All prescription orders should be legible, unambiguous, dated (and timed in the case of a chart order), and signed clearly for optimal communication between prescriber, pharmacist, and nurse. Furthermore, a good prescription or chart order should contain sufficient information to permit the pharmacist or nurse to discover possible errors before the drug is dispensed or administered.
Several types of prescribing errors are particularly common. These include errors involving omission of needed information; poor writing perhaps leading to errors of drug dose or timing; and prescription of drugs that are inappropriate for the specific situation.
Errors of omission are common in hospital orders and may include instructions to “resume pre-op meds,” which assumes that a full and accurate record of the “pre-op meds” is available; “continue present IV fluids,” which fails to state exactly what fluids are to be given, in what volume, and over what time period; or “continue eye drops,” which omits mention of which eye is to be treated as well as the drug, concentration, and frequency of administration. Chart orders may also fail to discontinue a prior medication when a new one is begun; may fail to state whether a regular or long-acting form is to be used; may fail to specify a strength or notation for long-acting forms; or may authorize “as needed” (prn) use that fails to state what conditions will justify the need.
Poor prescription writing is traditionally exemplified by illegible handwriting. However, other types of poor writing are common
and often more dangerous. One of the most important is the misplaced or ambiguous decimal point. Thus “.1” is easily misread as “1,” a tenfold overdose, if the decimal point is not unmistakably clear. This danger is easily avoided by always preceding the deci-mal point with a zero. On the other hand, appending an unneces-sary zero after a decimal point increases the risk of a tenfold overdose, because “1.0 mg” is easily misread as “10 mg,” whereas “1 mg” is not. The slash or virgule (“/”) was traditionally used as a substitute for a decimal point. This should be abandoned
because it is too easily misread as the numeral “1.” Similarly, the abbreviation “U” for units should never be used because “10U” is easily misread as “100”; the word “units” should always be written out. Doses in micrograms should always have this unit written out because the abbreviated form (“μg”) is very easily misread as “mg,” a 1000-fold overdose! Orders for drugs specifying only the num-ber of dosage units and not the total dose required should not be filled if more than one size dosage unit exists for that drug. For example, ordering “one ampule of furosemide” is unacceptable because furosemide is available in ampules that contain 20, 40, or 100 mg of the drug. The abbreviation “OD” should be used (if at all) only to mean “the right eye”; it has been used for “every day” and has caused inappropriate administration of drugs into the eye. Similarly, “Q.D.” or “QD” should not be used because it is often read as “QID,” resulting in four daily doses instead of one. Acronyms and abbreviations such as “ASA” (aspirin), “5-ASA” (5-aminosalicylic acid), “6MP” (6-mercaptopurine), etc, should not be used; drug names should be written out. Unclear handwrit-ing can be lethal when drugs with similar names but very different effects are available, eg, acetazolamide and acetohexamide, metho-trexate and metolazone. In this situation, errors are best avoided by noting the indication for the drug in the body of the prescrip-tion, eg, “acetazolamide, for glaucoma.”
Prescribing an inappropriate drug for a particular patient results from failure to recognize contraindications imposed by other dis-eases the patient may have, failure to obtain information about other drugs the patient is taking (including over-the-counter drugs), or failure to recognize possible physicochemical incompat-ibilities between drugs that may react with each other. Contraindications to drugs in the presence of other diseases or pharmacokinetic characteristics are listed in the discussions of the drugs described in this book. The manufacturer’s package insert usually contains similar information.
Physicochemical incompatibilities are of particular concern when parenteral administration is planned. For example, certain insulin preparations should not be mixed. Similarly, the simulta-neous administration of antacids or products high in metal con-tent may compromise the absorption of many drugs in the intestine, eg, tetracyclines. The package insert and the Handbookon Injectable Drugs (see References) are good sources for thisinformation.