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This document is inteded to give you an overview of some of the common medications (as well as not-so-common ones), their indications (uses), and contraindications (reasons not to use). This document is based primarily upon first-hand experience, documented reference material, and vendor literature. The author assumes no responsibility for any ill-effects or otherwise undesirable outcomes from the use of the information contained in this document. References to brand name products does not imply endorsement, but is, rather, used as an expedient means to demonstrate a medication type. Finally, this document dose not discuss dosage (save specific instances), due to manufacturers variations of medication strength. Please read your packaging and follow the directions indicated.
Before we begin, I thought a bit of microbiology and terminology would be helpful. Don't worry, this won't hurt a bit! What follows is a bit technical and academic, but please bear with me, as it will be helpful later on. I'll do my best to make it fun... c'mon!
Gram-Positive vs. Gram-Negative
In the late 1800s, a biologist named H.C. Gram discovered a property of bacteria dealing with the way their cell walls absorbed and released solutions (stains). Gram discovered that bacteria fell into two distinct categories when stained sequentially with crystal violet, followed in sequence by a bath in iodine, a wash with a destaining agent and a counter stain. If the cells were bathed following an initial treatment with the crystal violet, one group of cells resisted the removal of the crystal violet when washed with ethanol or acetone (both decolorizing agents), whereas the second group was readily decolorized by a brief rinse with these reagents. To visualize the decolorized cells Gram briefly exposed them to a counter stain, or a stain of a different color from the crystal violet. As a counter stain, Gram used the red dye, safranin. Thus cells which resisted decolorization remained a deep purple or blue, and came to be referred to a "gram+" cells, whereas cells that easily lost the crystal violet dye were red after counter staining, and came to be called "gram-" cells.
Gram drew several important conclusions from these staining results. First, he realized that concept of differential staining of cells and cell components was entirely possible. Secondly, he recognized that this staining was a powerful diagnostic tool and could be used to identify cells and organisms. Thirdly, he reasoned that cells and cell components differed chemically as evidenced by their differential staining. Ultimately these realizations led other bacteriologists such as Paul Ehrlich and Robert Koch to the notion of a "Magic Bullet," or a medicine capable of targeting only certain cells and not effecting others. The ability of certain substances to kill microorganisms but not harm the host is the hallmark of modern antimicrobial chemotherapy. This eventually led to the invention of penicillin, by Sir Alexander Fleming in 1929, which heralded the magnificent new world of antibiotics and other chemotherapeutic agents to treat diseases.
Gram+ Cell Wall Characteristics:
The lipid bi-layer cell wall of most gram+ bacteria is covered by a porous peptidoglycan (a polysaccharide/peptide chain... basically a mucus) layer which does not exclude most antimicrobial agents. The crosslinked peptidoglycan molecules form a network which covers the cell like a grid. Approximately 90% of the gram+ cell wall is comprised of peptidoglycan, the remainder is comprised of amino acid bridges.
Gram- Cell Wall Characteristics:
The cell wall of gram- bacteria is much thinner, being comprised of only 20% peptidoglycan, however, gram- bacteria are surrounded by two membranes. The outer membrane functions as an efficient permeability barrier because it contains lipopolysaccharides (LPS) and porins. The inner layer, or periplasmic space, separates the outer plasma membrane from the peptidoglycan layer. It contains proteins which destroy potentially dangerous foreign matter present in this space. The lipid portion of the LPS contains a toxic substance, called Lipid A, which is responsible for most of the pathogenic affects associated with harmful gram- bacteria. Polysaccharides which extend out from the bilayer also contibute to the toxicity of the LPS.
Keep in mind that the cell wall is not a regulatory structure like the cell membrane. Although both are porous, the cell wall is not selectively permeable like the cell membrane, and will, thus, let anything pass that can fit through its gaps. This is where our antibiotics come in!
Ok, enough with the microbiology lesson, let's move on!
Definitions
Special thanks to Leslie Leddo for assisting with the following definitions:
- Antimicrobial:
A general term that refers to a group of drugs that treat microbial infections, including antibiotics, antifungals, antiprotozoals, and antivirals.
- Antibacterial:
A general term that refers to a substance that destroys, specifically, bacteria or suppresses their growth or reproduction.
- Antifungal:
A general term that refers to a substance that destroys, specifically, fungi or surpresses their growth or reproduction.
- Antibiotic:
A chemical substance produced by a microorganism which has the capacity, in dilute solutions, to inhibit the growth of or to kill other microorganisms. Antibiotics that are sufficiently nontoxic to the host are used as chemotherapeutic agents in the treatment of infectious diseases of man, animals and plants.
Antibiotics are generally medicines taken internally. There are, however, antibiotic ointments for topical use, such as Neosporin.
- Bacteriostatic:
An agent that inhibits the growth or multiplication of bacteria. Bacteriostatics do not necessarily kill the bacteria, whereas antibiotics inhibit growth and kill. Many antibiotics that are well resisted have only bacteriostatic effects on the bacteria they are designed to treat.
- Antiseptic:
A topical bacteriostatic.
Examples: Mercurochrome, iodine, betadine.
- Ecto-parasite:
An external parasite. External parasites are those who confine their activities to the outside of the fish, or burrow its way into the skin. These parasites are much easier to overcome than the internal ones by the use of chemical immersions or other treatments.
Examples: Flukes, monogenetic trematodes, isopods, ich, amyloodinium (oodinium), hexamita.
- Endo-parasite:
An internal parasite. Internal parasites are those that dwell inside of the body of the fish, usually in organs and organ tissue. Effective treatments are often harsh, and almost always require ingestion of the medication, making them difficult to eliminate.
Examples: Digenetic trematodes, nematodes (round worms), cestodes (tape worms).
Antibacterials (including antibiotics)
Antibiotics are either gram+, gram-, or both, which is commonly denoted as "wide spectrum". All are indiscriminant killers (within their "gram" designation), which means that they destroy good and bad bacteria alike. The bio-filter, as you may recall, is made up, primarily, of two bacterial strains, Nitrosomonas sp. and Nitrobacter sp., both of which happen to be gram negative (gram-). Both nitrifying bacterial strains are mostly rod-shaped, microbes ranging between 0.6 - 4.0 microns in length. They are obligate aerobes and cannot multiply or convert ammonia or nitrites in the absence of oxygen. This tells us two things:
- Gram- antibiotics will kill the nitrifying bacteria! Ever wonder why SOME antibiotics say they won't harm the bio-filter and other are "bio-filter-safe"? Well, this is why!
- As O2 levels fall, the bio-filter begins to fail as the aerobic nitrifying bacteria die off. With many antibiotics, available O2 levels are diminished by the chemical processes occurring between the bacteria and the antibiotic. This can also result in the decimation of the bio-filter.
In the marine aquarium, the particular bacteria responsible for a bacterial infection is very difficult to ascertain, so we must resort to very wide-spectrum antibiotics, often times to the detriment of the biological filter in the system. Most antibiotics are also lethal to invertebrates, so, if you need to treat with antibiotics, it is best to do it in a hospital tank.
Gram- Antibiotics Commonly Found in the Hobby:
Note: All of these antibiotics will destroy the bio-filter.
- Furazolidone -
- Naladixic Acid - This was once an effective medication, however, as with Penicillin, many bacterial strains have developed resistance to it.
- Neomycin - This is the super-drug for marine creatures. It can be combined with other meds for increased efficacy, but usually will work on its own. If you can only get one medicine, this is the one.
- Oxolinic Acid - Commonly used to treat Koi, this med, although a bit harsh, is still very effective.
- Spectinomycin - Primarily used versus gram- bacterial infections, however, this antibiotic does have effect on some gram+ microbes as well.
- Streptomycin - Generally used to treat Mycobacterium marinum. Can leave water smelling distinctly onion-like. Streptomycin is commonly used in conjunction with Penicillin to create a wide spectrum medication.
Gram+ Antibiotics Commonly Found in the Hobby:
- Erythromycin - Primarily a powerful gram+ antibiotic, this medication also has some effect on gram- bacteria as well as certain fungi.
- Isoniazide - Generally used to treat Mycobacterium marinum (Fish tuberculosis), however, results are not convincing, and it is a very strong medication. Use only as a last resort.
- Penicillin - Not very useful anymore due to high resistance in bacteria.
- Rifampin - Generally used to treat Mycobacterium marinum (Fish tuberculosis). Results are among the best of all meds vs. this disease.
Gram+/Gram- Antibiotics Commonly Found in the Hobby:
- Kanamycin - This is a broad-spectrum, gram+/gram- antibiotic. I will sometimes use this with Neomycin if I am sure there is no fungal infection present. Kanacyn is supposed to treat fungus, but Furanace, in my opinion,e is probably a better choice.
- Methelyne Blue - Methelyne Blue ("meth blue" or "blue") helps relieve the toxic effects of toxic ammonia and nitrite poisoning. This is a good thing to add to your hospital tank when treating, especially if you are not doing water changes. PLEASE READ YOUR MED LABELS FOR POSSIBLE PROBLEMS WITH USING METHYLENE BLUE AND ANTIBIOTICS.
- Metronidazole (Hexamit/Flagyl®) - Works only against anaerobic gram+ and gram- bacteria, and therefore bio-filter safe, but also, of little value versus bacterial infections in the marine tank.
- Nitrofurazone - Excellent wide-spectrum antibiotic found in many combo medications, but rarely on its own.
- Sulfacetamide - Relatively effective wide spectrum antibiotic that uses sulfur as a keratolytic (causing the sloughing of skin) agent. This is intended to assist in the physical removal of the pathogen from the fish's body. Sulfacetamide is most commonly found in the combo drug Triple Sulfa.
- Sulfamethazine - Relatively effective wide spectrum antibiotic that uses sulfur as a keratolytic (causing the sloughing of skin) agent. This is intended to assist in the physical removal of the pathogen from the fish's body. Sulfamethazine is most commonly found in the combo drug Triple Sulfa.
- Sulfathiazole - Relatively effective wide spectrum antibiotic that uses sulfur as a keratolytic (causing the sloughing of skin) agent. This is intended to assist in the physical removal of the pathogen from the fish's body. Sulfathiazole is most commonly found in the combo drug Triple Sulfa.
- Tetracycline - Tetracycline is becoming another antibiotic that is well resisted by many bacteria species, however it still has applications in the aquarium. It is also a fairly good antiprotozoa agent.
Other Antibacterial Agents:
- Iodine - This is a relatively weak antibacterial, due to the fact that contact time must be long in order for the action to be effective. In the absence of other, more effective meds, this can be used, but should be applied many times a day for several days in order to have the desired effect.
- Betadine - A more powerful topical antibacterial agent than straight iodine. Contact time is less, but still relatively long for proper efficacy.
- Melafix® (Maleluca or tea-tree oil) - Maleluca is a somewhat new-age medication, however, results have been very promising. It is a potent antibacterial agent, and also seems to have some restorative properties with respect to tissue regeneration. The oil is added directly to the water, and the fish allowed to bathe in it. There is no evidence to support claims that this compound interferes with respiration in fish, although, you may notice a brief period of panting when first administering, assumedly due to the strong taste/smell. Also, keep an eye on the skimmer, if used, as Melafix will cause excessive wet foam production.
- Mercury Chromium (Mercurochrome/Methiolate) - This is a very difficult-to-find medication because it contains mercury, which has been found to be highly toxic. I would not recommend using it, especially with many other easily found topical antibacterial/bacteriostatic agents available.
- Potassium iodide/Potassium bromide - Commonly found in many coral disinfecting solutions such as Kent Marine's Tech-D. These are relatively powerful oxidizing agents, and can cause chemical burns, so they MUST be diluted. A mix of this and aloe-based conditioners, such as Stress Coat, can make a pasty salve that can be applied that will minmize the chance of tissue damage. The ratio should be 1 part Potassium iodide/bromide to 10 parts Stress Coat. This med is not meant as a tank treatment, and will kill desirable organisms if used as such. Therefore, it should be used only as a dip or a topical solution.
Antifungals
Fungal infections can be either internal, which are relatively common and generally caused by Ichthyosporidium hoferi, or external, which is more rare and generally caused by Saprolegnia sp.. Fungal infections tend to be quite difficult to cure, unfortunately, and internal infections can lead to debilitating secondary illnesses like exophthalmos (pop-eye), and organ damage.
- Formalin - This is a formaldehyde based anti-fungal liquid. Used in conjunction with one of the iodine/betadine/Tech-D® liquids, it makes the topical solution you may have seen us talking about. The solution is effective so far against Snout-Rot (fungal infection) and flesh eating bacteria (bacterial infection).
- Nifurpirinol (Furanace®) - Excellent antifungal and used in conjunction with Neomycin, there ain't a bug on the planet that can survive!! Well, not really, but the combo does make an intense medicine versus both fungal and bacterial infections.
- Phenoxyethanol - Soaking food in a 1% solution of this med can have powerful effects versus internal fungal infections such as Ichthyosporidium hoferi.
- Sodium Chloride (table salt) - High dosages (2-3 teaspoons per gallon) can eliminate some fungi.
Antiparasitics
Parasites come in many flavors... vanilla, chocolate... no wait, that's ice cream. Sorry... Parasites can range from micro to macro, from single-celled to complex organisms, internal and external. Micro-parasites are organisms like Cryptocarion irritans (marine ich) and Amyloodinium ocellatum (marine velvet or coral fish disease), which are common in some marine fish, but rare in seahorses. These organisms are relatively easy to deal with, and most are external. However, there are internal micro-parasites, as well as a handful that are tough to kill. Macro-parasites are organisms such as trematodes, nemotodes, cestodes, and certain crustaceans like isopods. Many of these are internal, and most are relatively difficult to kill without resorting to very powerful medications.
- Acriflavin® - A powerful stain, or "tanning" agent, that cross-links proteins as a part of the bonding/staining action, effectively killing microbes. Although is does effect bacteria, it is primarily used as an antiparasitic agent. Acriflavin is safe and easy to use, will not harm your bio-filter, and is very well tolerated by fish.
- Freshwater Dip - This should be your first-line defense against most parasites. It can also be used prophylactically on new additions to your tank. Most lower parasites and unicellular organisms such as Cryptocarion irritans and Amyloodinium ocellatum do not possess the osmoregulatory system required to survive exposure to freshwater. The salt content within their cell wall causes an osmotic pressure imbalance when the organism is placed in freshwater. This causes the cell to flood with freshwater, essentially lysing (bursting) the cell, and destroying the organism. Fish, on the other hand, can withstand this because they do possess the mechanism to maintain osmotic balance, however, it is taxing on their system, and they can go into osmotic shock during the treatment. If this happens (it will manifest as the fish literally lying down on the bottom of the treatment container), gently tap the fish until it gets up and begins swimming around.
Treatments should be of 5 to 10 minutes in duration, and the water used for the treatment, at the very least, should be of the same temperature as the water the fish is coming out of. Many people recommend adjusting the pH of the freshwater by using baking soda, however, I have found that the fish tolerate this factor quite well, and the pH imbalance seems to enhance efficacy of the treatment.
- GreenEx® - A powerful combination of malachite green and quinine hydrochloride. Malachite green, like Acriflavin or Methylene Blue, is a stain, which permeates the cell membrane and damages the microbe. GreenEx is very effective against most typical marine parasites such as ich and oodinium. GreenEx is safe and easy to use, will not harm your bio-filter, and is relatively well tolerated by fish and inverts.
- Kent Marine RxP® - A pepper-based solution designed to stimulate mucus production, which has the effect of sloughing of parasites while making it very difficult for others in the water column to adhere to the skin of the fish. Most marine parasites must find a host within 24 to 48 hours or they expend their energy reserves and perish, so products like this do not directly kill the parasite, but rather make the possibility of finding a host much more difficult so that they self-annihilate. READ INSTRUCTIONS CAREFULLY, as this med can adversely effect several inverts and certain species of fish.
- Levamisole - This is an excellent medication for treating internal parasites such as nematodes, however, it is only effective if ingested by the fish. This medication may be difficult to get in some areas.
- Malachite Green - The key ingredient in GreenEx®, malachite green is an excellent med for micro-parasites such as Cryptocarion irritans and Amyloodinium ocellatum. It is bio-filter safe and a good choice for treating the whole tank.
- Metronidazole (Flagyl®) - A fair medication for combatting external parasites such as monogenetic trematodes, and Hexamita/Spironucleus. If ingested, this med can also be effective against internal parasites such as digenetic trematodes, nematodes, and cestodes. This is a low impact medication that will not harm the bio-filter, however, there are much more effective medications available such as Levamisole, Niclosamide, and Praziquantel.
- Niclosamide (Mansonil®) - A difficult-to-obtain, but highly-effective medication for treating internal parasites. This medication must be ingested by the fish to function properly. You may need to consult with your veterinarian to obtain this medication.
- Praziquantel (Droncit®) - Another difficult-to-obtain, but highly-effective medication for treating internal parasites. This medication must be ingested by the fish to function properly. You may need to consult with your veterinarian to obtain this medication.
- Quinine Hydrochloride - The secondary medicine in GreenEx®, quinine hydrochloride is the mop up drug that kill off parasites weakened by the staining effects of the malachite green. The addition of quinine hydrochloride greatly enhances the efficacy of malachite green. Quinine HCl is well tolerated by nitrifying bacteria, however, in higher doses (if you use it solely) invertebrates may be harmed.
- Revive® - An excellent medication consisting of Acriflavin, Formalin, and a pH-based potentiator that dramatically enhances the efficacy of both medications. Good stuff to have on hand for emergencies. Rally® is a very similar product with similar ingredients.
- Sodium Chloride (table salt) - High dosages (2-3 teaspoons per gallon) can be a highly effective antiparasitic. For use versus parasites, use as a dip, 5 - 10 minutes in duration. Observe your fish carefully during this time for signs of distress and remove it from the dip if necessary.
- Stop Parasites!® - Another pepper-based agent that can be very effective against Cryptocarion irritans (marine ich) and Amyloodinium ocellatum (marine velvet or coral fish disease). Water must be adequately buffered as this medication with effect the pH dramatically, and can cause acidity to a point where fish loss is possible.
- Trichlorfon (Masoten®, Neguvon®, Dylox®) - These are VERY harsh, but effective medication versus external parasites such as digenetic trematodes, flukes, isopods, etc. This medication is very toxic to inverts, and will damage the bio-filter. Certain fish species such as catfish and sharks can be killed by these meds, and ALL fish should be monitored carefully during treatment.
Combination Drugs
These are medications designed to enhance efficacy, provide wider coverage versus pathogens, and/or medicate while shoring up the fish's immune system. You can make your own combo drugs by mixing certain medications, such as Erythromycin and Penicillin, however, BE VERY CAREFUL WHEN DOING THIS, and know exactly what you are doing. Read all materials on both meds for possible interactions, and if you are unsure, ask. If you are still unsure, or do not get adequate information, DO NOT MIX THE MEDS.
- Furan2® - An excellent combination of nitrofurazone, furazolidone, and methylene blue, this med is highly effective against gram+ and gram- bacteria
- Maracyn I -
- Maracyn II -
- Paragon I -
- Paragon II -
- Spectrogram -
- Triple Sulfa -
A Final Note of Importance
NEVER USE COPPER WITH ANTI-BIOTICS!!! This is VERY important, and I cannot possibly stress this enough. I would also recommend against using malachite green with them as well. Most antibiotics will become quite toxic in the presence of copper sulfate. As you will notice I didn't recommend copper in the list. Although many of you have probably used copper to great effect in the past, it should be noted that it is REALLY hard on the fish, and, although copper is very effective, there are other ways of treating the maladies that copper-based medications cure.
References:
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