APPOPRIATE PRESCRIBING MEDICINE

• Evaluate and clearly define the patient's problem• Specify the therapeutic objective.• Select the appropriate drug therapy.• Initiate therapy with appropriate details and consider

nonpharmacologic therapies.• Give information, instructions, and warnings.• Evaluate therapy regularly (e.g., monitor treatment results,

consider discontinuation of the drug) .• Consider drug cost when prescribing.• Use computers and other tools to reduce prescribing errors.

Primum non nocere • Hippocrates' advice still holds today. • Prescribe only where necessary, and consider benefits versus

risks.• Involve the patient in decisions about their care and respect

patient autonomy. • Note the patient's age, medical history (especially of any

hepatic or renal dysfunction) and any concurrent medication.• Think about dosage carefully; manufacturers' recommended

doses are based on population studies and assume 'one dose fits all'. However, there are genetic differences.

• New drugs are often marketed at the highest therapeutic level to demonstrate effectiveness in large numbers of patients but companies are not required to provide data on lowest effective dose.

Safe prescribing

• Evidence-based prescribing • Interaction with other drugs • Concordance, tolerability and formulation • Adverse effects • Checking dosages • Using prescribing formularies

Key recommendations for practice• Scenario 1: A five-year-old boy who had pink eye and a clear ocular

discharge was started on antibiotic drops four days ago and initially improved, but today the redness and irritation has returned.

• Scenario 2: A patient seen yesterday for a sleep-depriving cough was started on antibiotics, but the cough still kept her awake last night.

• Scenario 3: A generally healthy 70-year-old woman who takes nonsteroidal anti-inflammatory drugs (NSAIDs) for her osteoarthritis now reports ankle edema. In your absence, a colleague had started her on a calcium channel blocker for newly diagnosed hypertension.

• Scenario 4: A 20-year-old woman with sinus pain who was prescribed a fluoroquinolone by the overnight call physician called this morning to request a cheaper alternative medication.

• Scenario 5: A 29-year-old woman has presented to the office. She is obese, has type 2 diabetes, and is reporting elevated blood pressures measured at home and at work. You are considering starting her on an angiotensin-converting enzyme inhibitor.

Evaluate and Clearly Define the Patient's Problem

• In scenario 1, the child treated with antibiotic drops likely had a viral conjunctivitis that did not need specific treatment. If the child has become sensitive to the prescribed medication, his recurrent symptoms represent morbidity related to an unnecessary prescription.

• In scenario 4, it is assumed that the woman with sinus pain was diagnosed with a bacterial infection over the telephone on the basis of a symptom, rather than as part of an examination. Prescribing a quinolone to a woman of childbearing age exposes her child to serious teratogenic side effects if she turns out to be pregnant. Defining the problem clearly as “sinus pain in a woman of childbearing age” might have led to a more appropriate management course

Specify the Therapeutic Objective• Specifying the therapeutic objective allows physicians to direct

prescribing to a clear goal with expected outcomes. This can be illustrated using several of the clinical scenarios. In scenario 5, which involves the woman with diabetes and the added diagnosis of hypertension, one clear therapeutic objective would be to obtain sustained blood pressure readings of less than 130/80 mm Hg.

• In scenario 2, which involves the patient with nocturnal cough, the objective of restoring sleep was not met with the antibiotic prescription; the antibiotic was most likely unnecessary. For the woman with sinus pain (scenario 4), even if an antibiotic was necessary, prescribing a medication that the patient could not afford clearly missed the therapeutic objective.

Select the Appropriate Drug Therapy

• The WHO guide suggests that physicians develop a formulary of personal drugs (P-drugs). P-drugs are effective, inexpensive, well-tolerated drugs that physicians regularly prescribe to treat common problems. Detailed guidance on developing a personal formulary can be found in the WHO manual, which is available at http://whqlibdoc.who.int/hq/1994/WHO_DAP_94.11.pdf.2 The STEPS (Safety, Tolerability, Effectiveness, Price, Simplicity) framework also can help with building a P-drug formulary.

Select the Appropriate Drug Therapy

• In scenario 3, which involves the patient with osteoarthritis, inappropriate prescribing may have been harmful. Her hypertension may be a side effect of the NSAID she was receiving, and her ankle edema could be a side effect of the antihypertensive she was receiving. Perhaps the NSAID should have been discontinued and an adequate dose of acetaminophen, taken three or four times daily, should have been prescribed for her pain rather than adding another medication and inducing a second side effect. This example illustrates that it is important to consider a patient's age, chronic disease status, and other medications currently being taken before choosing a treatment.

Initiate Therapy with Appropriate Details and Consider Nonpharmacologic Therapies

• Prescriptions should be clear, legible, and written in plain language. The National Coordinating Council on Medication Error Reporting and Prevention recommends eliminating most abbreviations for medication instructions, such as qd (daily), qid (four times daily), and qod (every other day). They also recommend eliminating abbreviations for drug names, such as MSO4 (morphine sulfate). To be effective, prescribers should eliminate nonstandard abbreviations that are easily misread, such as non-native language characters (e.g., μ). Using plain native language for all prescription writing allows the patient to read and draw attention to any errors.

Initiate Therapy with Appropriate Details and Consider Nonpharmacologic Therapies

• Prescriptions should include specific indications for anticipated duration of therapy. For example, write out “as needed for severe back pain” instead of using the abbreviation prn (as needed). Adding the statement, “instructions in Spanish please,” to the prescription (perhaps implemented as a check box on the prescription form) offers a safety net for physicians and pharmacists to reduce prescribing errors for Spanish-speaking patients. Patients taking complex prescriptions like prednisone tapers may need additional written instructions, as may visually impaired patients who have difficulty reading medicine bottle labels. Physicians should consider reducing transcription errors by prescribing electronically

Consider Nonpharmacologic Therapies

• Nonpharmacologic therapy remains an important treatment option. In scenario 5, the woman with diabetes and the added diagnosis of hypertension may not need medication if she loses weight and exercises. A patient with chronic headaches may respond to relaxation training, and a patient with insomnia may improve with better sleep hygiene. Studies have shown that physicians often write prescriptions of doubtful benefit because of perceived pressure to prescribe medications. However, these perceptions may be inaccurate. Asking a patient directly about therapeutic goals may shed light on his or her willingness to use nonpharmacologic options when available.

Give Information, Instructions, and Warnings

• Physicians should educate patients about the intended use, expected outcomes, and potential side effects for each prescribed medication

• it is important to address the common and the rare but serious ones

• Physicians must describe how the medication should (and should not) be administered, including any important relationships to food, time of day, and other medications being taken by the patient

Give Information, Instructions, and Warnings

• Physicians also may want to highlight special drug-related information such as avoiding alcohol when taking metronidazole (Flagyl), staying out of the sun when taking tetracycline, and the possibility of sexual side effects with selective serotonin reuptake inhibitors. Explaining that certain side effects are time-limited can help prevent a patient from discontinuing a needed therapy. Patients can demonstrate their understanding of the medication by repeating back pertinent information. At the end of the visit, the prescriber should ensure that the patient knows when to return for monitoring and whether therapy continues after this single prescription

Evaluate Therapy Regularly

• Systematically reviewing medications at every visit allows the prescriber to monitor treatment effectiveness and reduce problems, particularly in older patients who are most susceptible to polypharmacy.

• A medication review may include revisiting a diagnosis, evaluating possible side effects, searching for drug interactions, and ceasing unnecessary medications.

• A review also helps avoid the prescribing cascade, which involves a physician adding additional drugs to a patient's regimen to treat side effects of other medications.

Consider Drug Cost When Prescribing

• Physicians often fail to consider cost as an important prescribing factor

• In one study, two thirds of older patients planned to underuse their medications because of cost. Even for patients not requiring chronic medications, filling a prescription that costs the equivalent of several days' pay can be an unpleasant shock.

• Asking about a patient's access to a medical prescription card can help to avoid formulary conflicts and delays in starting therapy.

• A local pharmacist also can suggest alternatives that decrease cost.

Writing prescriptions

• if you are hand-writing one, • write legibly in indelible inkdate the prescription and state the full name and

address of the patient.• All prescriptions should be signed by the prescriber.• It is a legal requirement in the case of prescription-only medicines to state the age

for children under 12 years, but it's good practice to do so in all cases. • Other things to take care of include:• Write generics unless there are bioavailability issues, as this will enable the

pharmacist to dispense any suitable preparation, avoiding expense and delay. • Avoid unnecessary use of decimal points (eg 3 mg, not 3.0 mg). • For quantities less than 1 gram, write in milligrams (eg 500 mg, not 0.5 g).• For quantities less than 1 milligram, write in micrograms (eg 100 micrograms, not

0.1 mg). • Don’t abbreviate micrograms, nanograms or units. Use millilitres (ml or mL) not

cubic centimeters or c.c.

Writing prescriptions

• Schedules should preferably be written in native language, without abbreviation

• For prn dosage, state minimum dose interval and maximum total amount. • Specify the strength and quantity. In the absence of this information the

pharmacist will attempt to contact you. If unable to do so, they can use their discretion and professional judgement to dispense up to five days' worth of treatment or appropriate amounts of combination packs or oral contraceptives. If they have insufficient information to make a judgement, they will return the prescription to you.

• If you want anything other than the name, strength, and dosage of the tablets to appear on the label, write it on the prescription in inverted commas - eg 'Sedative Tablets'.

• Avoid abbreviations of drug names and preparations as these can be misinterpreted.

• Don't invent compound generic names, especially for sustained-release preparations.

Prescribing in children

• Children, and particularly neonates, differ from adults in their response to drugs. Special care is needed in ensuring the drug prescribed is appropriate and that the correct dosage is given, especially in the neonatal period.

Factors affecting drug disposition in children

• Oral absorption: – Variable gastric and intestinal transit time: in young

infants, gastric emptying time is prolonged and only approaches adult values at around 6 months of age. In older infants, intestinal hurry may occur.

– Increased gastric pH: gastric acid output does not reach adult values until the second year of life.

– Other factors: gastrointestinal contents, posture, disease states and therapeutic interventions, such as drug therapy, can also affect the absorption process

Factors affecting drug disposition in children

• Distribution: – Increased total body water: as a percentage of total

body weight, the total body water and extracellular fluid volume decrease with increasing age. Neonates require higher doses of water-soluble drugs, on an mg/kg basis, than adults.

– Decreased plasma protein binding: plasma protein binding in neonates is reduced as a result of low levels of albumin and globulins and an altered binding capacity. High circulating bilirubin levels in neonates may displace drugs from albumin

Factors affecting drug disposition in children

• Metabolism: – Enzyme systems mature at different times and may be

absent at birth, or present in considerably reduced amounts.– Altered metabolic pathways may exist for some drugs.– Metabolic rate increases dramatically in children and is often

greater than in adults. Compared with adults, children may require more frequent dosing or higher doses on an mg/kg basis.

• Excretion: – Complete maturation of renal function is not reached until

6-8 months of age.

Route of administration and drug regimes

• Compliance in children is influenced by the formulation, taste, appearance and ease of administration of a preparation.

• Prescribed regimens should be tailored to the child's daily routine. Where possible, treatment goals should be set in collaboration with the child.

Route of administration and drug regimes

• Whenever possible, the use of products which avoid the need for administration during school hours should be considered (eg modified-release preparations or drugs with long half-lives). When administration at school is unavoidable, consideration should be given to prescribing and supplying the school time dose in a separate labelled container.

• Most schools will request written permission from parents to administer the medicine, or may ask parents to return to school to give the medicine themselves.

• Whenever possible, painful intramuscular (IM) injections should be avoided in children.

Prescription writing• Inclusion of age is a legal requirement in the case of prescription-only

medicines for children under 12 years of age, but it is preferable to state the age for all prescriptions for children. It is particularly important to state the strengths of capsules or tablets.

• Although liquid preparations are particularly suitable for children, they may contain sugar which encourages dental decay. Sugar-free medicines are preferred for long-term treatment. Many children are able to swallow tablets or capsules and may prefer a solid dose form; involving the child and parents in choosing the formulation is helpful.

• When a prescription for a liquid oral preparation is written and the dose ordered is smaller than 5 mL, an oral syringe will be supplied.

• Parents should be advised not to add any medicines to the infant's feed, since the drug may interact with the milk or other liquid in it; moreover the ingested dosage may be reduced if the child does not drink all the contents.

Dosages

• Children are not mini-adults. Pediatric doses should be obtained from a pediatric dosage reference text and not extrapolated from the adult dose.

• When considering drug use in children, the following age groups should be used: neonate (birth to 1 month), infant (1 month to 2 years), child (2 to 12 years) and adolescent (12 to 18 years).

Dose calculation

• Children's doses may be calculated from adult doses by using age, body-weight, or body-surface area, or by a combination of these factors. The most reliable methods are those based on body-surface area.

• Body-weight may be used to calculate doses expressed in mg/kg. Young children may require a higher dose per kg than adults because of their higher metabolic rates.

• Other problems need to be considered. For example, calculation by body-weight in the overweight child may result in much higher doses being administered than necessary; in such cases, dose should be calculated from an ideal weight, related to height and age

Dose calculation

• Body-surface area estimates are more accurate for calculation of pediatric doses than body-weight since many physiological phenomena correlate better to body-surface area.

• Body-surface area may be calculated from height and weight by means of a nomogram or using the Body Surface Area (BSA) calculator

Rx• ℞ is a symbol meaning "prescription". • It is sometimes transliterated as "Rx" or just "Rx". • This symbol originated in medieval manuscripts as an abbreviation of the

Late Latin verb recipe, the imperative form of recipere, "to take" or "take thus’’

• Today, when a medical practitioner writes a prescription beginning with " ", he or she is completing the command.℞

• Folk theories about the origin of the symbol ℞ note its similarity to the Eye of Horus or to the ancient symbol for Zeus or Jupiter, (♃), gods whose protection may have been sought in medical contexts.

• The word "prescription", from "pre-" ("before") and "script" ("writing, written"), refers to the fact that the prescription is an order that must be written down before a compound drug can be prepared. Those within the industry will often call prescriptions simply "scripts".