Hi, I was surprised to see all these negative comments, mentioning everything except the answer for the question. Now, I don`t know what is available/unavailable in the questioner`s country, but this forum is to help each other overcome difficulties and I am sure there are solutions to almost everything.
To start I recommend acid-base extraction and using the Cetirizine containing tablets, although I have not done this. (I`ll try to get some similar pills as they are available in almost every country - then attempt the procedure, some pitfalls can only come out with experimenting.)
1. First grind your tablets into a fine powder - e.g. using a coffee grinder
2. Dissolve the powder in distilled water
3. Vacuum filter the insoluble residue (if there is any)
4. I think Cetirizine is soluble in water, but it is also a carboxylic acid. Now carboxylic acids are always soluble in an alkaline solution because they make salts with bases (NaOH, KOH, NaHCO3 etc).
5. I would first do a wash with some non-polar solvent to remove impurities.
6. (Not compulsory, but if your solution is large quantity, then you could reduce the volume by slowly evaporating the water (or vacuum distilling, rotavap whatever you have. This will increase the efficiency of your extraction.)
7. Now basify the solution with 25%NaOH or 33%KOH to at least pH12, you can go a bit over, but don`t use excessive base, it is not a case of `more is better`, it can actually harm your pseudo according to some sources. Some people recommend adding a non-polar solvent (DCM, Chloroform, hexane, petrol ether etc.) first, then add the base, so the basified pseudo will migrate to the non-polar straight away as formed. I would use DCM because then the water will be on top and you can check pH easier in the water phase. Let me know what solvent you have, I can`t imagine country with no solvents available to the public. Go to a DIY or hardware store or just a supermarket and start checking labels. E.g, paint solvents or stain remover solvent (the latter is usually very clean.) DCM can be in paint strippers, if shops don`t sell it to you then check marketplace or other advertising sites.
8. Extract with as much solvent as you can. Do this three times. Ideally the combined solvent should be at least as much as the water left. This increases efficiency tremendously and then you can distill off and save most of the solvent anyway.
9. Combine the solvent from the 3 extractions, wash with some distilled water 2 times 1/4th of the solvent volume is enough. Then finally wash with brine - leave this stand for a while so that brine can suck out as much water from your solvent as possible. Then dry with dry MgSO4, and filter the dryin agent. You should have a relatively clean solution.
10. Distill off your solvent and you should be left with pseudo freebase.
11. Here I would do a TLC to see if there are other components, then you can vacuum filter to clean it or steam distill if you don`t have a strong enough vacuum pump. If you don`t have experience with TLC then you can leave this, your product should be OK for reduction. I will try to do this if I can get some similar tablets and report back.
Let me know if you have any questions then we`ll move on to the next phase to make meth.