Chloroquine Phosphate - Fish Medication Information


Dr. Fish
20 Mar 2019
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Chloroquine Phosphate *** The information contained here is subject to changes as I experiment and learn more about Chloroquine Phosphate ***

What It TreatsMarine Ich (Cryptocaryon irritans), Marine Velvet Disease (Amyloodinium ocellatum), Brooklynella hostilis and Uronema marinum.

How To Buy – Chloroquine phosphate (CP) is an antimalarial drug for humans which also treats external parasites that afflict marine fish (and possibly freshwater fish as well.) However, there are a few challenges to overcome with CP. The very first is obtaining it because a prescription is usually required to buy pharmaceutical-grade CP. While pharmaceutical-grade is not an absolute requirement, the closer the medication is to being 99% pure the more effective it is. Many CP failures can be traced back to buying the medication on eBay or from some other unknown source. The best strategy for obtaining CP is to ask your local veterinarian for a prescription which can then be filled by a compounding pharmacy:

A backup plan is to buy from this source, which has tested 94-96% pure for me (although I cannot guarantee every batch from this source will test the same):

Sometimes CP is dispensed in tablet form instead of powder. The tablets are fine to use, but the downside is you get less "chloroquine base" out of them so you must dose more. The following was taken from Bob Goemans online book, THE LIVING AQUARIUM MANUAL:
In most cases, 250 mg tablets have an equivalence of 150 mg chloroquine base, and 500 mg tablets have an equivalence of 300 mg chloroquine base. Although the purity mentioned above is generally accurate, it would be best to verify the chloroquine base contained in the tablets of your choice in order to be able to properly calculate the exact dosage. Keep in mind if you decide to use the tablets, there are some inactive ingredients, which you may have to deal with, e.g., Camauba Wax, Colloidal Silicon Dioxide, Dibasic Calcium Phosphate, Hydroxypropyl Methylcellulose, Magnesium Stearate, Microcrystalline Cellulose, Polyethylene Glycol, Polysorbate 80, Pregelatinized Starch, Sodium Starch Glycolate, Stearic Acid, and Titanium Dioxide. And as mentioned earlier in this chapter there are occasions where some medicines are not in their pure form (100% pure), i.e., mixed with a substance called a 'carrier,' which should be noted on its label. If so its potency is reduced, and if not sure about the exact amount of medication needed, suggest contacting a more experienced aquarist for the way to resolve this situation.
How To Dose – In most cases CP is dispensed in powder form, and a digital scale is needed to accurately measure the dosage (more info on that below). This is the one I use:

How To Treat – Okay, so you've got your CP + digital scale and are ready to dose! Well, this brings us to the next challenge to overcome: Bacteria and biofilm. All medications (except copper) that you dose into water are susceptible to biodegradation. With Chloroquine this can be a major problem because the medication needs to be at a therapeutic level at all times in order to be effective. Therefore, I highly recommend following one of these QT protocols when using CP:

CP Protocol #1 (preferred): Dose 15 mg/L (60 mg/gal) into a bare bottom, rockless QT (see pic below) and treat for 10 days. The tank (and all equipment) should have been cleaned/sterilized beforehand and no biological filtration should be used! The point is to limit the bacteria/biofilm found in the aquarium which could degrade CP. Ammonia can be controlled by dosing Prime/Amquel every 24-48 hours, or by doing water changes. (A Seachem ammonia alert badge can be used for active monitoring.) However, when performing a water change it is very important to dose CP back into any replacement water before adding it to the QT. This ensures that the concentration of medication in the QT remains therapeutic at all times. After 10 days, transfer the fish into an observation tank (see Posttreatment below) at least 3 m (10 feet) away from the QT.

CP Protocol #2: If you must treat in an established QT with a working biofilter, then you should redose the medication to compensate for possible biodegradation. Start off by dosing 10 mg/L (40 mg/gal) and then subsequently dose 1 mg/L (4 mg/gal) every day thereafter. Daily redosing is ideal, but if that conflicts with your schedule then redosing 3 mg/L or 12 mg/gal every 3 days (for example) should still be adequate. CP has a wide therapeutic range (20-80 mg/gal), so the objective is to keep it within that concentration at all times. After 10 days, transfer the fish into an observation tank (see Posttreatment below) at least 3 m (10 feet) away from the QT.

Posttreatment – To ensure treatment has been successful, transfer the fish into a nonmedicated observation tank for 2-4 weeks. Never transfer the fish directly into your display tank! The point of the observation tank is to ensure treatment has been successful, and symptoms of parasites do not resurface. One way to accomplish this is by housing black mollies (more info) in your observation tank. A freshwater black molly will have no immunity whatsoever to marine diseases, thus making it probable for visible symptoms to show. And evidence of ectoparasites (e.g. ich, velvet, brook) will show up as white spots on a black molly or translucent if a tankmate has flukes.

Pros – Gentle on most fish. (DO NOT USE with Hippo Tangs, anthias and flasher wrasses.) CP treats most external protozoa, and is probably the closest thing there is to a “wonder drug” in our hobby.

Cons/Side Effects – Expensive, hard to get (requires a prescription), powder is heat & light sensitive - so store in a cool, dark place. CP is quickly removed from the water if carbon is used and even by certain filter pads which are made from polyfiber. The medication is also susceptible to biodegradation, which makes dosing in an established QT somewhat unpredictable.

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