Tools of the trade - Equipment used in dosage measurement
Measuring cup - A measuring cup is used to measure liquid and powder forms of medication. A measuring cup measures medication up to 30 ml or the 2 Tablespoon (T) mark. The metric measurements are in milliliters and measure in increments of 5 milliliters beginning at the 5 ml mark near the bottom of the cup to the 30 ml mark at the top of the cup. Usually on the reverse side of the measuring cup are are apothecary measures from 1 dram to 8 drams and 1/8 of an ounce to1 full ounce. Therefore it is easy to see that 8 drams = 1 ounce = 2 T = 30 ml. It is important to use a different measurement tool if you are measuring doses less than 5 ml or a 1/2 tsp or measures greater than 2 T or 30 ml. Elixirs, emulsions and suspensions require the use of a measuring cup to measure the medication dose. Before a medication can be measured accurately you must read the medication label to determine if the medicine needs to be shaken well or diluted before it is poured.
To measure the dosage correctly using a measuring cup follow these rules.
DO place the medicine cup at eye level on a flat surface and pour your medication into the measuring cup to the desired dose.
DO NOT hold the medicine cup at eye level with your hand and pour the medicine into the cup. This creates an incorrect reading for the drug level in the medicine cup and is unsafe if you over pour medication and get it on your hands. Medication can be absorbed through the skin.
The goal is to use a measuring cup to measure an accurate dose to administer to a patient.
Pill splitter - If a pill is scored, has a depressed line across the pill, it can be split in two. The scored tablet has been manufactured to provide equal dosage on both sides of the score of the tablet. For example: Coumadin comes in scored tablets where the 5 mg tablet can be cut in half to provide 2.5 mg of medication. You never use a pill splitter to divide an unscored tablet in two. To do so provides an inaccurate dosage and an uncontrolled administration because the pill is not manufactured to provide equal amounts of medication on either side of the pill. The whole pill must be used to administer the correct dosage. If you have a medication order that requires an unscored tablet to be split in two you must bring this to the attention of the physician and the pharmacist.
Syringe - A syringe is used for parenteral drug administration. Parenteral, for the purpose of this tutorial, means medication is injected into the skin or muscle tissue. Medications can be administered parenterally as an intradermal injection, a subcutaneous injection, or an intramuscular injection. Each method of injection usually requires a specific needle and syringe size.
Needles used in parenteral injections range from the smallest bore (opening), a 27 gauge, to the largest bore (opening) an 18 gauge. Note the gauge, the smallest needle opening has the larger number and the largest opening has the smaller number.
Syringes range from 30 Units to 100 Units for insulin measurement and from 1 ml to 3 ml for other injectable drug measurements.
Intradermal injection requires a very small needle, usually a 25 gauge, at 1/2 inch in length and a 1 ml syringe. This syringe is measured in increments of 0.1 ml to a total dosage of 1 ml. This type of syringe is usually used for skin testing, such as a PPD or Tuberculin skin test, where 0.1 ml of the testing solution is injected bevel up at a 10 -15 degree angle in the dermal layer of skin creating a small upraised (bubbled) area of skin.
Subcutaneous injections (SQ) requires a small gauge needle such as a 25 gauge at a 3/8 to 5/8 inch and a TB or insulin syringe. The medication is injected at a 45 to 90 degree angle into the subcutaneous layer or the fatty layer of skin. The TB syringe is measured in increments of 0.1 ml to a total dosage of 1 ml. The insulin syringe usually comes prepackaged with the appropriate sized needle attached. Insulin syringes are measured in units, and there are three types, a 100 Unit, 50 Unit, and 30 Unit measurement syringe. The smaller the dosage of insulin the smaller the syringe that should be used. If 2 Units of insulin are ordered then it is appropriate to use a 30 Unit syringe even though a 100 Unit syringe can be used. The use of a 30 Unit measuring syringe provides an accurate measurement of this insulin dose. It is important to always use an insulin syringe to measure insulin dosages.
Intramuscular (IM) injections require a 3 ml syringe and a 25 to 21 gauge needle with a 1 inch to 1 1/2 inch length. Since the medication is being injected into the muscle at a 90 degree angle, a larger and longer length needle is used. The only time a 1 inch length needle would be used is for a very thin and frail adult or a child. The 1 1/2 inch needle length is used for all other adults. If the medication is unusually thick, as with penicillin, a very large bore needle, an 18 gauge, is used. If drug amount to be injected is greater than 2 ml it is divided into two equal doses and injected using two syringes. For example, if 3 ml of gamma globulin is ordered to be given, then 2 syringes of 1.5 ml gamma globulin is used and injected into different intramuscular areas.
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