A thinner container may help separate the pellet and supernatant.
• Coffee filter paper: To separate the water and DXM freebase, other filters should work.
• Mortar: used to grind the tablets. If you have other ways to grind the tablets, you can also do it.
• Small bottle/plastic bag: used to hold the product.
• pH test paper (optional): used to monitor the pH change of the solution.
• A scale: Scale with at least 0.01g accuracy are needed to correctly weigh substances.

Safety

• If using sodium hydroxide, it will be highly exothermic when dissolved in water. Add it to the liquid in small, frequent additions.
• It should be noted that DXM in freebase form is around 27-37% more potent than its hydrobromide form due to a higher concentration of DXM by weight. One should take this into account when calculating their dose to avoid a potential overdose.
• Please refer to Dosage#Dosage_measurement to correctly weigh the substance.
• If you don’t have an accurate enough scale, Please set the amount you need to take in advance, For example, 300mg DXM HBr requires 20 15mg tablets. I have not tested on such a small batch and cannot guarantee final results.

Preparation

• Grind the drug.
• Calculate the total amount of water needed. Water that can dissolve three times the amount of DXM HBr should be sufficient. More water will allow for more complete extraction, but too much water will make filtration difficult.Too little water at a time will leave too much water trapped in the sediment.
• Prepare the alkali solution. If using sodium hydroxide, dissolve it in small amounts in a small amount of water several times. Prepare enough alkali solution. Using an excess of alkali solution will ensure complete conversion.

If you are processing 1800mg DXM HBr, you will need at least 69.5ml of water(If you could squeeze all the water out of the sediment), but even using 500ml of water will not be a big problem except that filtration will be slower.

Procedure

1. Add the crushed drug to container A and add enough water to dissolve the DXM-HBr. Stir for a while.
2. Let container A sit for a while until the solution separates and the upper layer is more or less clear. Carefully pour the upper layer into container B.
3. Repeat 1 and 2 until no or only a small amount of white precipitate is produced after adding a small amount of alkali solution to a small amount of upper liquid. Generally, most of DXM can be extracted two or three times.
4. (Optional) Filter all the supernatant. However, trace insoluble impurities mixed in usually do not have any negative effects.
5. Add excess lye to container B while stirring. A large amount of white precipitate should be produced. If you have pH paper, you need to make the solution pH greater than 10 to ensure complete extraction.
6. Wait for a while until DXM freebase becomes granular.
7. Filter the liquid in container B with coffee filter paper, and the filtrate enters container C. DXM freebase will remain on the filter paper. If it is difficult to filter, you may not have waited long enough.
8. Add alkali solution to container C. If no white precipitate is produced, it means that the conversion is complete and proceed to the next step. Otherwise, transfer the liquid in container C back to container B and repeat 5, 6, and 7.
9. Rinse DXM freebase with an appropriate amount of water to remove the alkali residue.
10. Transfer DXM freebase on the coffee filter paper to another coffee filter paper and leave it overnight until it dries.
11. Put the product into a small bottle or plastic bag. And label it. And optionally measure the yield.

Other

• DXM freebase has no taste.