Now that Canadian veterinarians can legally import antiviral drugs for treatment of feline infectious peritonitis (FIP), there’s no (good) reason for people in Canada to be sourcing these drugs on the black market. However, there are still many countries (e.g. the US) where it’s still tough or impossible to get these drugs legally, so the black market for them will likely continue to thrive. That’s a problem for many reasons, one of which is the highly questionable quality of black market drugs, and a recently published study (Kent et al. J Am Vet Med Assoc 2024) highlights that particular concern.

The researchers collected leftover drugs from people who had purchased FIP antiviral drugs on the black market to treat their cats. They ended up with 127 drug samples. The results were not surprising, but not good.

Black market injectable remdesivir and GS-441524:

• 95% of samples contained more drug than the label stated – on average 39% more.
• Only 2/87 products were within 95-105% of the stated concentration, the range that is required for licensed drugs produced under Good Manufacturing Practices (GMPs).
• The average pH of the drugs was 1.3 – that’s really acidic. The acidity is needed to keep the drug in solution, but it shows why injection site problems are so common.

Black market oral GS-441524:

• These samples were all over the board. Fourty-three percent (43%) contained more drug than stated on the label (on average 75% more), and 58% contained less durg that stated on the label (on average 39% less). One product contained only 18% of the amount of drug that was stated on the label.
• Only 3/40 samples were within the 95-105% range of the stated concentration.

One injectable and two oral products that were supposed to be GS-441524 were actually remdesivir.

Even interpreting the labels on these samples was a challenge. As black market products, there’s no requirement for any standard (or accurate) labeling. The paper mentions that “It is known within the FIP treatment community that producers report the strength of the pills based on what is thought to be bioavailable to the cat. Therefore, the strength of the pill expressed on the label reflects the producer’s estimation of the equivalent SC dose. This is presumably done to make the process of switching between injectable and oral formulations easier for lay owners.”

• Some labels stated the amount of drug that was (supposed to be) there, while some basically said “we put in X amount but expect only part of it to absorbed by the cat, so we’ll estimate that it actually means Y amount” …presumably with no real data to back up their estimate.

So, it’s possible the products contained more drug that they indicated based on the assumption of lower bioavailability (less drug making it into the cat’s system after it’s given orally). However, that doesn’t account for the more than 50% of samples containing less drug than stated on the label. The fact that the authors had to make various guesses makes some of the percentage calculations debatable (that’s not a criticism, there’s really no good way to do it), and highlights challenges for cat owners who order the drug and treat their cats themselves. If these researchers struggled to guess how much drug should have been there, what can the average cat owner discern?

They also tested a product that said it was something else, but which is known to actually be GS-441524 (Xraphconn). The labels said the tablets were 50 or 100 mg of “MT-0901,” but they were, as expected, GS-441524, with 18 or 47 mg per tablet, respectively. This highlights yet another black market “buyer beware” issue.

A quote from the paper highlights even more concerns with these drugs: “Due to the unlicensed nature of this industry, packages misrepresenting the contents and intended use of these GS-441524 products are common. Products are shipped in boxes labeled as facial masks, serums, or cat nutrients, possibly to curb suspicion during shipment.  Additionally, some products are marketed vaguely as FIP cures with active ingredients other than GS-441524. For example, the brand OM markets their products as containing 50 mg of sea sponge extract, and Mutian products are advertised to also contain vitamin B12. Mutian lists its active ingredient as MT-0901 and is described by the company as an adenosine nucleside analogue. While the LC-MS/MS technique used here was unable to determine whether sea sponge extract, B12, or any other adenosine nucleoside analogues were present in the samples, all 127 samples did contain GS-441524.“

So what do we need?

In countries where effective FIP drugs are legally available, we need to use those drugs.

• Approved products manufactured by reputable companies are made with strict quality control and testing practices, which gives us confidence that the products contain the drug that is supposed to be there at very close to the stated concentration.
• Black market drugs and drugs compounded from non-pharmaceutical grade compounds do not provide the same level of assurance, so there is more risk.
• In Canada, there’s absolutely no reason anymore to use black market drugs or otherwise formulated drugs not from a reputable company with robust quality control practices.

In countries where effective FIP drugs aren’t legally available, legal access needs to be facilitated.

• These drugs save cats’ lives, and there’s no downside to allowing legal importation. It’s otherwise occurring illegally, and it’s far better for cats, owners and veterinarians to have access them under a controlled process where product quality can be assured.