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Amikacin Injections

Amikacin is the one antibiotic that is still very potent in the treatment of bacterial disease in koi. I base this statement on the sensitivity tests that came back from laboratories. In most cases the bacteria is sensitive to Amikacin.   Amikacin is part of the amino glycosides like Streptomycin Tobramycin Gentamicin etc. and the problem with the use of Amikacin is the perceived/possible impact on the kidneys of koi. It is therefore mostly used as a last resort for koi keepers in treating diseased koi. The fact remains that given in the correct dosages, it will annihilate sensitive bacteria.


If one compares it to other antibiotics, it has a much narrower margin of safety, so caution should be used when determining the correct dosage which will be described later. When injected in the correct dosages it is very effective against gram negative bacteria. This includes Pseudomonas and Aeromonas Similar to most antibiotic treatments, the Amikacin is eliminated through the kidneys and because we cannot determine the renal function of koi, we must assume that it is in an average state.

On this assumption, it should further be assumed that the fist injection will be a safe injection, and normally the problem will be fixed. If the ulcer/lesion does not improve significantly, then the caution comes into play. Consecutive treatments may reduce the renal function and the Amikacin will not be totally eliminated from the fish, causing the follow up injections to reach toxic concentrations. According to Dr Johnson, there is also a high mortality of fish after the third or fourth injection, and the fish displays severe neurological signs. The fish often dies suddenly during handling or stress. It is with this in mind that Dr Johnson in Koi health and Disease, recommends that injections should be given every other day for a maximum of three dosages. In essence the drug will then be active in the fish for 6 days.

This protocol should be enough for the elimination of the bacteria responsible. It should be remembered that antibiotics cannot "cure" the fish. It merely interrupts the negative impact of the bacteria and gives the immune system a chance to get the upper hand.   As mentioned, the safety margin during the use of Amikacin is small and therefore one needs to elaborate a little bit more on the Amikacin dosages used in koi.   It was also suggested that Amikacin be administered once every three days, giving the antibiotic a further three days of activity within the fish. From the literature it is evident that the retention time of the antibiotic in a fish is very difficult to determine accurately, because the metabolism is influenced by water temperature. Studies have however shown that when Amikacin is injected every day, the drug is not fully eliminated from the body by the time the next dosage is applied. There is therefore a build-up of the drug in the fish and normally the fish experience problems after the third injection.

Recommended Dosage

With such diverse opinions on the use of Amikacin, I can therefore only rely on the practical experience that I had. The dosage that I have used many times is 5mg per kilogram of fish, every second day, for a maximum of 3 injections. The problem start for the hobbyist when one considers the fact that Amikacin is available in different strengths. It is therefore not possible to provide a generic table for its use. Please consider the following:

The little bottle of Amikacin contains the liquid that carries the antibiotic, and you need to know the percentage of Amikacin in the liquid. This is printed on the container. You will see on the syringe you will use, that it holds 1ml. It is also essential that you know the weight of the fish.

The dose for Amikacin is 5 mg of active ingredient per kilo of the fish that must be injected.
The 2 ml containers of Amikacin that I use states on the label that 2 ml contains 100 mg of active Amikacin. It is therefore obvious that the 1 ml syringe will contains 50mg of active antibiotic. Therefore a 1 ml syringe will deliver 50mg of Amikacin when injected.


The 1 ml syringe is marked with 50 evenly spaced small lines. The first five lines are further numbered 10, the second five lines are marked 20 etc. These markings coincide very nicely with the dosages required for Amikacin.   The dose level for Amikacin is 5 mg / kilo. The following are examples of how to inject:

A one kg fish needs 1 x 5mg = Amikacin filled up to no 10 on the syringe (0.1 ml)
A two kg fish needs 2 x 5mg = Amikacin filled up to no 20 on the syringe (0.2 ml)
A three kg fish needs 3 x 5mg = Amikacin filled up to no 30 on the syringe (0.3 ml)
A four kg fish needs 4 x 5mg = Amikacin filled up to no 40 on the syringe (0.4 ml)
A five kg fish needs 5 x 5mg = Amikacin filled up to no 50 on the syringe (0.5 ml)
A six kg fish needs 6 x 5mg = Amikacin filled up to no 60 on the syringe (0.6 ml)
A seven kg fish needs 7 x 5mg = Amikacin filled up to no 70 on the syringe (0.7 ml)
An eight kg fish needs 8 x 5mg = Amikacin filled up to no 80 on the syringe (0.8 ml)
A nine kg fish needs 9 x 5mg = Amikacin filled up to no 90 on the syringe (0.9 ml)
A ten kg fish needs 10 x 5mg = Amikacin filled up to no 100 on the syringe (1.0 ml)  

This easy to understand example can be used in future and if the fish weighs for instance 2.5 kg, the dosage will be 25 on the syringe (0.25 ml)  
For the hobbyist that do not have the facilities to accurately weigh the koi, here is an indication of the dosage when you are forced to use fish measurements. The following dosages were calculated on the 100mg per ml Amikacin.

















It is advised to give three injections, one every second day.

Last Updated on Wednesday, 29 February 2012 12:47