What are the essential components to include when writing a prescription for a patient with a known medical condition, such as hypertension (high blood pressure) or diabetes mellitus, and potential allergies or interactions with other medications?

How to Write a Prescription

A complete prescription must include patient identification, prescriber credentials, drug specifications (name, strength, dosage form, quantity, and administration instructions), and legal requirements—all written legibly to prevent medication errors that can harm patients. 1, 2

Essential Components of a Valid Prescription

Patient Information

• Full name, age, sex, and address are mandatory to ensure correct patient identification 1
• Out-patient file number or medical record number should be included for institutional tracking 3
• Contact information (phone number) facilitates follow-up and clarification if needed 3

Prescriber Information

• Full name, qualification, and registration number (e.g., NMC registration) are legal requirements, though commonly omitted in practice 1
• Department name and contact details allow pharmacists to verify unclear orders 3
• Date of prescription and signature are essential—signature omission occurs in approximately 16% of prescriptions 1
• The symbol "Rx" (superscription) should precede the medication list, though it is missing in 67% of prescriptions 1

Drug Information (The Critical Component)

• Generic drug name should be used preferentially over brand names to reduce costs and confusion 4
• Strength must be specified (e.g., "10 mg")—this is omitted in 40% of prescriptions 1
• Dosage form (tablet, capsule, syrup, injection) must be stated—missing in 12% of cases 1
• Dose and frequency (e.g., "10 mg once daily") are essential—omitted in 19% and 10% of prescriptions respectively 1
• Route of administration (oral, IV, topical) should be explicit—missing in 63% of prescriptions 1
• Duration of therapy prevents indefinite continuation of medications 1
• Total quantity to be dispensed must be clearly stated—absent in 60% of prescriptions 1

Special Considerations for Patients with Chronic Conditions

For Hypertension Patients

• ACE inhibitors (e.g., lisinopril 10 mg once daily) or ARBs are first-line for patients with diabetes, chronic kidney disease, or albuminuria 5, 6
• For uncomplicated hypertension, thiazide-like diuretics or calcium channel blockers are equally appropriate first-line options 5
• Beta-blockers should be reserved for patients with prior MI, active angina, or heart failure—they are not preferred for uncomplicated hypertension 5
• For Black patients, calcium channel blockers or thiazide diuretics are more effective than ACE inhibitors or ARBs as initial monotherapy 5
• Combination therapy is often required—logical combinations include (ACE inhibitor or ARB) + (calcium channel blocker or diuretic) 5

For Diabetes Patients

• ACE inhibitors or ARBs are strongly recommended for blood pressure control in diabetic patients 5
• Target blood pressure is <130/80 mmHg for patients with diabetes 5
• Avoid beta-blocker plus diuretic combinations in patients at high risk for developing diabetes (obesity, metabolic syndrome, family history) due to increased diabetes incidence 5
• Statins should be prescribed for cardiovascular risk reduction—target LDL <100 mg/dL (or <70 mg/dL for very high-risk patients) 5

Checking for Drug Allergies and Interactions

• Document all known drug allergies prominently on the prescription 5
• ACE inhibitors are contraindicated in pregnancy, bilateral renal artery stenosis, history of angioedema, and hyperkalemia 5, 6
• Statins interact significantly with protease inhibitors—use pravastatin or pitavastatin, or start atorvastatin/rosuvastatin at low doses with careful titration 5
• NSAIDs, steroids, and oral contraceptives can raise blood pressure—review all over-the-counter and prescribed medications 5
• For patients on warfarin, aspirin, or clopidogrel, avoid prescribing additional antiplatelet agents without clear indication due to bleeding risk 5

Practical Prescribing Algorithm

Step 1: Evaluate and Define the Problem

• Confirm diagnosis (e.g., hypertension with diabetes) 4
• Assess cardiovascular risk factors, target organ damage, and comorbidities 5

Step 2: Specify Therapeutic Objective

• For hypertension with diabetes: target BP <130/80 mmHg 5
• For heart failure: reduce signs/symptoms and mortality 6

Step 3: Select Appropriate Drug

• For hypertension + diabetes: start ACE inhibitor (lisinopril 10 mg once daily) 5, 6
• For hypertension + prior MI: ACE inhibitor or ARB plus beta-blocker 5
• For resistant hypertension: add mineralocorticoid receptor antagonist (spironolactone) after maximizing three-drug therapy 5

Step 4: Write the Prescription with Complete Details

• Example: "Lisinopril 10 mg tablets, take one tablet by mouth once daily, dispense #30 tablets, duration 30 days" 6, 1
• Include relationship to food if relevant (e.g., "with or without food")—physicians prefer this clarity 7

Step 5: Provide Patient Information

• Explain the purpose, expected benefits, and potential side effects 2, 4
• Warn about angioedema risk with ACE inhibitors (facial swelling, difficulty breathing requires immediate discontinuation) 6
• Advise patients to avoid NSAIDs which can reduce antihypertensive efficacy and worsen renal function 5
• Provide both verbal and written information—consumer medicine information leaflets are useful adjuncts 2

Step 6: Monitor and Evaluate Therapy

• Recheck blood pressure within 2-4 weeks after initiating or adjusting therapy 5
• Monitor serum creatinine and potassium within 1-2 weeks after starting ACE inhibitors, especially in patients with renal impairment 5, 6
• Adjust doses or add medications if target BP not achieved after 4 weeks 6

Step 7: Consider Drug Cost

• Generic medications should be prescribed whenever possible to reduce patient cost burden 4
• Long-acting formulations improve adherence and provide more consistent 24-hour blood pressure control 5

Step 8: Use Technology to Reduce Errors

• Electronic prescribing systems improve legibility and reduce transcription errors 4
• Access to drug interaction checkers and electronic references prevents dangerous combinations 4

Critical Pitfalls to Avoid

• Never use non-standard abbreviations (e.g., "qd" can be misread as "qid")—write "once daily" instead 1
• Never prescribe sublingual nifedipine for hypertensive emergencies—it causes unpredictable, excessive BP drops 8
• Never combine ACE inhibitor + ARB + direct renin inhibitor—this increases hyperkalemia, syncope, and acute kidney injury without added benefit 5
• Never lower diastolic BP below 60 mmHg in patients with cerebrovascular disease—this risks cerebral hypoperfusion 8
• Never omit strength, quantity, or duration—these are the most common prescription errors 1
• Avoid prescribing statins without checking for drug interactions in patients on protease inhibitors or other CYP3A4 inhibitors 5