Chloroquine dosing and other considerations
Chloroquine dosing and other considerations
Hello fellow reefers.
I started my journey to eradicate cryptocaryon from my DT a few months ago, and have had quite a few deaths, including some in QT of newly-acquired fish. This has led me to do some research on the drug as it's used in humans, which I thought I would share.
Some caveats:
-I know and respect that many people have had great results with the 10mg/l dose that is commonly used
-I have read that public aquaria use food as a vehicle for feeding the drug to fish
-I am not advising anyone to change their practice based on my recommendations. I'm just sharing information and asking some questions
From studies in people, using chloroquine for treatment or prophylaxis of malaria:
Toxicity:
-Chloroquine has a low margin of safety; the therapeutic, toxic and lethal doses are very close
-Cardiotoxicity may be seen with serum levels of 1 mg/L (one tenth the dose recommended for cryptocaryon prophylaxis in our hobby)
-Serum levels reported in fatal cases have ranged from 1 to 210 mg/L (average, 60 mg/L)
-Acute overdose:Onset of effects is within 30 minutes. Death within 3 hrs.
-Chronic toxicity can cause loss of appetite, blindness, and heart failure
Implications: knowing the lowest effective dose is very important. Anecdotal evidence from aquarists suggests that 5mg/l may not be enough, so 10mg/l seems to be the lowest effective dose, though I have lost small surgeonfish to what looked like acute toxicity at this dose. (I have found surgeonfish to be the most sensitive to this medication's toxic effects)
Absorption and elimination:
-This material is rapidly and almost completely absorbed from the gastrointestinal tract. Peak plasma concentrations within 1-2 hrs.
-Chloroquine is rapidly widely distributed into body tissues. Concentration in the tissues/organs are 10-700 times greater than those in plasma
-Considerable interindividual variations in serum concentration of chloroquine have been reported.
-Drug elimination is very slow. Terminal half-life is 278hrs-60days (different studies)
Implications: chloroquine is rapidly absorbed from the water fish drink (it is very water-soluble) and, once in the fish's body is likely eradicating the trophont stage quickly and may provide protection from reinfection for a long period of time (weeks to months)
Chemical properties:
-the drug is highly water soluble
Implications: once in the tank water, the fish is drinking it in continuously and probably develops therapeutic levels in its tissues fairly quickly (hours)
-the drug is ~50% protein-bound
Implications: protein skimmer should be turned off until you are ready to begin removing the drug from the water
- The drug is listed in one source as being "œsensitive to light"
Implications: Unclear. There is a study from UK that I cannot get full access to that addresses this "“ if anyone can get the full paper we would all appreciate it. Here it is: Photodegradation studies on chloroquine phosphate by high-performance liquid chromatography Elfatih I.A. Karim
The drug reportedly only kills the trophont (in the fish), but not the tomont (encysted reproductive stage which can survive for up to 60 days stuck to substrate/rocks. I do not know if if the theront (free swimming) or protomont (drops off the fish to encyst and become protected as a tomont) are succeptible to the chloroquine in the water.
Obviously the tomont is the problem as it is protected from the drug and can live a long time (probably longer than the medication is viable in the water).
Based on the above, I have modified my quarantine protocol as follows:
1. Use a clean, dry, bare tank with freshly made saltwater with 10mg/l (40mg/gal) of chloroquine phosphate base already in it to introduce new fish into as the initial QT. (If I continue to have deaths with surgeonfish at this dose I may reduce the dose for that species in the future). I may or may not use a sponge filter in that tank "“ more likely dose with Prime daily to keep ammonia in check. I currently use seeded sponge filters in my QT and some PVC elbows.
2. Keep the fish in the initial tank for three days: rationale is that within that period all of the tromonts in the fish should be dead and all of the tomonts have dropped off the fish.
3. After 3 days move the fish to a new, clean QT "“ this one with seeded sponge filters. I plan to keep the fish there for 1 week before moving it to the DT. Rationale: there should not be any tomonts in the new tank, and even if one or two protomonts drops off the fish inte the new tank it's unlikely to mature enough to release tomites within one week of developing.
Your opinions about this are solicited.
