M. and Ferro, A. (2015). Adverse drug reactions. British Journal of Clinical Pharmacology 80 (4): 613–614.16 Riedl, M.A. and Casillas, A.M. (2003). Adverse drug reactions: types and treatment options. American Family Physician 68: 1781–1790.
17 Robertson, D. (2017). First pass metabolism. Nurse Prescribing 15 (6): 303–305.
18 Shamna, M., Dilip, C., Ajmal, M. et al. (2014). A prospective study on adverse drug reactions of antibiotics in a tertiary care hospital. Saudi Pharmaceutical Journal 22 (4): 303–308.
19 Tamargo, J., Le Heuzey, J.Y., and Mabo, P. (2015). Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide. European Journal of Clinical Pharmacology 71 (5): 549–567.
20 Thomson, A. (2004a). Back to basics: pharmacokinetics. Pharmaceutical Journal 272: 796–771.
21 Thomson, A. (2004b). Variability in drug dosage requirements. Pharmaceutical Journal 272: 806–808.
22 VA Center for Medication Safety and VHA Pharmacy Benefits Management Strategic Healthcare Group and the Medical Advisory Panel (2006). Adverse drug events, adverse drug reactions and medication errors. Frequently asked questions. www.pbm.va.gov/PBM/vacenterformedicationsafety/tools/AdverseDrugReaction.pdf.
23 Weinberg, M.A. (2013). Fundamentals of drug action. In: Oral Pharmacology, 2e (eds. M.A. Weinberg, C. Westphal and J.B. Fine), 18–40. New Jersey: Pearson Education Inc.
24 Wesolowski, C.A., Wesolowski, M.J., Babyn, P.S., and Wanasundara, S.N. (2016). Time varying apparent volume of distribution and drug half‐lives following intravenous bolus injections. PLoS One 11 (7): e0158798. https://doi.org/10.1371/journal.pone.0158798.
2 The Prescription and Drug Names
2.1 Parts of a Prescription
1 Q. What are the different parts of a written prescription?
2 A.Heading:Prescriber's name, address, phone number, license number, Drug Enforcement Administration (DEA) number and NPI (national provider identifier) (the DEA number can also be located at the bottom of the prescription by the prescriber's signature)Patient's information (name, address, age, weight)Date of the order (must be written or it is not legal).Body:Rx symbolMedication prescribed (drug name, strength, and formulation) and quantity to be dispensedInstructions to the pharmacist. For example: Dispense 10 capsules.Closing:Signature (Sig): directions to the patientSignature of prescriberWhether or not substitution is permissibleNumber of refillsLabel (informs the pharmacist how to label the medication).
3 Q. What does “Rx” mean?
4 A. Rx is a symbol referring to “prescription.” Rx stands for the Latin word “recipe” or “take thou” or “take thus” or “to take.” Essentially, it is a command to take a specific compound.
5 Q. What does “Sig” mean?
6 A. Sig is an abbreviation for the Latin signatura, meaning “write,” “make” or “label.” These should always be written in English; however, prescribers sometimes use Latin abbreviations, e.g., “1 cap tid pc,” which the pharmacist translates into English as “take one capsule three times daily after meals.”
7 Q. Does the age of the patient need to be written on the prescription?
8 A. Yes. Generally, it is helpful to write in the age (in years) of the patient. For pediatric prescriptions, it is recommended to write in the age of the child if the patient is less than 12 years of age and the age in years and months if less than 5 years of age. Including the weight of the child is also helpful. For Schedule II drugs, it is mandatory to include the age of the patient on the prescription. The reason for writing the age of the patient is that in some cases dose adjustments may be needed.
9 Q. What is the NPI?
10 A. NPI stands for national provider identifier. It is an identification number given to healthcare providers by the CMS (Centers for Medicare and Medicaid Services). Healthcare providers must apply for an NPI number through an application process on the CMS website. Health practitioners need to have this number in order to receive reimbursement from insurance companies and to prescribe medicines.
11 Q. What does the label box at the bottom of the prescription mean?
12 A. Any information about the medication to be dispensed is provided on the label that is affixed to the drug container.
2.2 Generic Substitution
1 Q. When does a brand name drug become generic?
2 A. A brand name drug can become generic when the patent for that drug expires. Once the brand name drug goes off‐patent, several drug companies can begin to manufacture a generic equivalent drug. In the United States, one company is given 180 days of exclusivity to manufacture a generic version of a drug. After 180 days, other manufacturers of generic medications can then start to make their own generic form of the drug. For example, the patent on Celebrex® expired in 2013. Until 2013, Celebrex was not available in a generic form (www.fda.gov/Drugs/DevelopmentApprovalProcess/ucm079031.htm).
3 Q. At the bottom of the prescription there is a section that says “dispense as written” or “substitution permissible.” What is the difference between a generic drug and a brand name drug?
4 A. A generic drug is manufactured and distributed usually without a patent. However, the generic drug may still have a patent on the entire formulation but not on the active ingredient. A drug that has a trade (brand) name is protected by a patent whereby it can only be manufactured and sold by the company holding the patent. Once the patent expires (between seven and 12 years) on a brand name drug, the generic form becomes available (Welage et al. 2001).
5 Q. What is generic equivalency?
6 A. Generic equivalency was developed to save consumers and insurance companies high costs. Generic drugs are much cheaper because of competition between drug manufacturers once the patent has expired. Also, it costs less to manufacture generic drugs. Many brand name drugs have less expensive generic substitutes that according to the FDA are therapeutically and biochemically equivalent to the brand name drug. The FDA requires the bioequivalence of the generic drug (active ingredient) to be between 80% and 125% of that of the brand name drug. Generics are considered by the FDA to be identical in dose, strength, safety, efficacy, and intended use (Balthasar 1999; Greene et al. 2001; Meridith 2003).
7 Q. Is a generic drug always equivalent to a brand name drug?
8 A. According to the law, drug companies are required to prove bioavailability. Many drugs that are available generically are equally efficacious with the equivalent brand name (Birkett 2003).
9 Q. What is generic substitution and how do I know if a generic drug substitute is available?
10 A. Generic substitution is the process by which a brand name drug is dispensed by a different form of the same active substance (Posner and Griffin 2011). There is a book called the “Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations” that all pharmacies have, and since February 2005, there has
