What are the consequences of overdosing medication for a sick fish?
Many ornamental fish keepers advise against medicating fish when they are sick, believing that every medicine has some toxicity. Actually, the editor thinks everyone is simply worried about not being able to control the dosage well or misdiagnosing the cause and giving the wrong medication. As for how to diagnose fish diseases, I talked about that in an article I updated some time ago. Today I will talk about the dosage and the choice of drug properties.
Fish medicine refers to substances (including medicated feed additives) used to prevent, treat and diagnose diseases of ornamental fish or to purposefully regulate the physiological functions of ornamental fish. It mainly includes antimicrobial drugs, antiparasitic drugs, microecological preparations, Chinese herbal medicines, external insecticides, disinfectants, nutrients and metabolism improvers, and environment improvers, etc. It belongs to the category of aquatic veterinary drugs. It has the common characteristics of veterinary drugs (for example, it can act directly on the fish body), and at the same time it has the particularity of the application target in its aquatic ecological environment, the difference in application methods, and the characteristic that drug efficacy is more easily affected by the environment. Therefore, its drugs for preventing and treating diseases and improving the breeding environment have more characteristics of the aquaculture environment.
The basic function of ornamental fish medicine is mainly to kill and inhibit the pathogens that cause disease. A relatively ideal fish medicine should have no obvious toxicity to fish, but should be able to inhibit the growth, development and reproduction of pathogens by interfering with their metabolism, thereby helping to give play to the disease-fighting function of the ornamental fish body and achieve the purpose of eliminating and removing pathogens.
(1) Preventive effect
In aquaculture water bodies (including indoor ornamental fish tanks and aquariums and large outdoor breeding ponds), various pathogens may exist at any time, but fish will only become sick after these pathogens reach a certain disease-causing amount. If these pathogens are prevented, killed or inhibited from reproducing and growing early with lower doses of drugs before they reach the disease-causing amount, ornamental fish will not become sick.
(2) Therapeutic effect
After ornamental fish become sick, timely scientific diagnosis should be made, and standard doses should be used for medication, which can better kill and inhibit the growth and reproduction of pathogens, thereby achieving the purpose of treatment. The therapeutic effect on ornamental fish diseases can be divided into two types:
The first is causal treatment, that is, treatment aimed at eliminating the cause of the disease, also called treating the root cause. For example, external drugs can be used to directly kill Sinergasilus and Lernaea, etc.;
The second is symptomatic treatment, that is, treatment by improving certain symptoms of the disease, also called treating the symptoms. For example, external bactericidal drugs such as bleaching powder can be used to treat enteritis, etc., but it can only kill pathogens in the water and on the surface of the fish body, and relieve certain symptoms. It cannot completely cure the disease. Internal bactericidal drugs must also be used at the same time to completely cure it.
The types of ornamental fish medicines sold on the market act on different aquaculture water bodies and different breeding targets. Their effects are often affected by drugs, fish body, diseased body, pathogens and environmental factors.
The effect of ornamental fish medicines is closely related to their physicochemical properties, because these can affect the absorption and metabolism of the drug. For example, heavy metal salts easily undergo chemical binding reactions with body proteins and cause them to precipitate, thus producing irritating, astringent or corrosive effects; para-aminobenzoic acid is a growth substance for certain bacteria, and sulfonamide drugs, because of their similarity in chemical structure, can undergo competitive inhibition and thus exhibit their structural effect. Of course, different manufacturing processes of drugs can also affect the effect of the drug. For example, differences in crushing fineness, mixing uniformity, and production temperature also lead to certain differences in the effect of the drug.
The dose of a drug refers to the amount of drug that produces a certain response in the fish body when administered, and is usually the amount used to prevent and treat diseases. This is because only after a certain dose of the drug is absorbed by the body can a certain drug concentration be reached and the drug effect appear. If the dose is too small, an effective concentration cannot be obtained in the body, and the drug cannot exert its effective effect. But if the dose is too large and exceeds a certain limit, the effect of the drug may undergo a qualitative change and may produce varying degrees of toxicity to the body. Therefore, to give play to the effective effect of the drug while avoiding its adverse reactions, the dosage range of the drug must be strictly controlled. Usually the dose of a drug can be divided into the minimum effective dose, the maximum dose, the common dose, the minimum toxic dose, the toxic dose, and the lethal dose. The smallest dose that can produce an effect is called the minimum effective dose; the largest dose that the body can tolerate without showing symptoms of poisoning is the common dose, which refers to the range of commonly used effective doses in clinical practice; when the drug has exceeded the maximum dose and the body begins to show poisoning, that is what is meant by "every medicine has some toxicity."