Silly question re: drug potency assay

[chaoticbear]

Trying to settle a discussion between me and one of my doctor friends. We're discussing the "buy on the internet generic Viagra (and other drugs) from India" phenomenon. He's maintaining that it probably doesn't contain any active ingredient anyway. I think that since it's made by Cipla and Ranbaxy and all of the other people who make our generic drugs anyway, there wouldn't be any reason to fake it, $1-2/pill is still plenty for them to make profit on The Real Stuff (TM).

A cursory Google search didn't turn anything up, so I'm turning here for help. I've got a background in chemistry, but don't know enough about sildenafil or designing quantitative analysis techniques to hunt for stuff, and the presence of the excipients only confuses me further.

Assuming I've got a few tablets of imported sildenafil from the Internet that I'm willing to sacrifice in the name of science, how would I go about determining actual drug content? My equipment is fairly limited, I have practically unlimited syringes that could double as sep funnels or burets, glassware that could serve as beakers, and am fairly decent at repurposing things to make something work. I'd be willing to shell out some bucks on some solvents or reagents so long as they'd be reasonably easily obtained.

[mnemosyne]

Not going to happen with the equipment you describe. You'd need an HPLC, ideally. Here's a random paper that describes an assay protocol, though I don't know if it's the one in the USP.


Here's the thing ... if you know the products come from an actually certified generics company (and they are not all based in India!) that has been approved to sell drugs in the United States, then you can be pretty certain that you are getting what you think you are getting - the generic equivalent to brand-name Viagra, and yes, it will be statistically identical in potency, effectiveness, side effects etc.

If the company is not approved by the FDA to sell drugs in the USA, then you might be getting a drug that is statistically identical to Viagra. You might be getting one that is less consistent in manufacturing, say with more variability in dose. You might be getting one with a contaminate from another drug that was made on the same equipment. You may be getting a tablet that's full of excipients and has no drug at all. The only way to tell is, as you say, to test it (which is always a destructive test - you can't test it and use it!)

Even if you ran a drug identification assay on your Internet pills and both shown you have sildenafil and that it's in the indicated concentration, you don't know anything else about how it was made. You don't know if the equipment was clean, if the raw materials are pure, or any of the other details that go into certifying production out of a manufacturing plant. The regulatory agency checks that, and runs audits (and sure, occasionally there are screw-ups, but overall that part of the system is rather good).

[chaoticbear]

I googled it as well and found that at minimum, I'd need an HPLC. And everything you said makes sense, I was just hoping that there was some easy, fun test that would identify it. Like acetonitrile + sildenafil -----> pizza + cookies.

Unfortunately, I don't have any buddies that'd let me borrow their toys for a few hours to test it out. I found a journal article indicating that it's detectable in vitro via spectrophotometry, which would probably be the most affordable way to go about it, but looks like even a used spec-20 is going for nearly $1k on eBay. It'd be worth it to be right and rub it in his face, but not worth that much money.

Re: manufacturing safety, that's not part of the argument between me and him

[Sigene]

spectroscopy wouldn't be as easy as a Spec-20 either. You'd probably need an FT-IR. Plus you would need purification steps and standards for comparison.

I've got some good access to FT-IR and Raman. I'd think Raman on the tablets would be the best, but here again, you would need standard tablets with virtually the same types and levels of exipients to be sure of the presence and concentration of your target analyte

[mnemosyne]

It's been a long time since I worked in the industry, but I seem to recall some work in near-FTIR that could be used both as identification and assay, but even then, you'd need to compare to a standard. Also, this equipment costs a fortune, as does everything else you might want to use! Contract companies (Bodycote maybe, or MDS) could potentially do the work for you, but that would still be very expensive. I've never done a full assay on a pharmaceutical product that required less than about 6 hours of work from start to results (CSI is a lie!!). Of course, for these purposes, you wouldn't have to do a full GMP assay, but it would still take a while.

[chaoticbear]

Well, again, I'm not going for complete analysis. Something approaching "oh, this contains 100mg +/- 25mg sildenafil" would be enough.

Some intensive googling (mostly because I couldn't figure out search terms) turned up a site that will do it quantitatively for $225. It'd almost be worth it, but I'd have to split it with the doctor friend or have him cover it. He's a doctor with no kids, I barely make minimum wage, etc.

[TheBori]

Mnemosyne... "the generic equivalent to brand-name Viagra, and yes, it will be statistically identical in potency, effectiveness, side effects etc. "
In the US, generic drug manufacturers do not have to prove efficacy, just bio-equivalence...the list of ingredients must be the same. The rate of absorption and other pharmaco-kinetic properties can vary widely.

As for testing...take a few and see if you get a 4-hour chubby.

[chaoticbear]

Bioequivalence, at least in the FDA sense, requires that the drugs be absorbed similarly as well. But since there's no generic on the market yet, it means that we'd be relying on the generic company's judgement. (Apparently, though, there are two companies who have already received tentative approval for generic sildenafil, but they of course have to wait for Pfizer's patents to run out). This is fine with me, though, as the ones I have are made by Cipla, who makes other generics approved by the FDA. And there's not really any goofy release mechanism necessary for this particular drug, although I have now found both oral gels and ODT's available on the grey/black market.

And I've taken them before, they certainly work, but could just be the placebo effect at work, right?

Ideally, I'd be able to invite him over for a blinded test, involving restraints and lube. Unfortunately, he lives too far away for that to work.