Dog owners are often confused about which antibiotics will work best in their sick animals. Without expert veterinary care, owners often prescribe human medications that can be ineffectual and sometimes harmful to their animals. Particularly with bacterial infections, a veterinarian should be consulted to determine which antibiotics work best against which disease for the optimal health of the animal.
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Function
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Ampicillin is a penicillin-like antibiotic used in dogs with bacterial infections. It works by inhibiting cell wall synthesis. Ampicillin has a wide range of clinical use, including fighting urinary tract infections, pneumonia, and skin infections, but resistance to the drug is common. It is available in capsules and liquid suspension and is also injectable.
Metronidazole, trade name Flagyl, is labeled as an antibacterial, antiparasitic, and antiprotozoal drug in veterinary medicine. It works by inhibiting cell function for bacteria and protozoa in the dog's intestinal tract. Resistance to this drug is relatively rare. Metronidazole is available in pills and as an injectable form.
Diseases/Symptoms
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Metronidazole is mainly used in canines diagnosed with intestinal disease. Whether the disease is bacterial (enteritis) or protozoal (Babesia) in nature will need to be determined by a veterinarian, but the symptoms are similar. Diarrhea is common with the animal often defecating in inappropriate places. The dog may become lethargic, weak and dehydrated due to its unwillingness to eat and drink. Vomiting and fever are also common symptoms of intestinal problems.
Veterinarians recommend ampicillin for a variety of illnesses, most often infections of the body's soft tissues. Skin, lung and urinary tract infections show differing symptoms, ranging from an inability to breathe to problems in urination and should be treated by a veterinarian as soon as the symptoms present themselves.
Dosages
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For a 20-pound dog, the normal dosage for ampicillin can range from 180 mg to 360 mg in pill form three times a day for anywhere from ten days to two weeks depending on the type and severity of the illness. Doses as high as two-and-a-half times that much have been recommended for especially resistant bacteria.
Veterinarians, usually prescribe Metronidazole, or Flagyl, in doses of 135 to 150 mg twice a day for 20-pound animals. Treatment may last anywhere from one week to ten days and is usually discontinued soon after symptoms disappear. Metronidazole is a particularly large pill with a very bitter taste and may need to be wrapped in a palatable substance for the animal to ingest it willingly.
Considerations
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Any dog showing symptoms of an infection should be seen by a veterinarian as soon as possible so that the vet can diagnose and treat the illness with the proper medication in the proper dosage. Antibiotics in particular can cause a disease to become treatment resistant if they are not given over the prescribed amount of time. Both ampicillin and metronidazole must be administered in the right amount or the dog may incur stomach upset. The animal needs to be monitored closely by both its owner and the vet. It is also important for owners to remember that if the infection recurs, the veterinarian may want to recommend further tests to determine if another type of antibiotic will be more effective.
Warning
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Metronidazole is not recommended for use in pregnant dogs as it has been shown to produce birth defects in lab animals. Overdoses have been reported to produce loss of balance, pronounced head tilt, lethargy, depression, vomiting and nystagmus (rapid, repeated horizontal eye movement). These effects have also been observed in animals that have treated with the drug for long periods of time.
Dogs who are allergic to penicillin-like drugs should not be given ampicillin. Signs of an allergic reaction include inflammation of the nose, mouth and airway resulting in labored even obstructed breathing. If the ampicillin is injected, there may be swelling and redness in the area around the injection site. When administered orally, diarrhea may occur with large or long-term dosage.
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