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What to Know About Weights, Measures, and Doses
10/2/2009
By Dave Sparks DVM, Oklahoma State University Extension Food Animal Health Specialist
Grams, kilograms, ml, cc; what does it all mean? What cattleman hasn’t stood with medication in hand and wondered if he was helping or making things worse with a wrong dosage. It really isn’t complicated, but it may seem that way to livestock producers who do not use these applications in everyday life. Let’s open the curtains and see if we can let some light in on the subject.
The basic unit of volume in the metric system is the liter. It is slightly larger than a quart, 1.06 times the volume of a quart to be exact. Liters are commonly divided into milliliters, abbreviated ml. Each milliliter is equal in volume to a cube which is one centimeter wide, one centimeter long, and one centimeter high. Thus one milliliter (ml) and one cubic centimeter (cc) express the same unit of volume and can be used interchangeably. There are 30 cc or ml in 1 fluid ounce. As every housewife knows there are 6 teaspoons or 2 tablespoons in a fluid ounce, so there are 5 cc or ml in a teaspoon, or 15 cc or ml in a tablespoon.
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Volume Conversions
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U.S.
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Metric
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1 cup = 8 fl oz
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1 ml = 1cc
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1 pint = 16 fl oz
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1000 ml = 1 liter
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1 qt = 32 fl oz
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1000 cc = 1 liter
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1 fl oz = 30 cc
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1 qt = 0.95 liters
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1.06 qt = 1 liter
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1 teaspoon = 5 cc
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1 tablespoon = 15 cc
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The basic unit of weight in the metric system is the gram. (See the conversion chart below.)
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Weight Conversions
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1000 grams = 1 kilogram
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1000 milligrams = 1 gram
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2.2 lb = 1 kilogram
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1 lb = .45 kilogram
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1 lb = 454 grams
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1 oz = 31.1 grams
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Appropriate dosages of pharmaceuticals are often expressed in grams or milligrams per unit of body weight of the animal to be dosed. When medications are given, they are commonly measured in units of volume such as cc or fluid ounces.
To determine the correct dose for an individual animal you need to know the concentration, which is the amount of the drug expressed in units of weight that will be present in each unit of volume of the product. For example, an antibiotic is packaged and distributed at a concentration of 200 milligrams per milliliter. The recommended dose is 9 milligrams per pound of body weight.
How many cc would you give a 120 pound calf? 120 pounds time the 9 milligrams required for each pound of body weight equals 1080 milligrams required. Since we know that the concentration of the product is 200 mg/ml. we can divide 200 into the requirement of 1080 and find that we need 5.4 ml, or since they are the same, 5.4 cc. Dosages for oral medications are often expressed in fluid ounces rather than ml or cc. The same principles apply in that we need to know the amount of the drug required and the concentration of the product as supplied.
Most over-the-counter drugs have dosing guidelines that are very easy to interpret. Prescription drugs, however, may express the dosing guidelines in terms that are not so familiar, and drugs for off label usage will have no guidelines for that application, other than what your veterinarian provides. It may be helpful to know that a dosage level of 1 mg/kg of body weight is equal to 46 mg/100lbs of body weight. If dosage is expressed in units of volume you can remember that 1 milliliter or cc / kg of body weight equals .46 milliliter or cc / pound of body weight.
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Dosage Conversions
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1 mg/kg BW = .46 mg/lb BW
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1 mg/kg BW = 46 mg/100 lb BW
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1cc/kg BW = .46 cc/lb BW
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Although today we are blessed with many effective drugs to safeguard the health of our livestock, minor errors in dosage can result in major problems. Always follow the label directions carefully. If you are not clear on what to use, how much to use, or how best to administer the drug, you should always consult your local veterinarian.
In many countries of the world, producers are not allowed to self administer drugs to their livestock, and health conscious groups within this country are concerned about the practice here. Their concern is that the use of pharmaceuticals in livestock, and especially the improper use, jeopardizes their effectiveness in human medicine. The future of our ability to medicate our livestock depends on how good a job we do of using drugs responsibly today.
Click here to read more from Oklahoma State University's Cow-Calf Corner.
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