Clinical pharmacology and prescribing: Safe prescribing, prescription writing and medicines law

🩺 Safe prescribing, prescription writing and medicines law. Prescribing is one of the commonest things doctors do -and one of the commonest sources of harm. Around 1 in 10 hospital prescriptions written by junior doctors contains an error. Safe prescribing means taking a good drug history, choosing the right drug and dose for this patient, writing it clearly and legally, and checking it. The Prescribing Safety Assessment (PSA) tests these skills before foundation training.
Your four questions for every prescription: Is this the right drug for this patient (indication, allergies, interactions, kidneys, liver, pregnancy)? Is the dose, route, frequency and duration right -and checked in the BNF? Is it written clearly and legally? Does the patient understand it -and what monitoring is needed?

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Principles of Good Prescribing

• GMC "Good practice in prescribing and managing medicines and devices" -prescribe only when you have adequate knowledge of the patient's health and are satisfied the medicine serves their needs.
• Prescribe within your competence; seek advice (senior, pharmacist, BNF, local guidelines) when unsure.
• Take responsibility for any prescription you sign -including those you continue or change.
• The "rights" of medicines administration -right patient, right drug, right dose, right route, right time, right reason, right documentation, right response.
• Before prescribing, check:
  • Allergies and intolerances (and the type of reaction).
  • Indication -is there a clear reason?
  • Contraindications and cautions -kidney and liver function, pregnancy and breastfeeding, age, weight.
  • Interactions with current medicines.
  • Dose -from the BNF (or BNFC) and local guidance.
  • Monitoring needed (bloods, levels, observations).
• Review regularly -antibiotics at 48–72 hours, IV-to-oral switches, stopping medicines no longer needed.
• Shared decision-making -involve patients, consider preferences, and explain benefits and risks (Montgomery -material risks).

The Drug History and Medicines Reconciliation

• A full drug history includes:
  • Prescribed medicines -name, dose, route, frequency, formulation (e.g. modified-release), when started, indication.
  • Over-the-counter medicines, herbal remedies (St John's wort), supplements, vitamins.
  • Other forms -inhalers, eye drops, creams, patches, injections (depot antipsychotics, biologics, methotrexate injections, insulin), contraception, HRT.
  • Recently stopped or changed medicines, and recent courses (steroids, antibiotics).
  • Adherence -how they actually take them; who manages them; compliance aids.
  • Allergies -drug, reaction, severity, when.
  • Recreational drugs, alcohol, smoking (smoking induces CYP1A2 -clozapine, theophylline).
• Sources -patient and carers, GP record, Summary Care Record, patient's own drugs and packaging, community pharmacy, care home MAR chart, hospital letters, specialist clinics (some drugs aren't on GP records -e.g. hospital-only biologics, clozapine, methadone from drug services, chemotherapy).
• Medicines reconciliation -comparing the medicines the patient was taking with those prescribed on admission, using at least two sources, ideally within 24 hours (NICE NG5) -often done with pharmacy.
• Document decisions -continued, withheld (and why, and when to restart), or stopped.
• Don't forget -time-critical medicines (Parkinson's drugs, insulin, antiepileptics, anticoagulants, immunosuppressants after transplant, steroids) must not be missed.

Making a Prescribing Decision

• A structured approach:
  • Diagnosis -is drug treatment needed at all? Consider non-drug options.
  • Goals -what are you trying to achieve (cure, symptom control, prevention)? What does the patient want?
  • Choose the drug -evidence and guidelines (NICE, local formulary, antimicrobial guidelines), effectiveness, safety in this patient, cost.
  • Choose the dose, route, frequency and duration -BNF; adjust for kidneys, liver, weight, age.
  • Check -allergies, interactions, contraindications.
  • Write the prescription clearly.
  • Inform and counsel the patient.
  • Monitor -effect and adverse effects; plan review and stop date.
• Using the BNF -indications and doses, contraindications, cautions, interactions (Appendix 1 -now integrated), renal and hepatic impairment, pregnancy and breastfeeding, monitoring, patient and carer advice, prescribing and dispensing information (e.g. brand prescribing, controlled drug status).
• Generic prescribing -prescribe by generic (approved) name, except where brand matters (e.g. modified-release nifedipine, diltiazem, theophylline, lithium, ciclosporin, tacrolimus, some antiepileptics, insulins, inhaler devices, biologics and biosimilars).
• Formularies -local formularies restrict choices to cost-effective options.

Communicating with Patients About Medicines

• Explain (in plain language):
  • What the medicine is for and how it helps.
  • How and when to take it (with food, time of day, how long).
  • Common side effects and what to do; serious side effects that need urgent help.
  • Monitoring (blood tests) and review plans.
  • What to do if a dose is missed; interactions (including alcohol and OTC medicines).
• Check understanding -"teach-back" ("Can you tell me how you'll take this?").
• Key counselling examples:
  • Methotrexate -once weekly; folic acid on a different day; report sore throat, mouth ulcers, bruising, breathlessness; regular bloods; avoid trimethoprim.
  • Warfarin -INR monitoring, yellow book, bleeding signs, interactions (antibiotics, alcohol, cranberry), consistent vitamin K intake.
  • Steroids -don't stop suddenly, steroid card, sick day rules, take in the morning.
  • Bisphosphonates -on an empty stomach, upright, with water, 30 minutes before food.
  • Inhalers -technique (spacer), rinse mouth after steroid inhalers.
  • Insulin -hypoglycaemia recognition and treatment, injection site rotation, sick day rules, DVLA.
  • Lithium -levels, signs of toxicity, hydration, interactions (NSAIDs, diuretics, ACE inhibitors).
  • Opioids -constipation (laxatives), drowsiness and driving, safe storage.
  • Valproate -pregnancy prevention programme (Pregnancy Prevention Programme -annual risk acknowledgement).
• Written information -patient leaflets, alert cards (steroid, anticoagulant, lithium, methotrexate).
• Driving -sedating medicines; drug driving law (specified drugs -e.g. morphine, diazepam -legal if prescribed and not impaired).

Inpatient Prescriptions

• Hospital drug charts -increasingly electronic (EPMA); the same principles apply.
• Patient details -full name, date of birth, hospital (or NHS) number, ward, weight (and height where needed), allergies (drug and reaction -"no known drug allergies" must be recorded, not left blank).
• Each prescription -drug name (generic, in capitals if handwritten), dose, route, frequency and times, start date, signature, printed name and contact (bleep or GMC number); indication and review or stop date (especially antibiotics).
• Sections of the chart:
  • Once-only and pre-medication (stat doses).
  • Regular medicines.
  • "As required" (PRN) -must include the indication, minimum interval and maximum dose in 24 hours (e.g. paracetamol 1 g oral, 4–6 hourly, max 4 g in 24 hours, for pain).
  • IV fluids and infusions -fluid, volume, rate (duration), additives (e.g. potassium).
  • Oxygen -target saturations (e.g. 94–98% or 88–92%) and device.
  • Anticoagulant, insulin and antimicrobial sections or charts.
  • VTE risk assessment.
• Changing a prescription -cross out the old one (single line, date, sign) and write a new one; never alter doses on the existing prescription.
• Withholding -record the reason and the plan (e.g. "withhold ramipril -AKI -review daily").

Outpatient and Community Prescriptions

• FP10 (England) -GP and community prescriptions; hospital outpatient (FP10HP) or hospital pharmacy prescriptions; increasingly electronic (Electronic Prescription Service).
• Required details:
  • Patient's full name, address, age and date of birth (required for children under 12).
  • Drug name, form, strength, dose, frequency, quantity (or duration), route.
  • Prescriber's signature, date, and address; prescriber identification.
• Validity -most prescriptions are valid for 6 months; controlled drugs (Schedules 2–4) for 28 days.
• Repeat prescribing -needs regular review (at least annual medication review); repeat dispensing schemes.
• Discharge prescriptions (TTOs) -list all medicines, clearly highlight changes (started, stopped, dose changed -with reasons), durations (e.g. antibiotics -stop date; steroids -reducing regimen), monitoring needed, and who is responsible.
• Prescription charges -England charges per item, with many exemptions (age 60 and over, under 16 or 16–18 in education, pregnancy and 12 months after birth, certain conditions -e.g. diabetes on medication, epilepsy, hypothyroidism, cancer; low income); prepayment certificates; free in Scotland, Wales and Northern Ireland.

Rules for Writing Doses

Rule	Correct	Avoid
Write "units" in full (insulin, heparin)	10 units	10 U, 10 IU ("U" read as 0 → 100)
Write "micrograms" and "nanograms" in full	125 micrograms	125 mcg, 125 µg (confused with mg)
Leading zero before a decimal point	0.5 mg	.5 mg (read as 5 mg)
No trailing zero	5 mg	5.0 mg (read as 50 mg)
Avoid decimals where possible	500 micrograms	0.5 mg (if avoidable)
Use generic names, no abbreviations of drug names	ISOSORBIDE MONONITRATE	ISMN, MST, HCT, AZT
Specify formulation where it matters	Morphine sulfate modified-release	"Morphine" alone
Clear frequency	Once daily, twice daily, at 08:00	"od" vs "qd" confusion; "nocte" is acceptable in many trusts
PRN prescriptions	Indication, minimum interval, max dose in 24 hours	"PRN" alone
Weekly drugs	Methotrexate 15 mg once WEEKLY on MONDAYS	"Methotrexate 15 mg weekly" without a named day

• Accepted abbreviations -mg, g, mL, L, kg; routes (PO/oral, IV, IM, SC, PR, SL, INH, NEB, TOP) -follow local policy; write in full if in doubt.
• Legibility -use block capitals for handwritten drug names; sign and print your name.

Drug Calculations

• Basic formula -volume to give = (dose needed ÷ stock strength) × stock volume.
  • Example -morphine 2.5 mg from a 10 mg/mL ampoule → 2.5 ÷ 10 × 1 = 0.25 mL.
• Units -1 g = 1,000 mg; 1 mg = 1,000 micrograms; 1 microgram = 1,000 nanograms; 1 L = 1,000 mL.
• Percentage solutions -1% = 1 g in 100 mL = 10 mg/mL:
  • Lidocaine 1% = 10 mg/mL; lidocaine 2% = 20 mg/mL.
  • Glucose 5% = 50 g/L; glucose 10% = 100 g/L; glucose 50% = 500 g/L.
  • Sodium chloride 0.9% = 9 g/L (about 154 mmol/L sodium).
• Ratio strengths -1 in 1,000 = 1 g in 1,000 mL = 1 mg/mL (adrenaline 1:1,000 -IM for anaphylaxis); 1 in 10,000 = 0.1 mg/mL (adrenaline 1:10,000 -IV in cardiac arrest).
• Weight-based doses -dose (mg/kg) × weight (kg) -e.g. gentamicin 5 mg/kg in a 70 kg patient = 350 mg; check maximum doses (children -don't exceed the adult dose).
• Infusion rates:
  • mL per hour = volume ÷ hours -1 L over 8 hours = 125 mL/hour.
  • Drip rate (drops per minute) = volume (mL) × drops per mL ÷ time (minutes) -standard giving sets about 20 drops/mL.
  • Dose-based infusions -e.g. a drug at 2 mg/hour from 50 mg in 50 mL (1 mg/mL) → 2 mL/hour.
• Opioid conversions (approximate -check local guidance) -oral morphine to SC morphine: divide by 2; oral morphine to oral oxycodone: divide by about 1.5–2; oral codeine is about one-tenth as potent as oral morphine.
• Always double-check -does the answer make sense? (A tenfold error should look wrong.)

Legal Categories and Who Can Prescribe

• Legal categories of medicines (Human Medicines Regulations 2012):
  • GSL (General Sales List) -sold in shops without a pharmacist (e.g. small packs of paracetamol, ibuprofen).
  • P (Pharmacy) -sold under pharmacist supervision (e.g. larger packs, some antihistamines, emergency contraception, co-codamol 8/500).
  • POM (Prescription-only medicine) -needs a prescription from an appropriate prescriber.
  • Controlled drugs -additional legal controls (Misuse of Drugs Regulations 2001).
• Prescribers:
  • Doctors and dentists (dentists -within their practice).
  • Independent prescribers -trained nurses, pharmacists, physiotherapists, paramedics, podiatrists, optometrists, therapeutic radiographers -within their competence (some limits on controlled drugs).
  • Supplementary prescribers -prescribe within an agreed clinical management plan.
• Patient Group Directions (PGDs) -written instructions allowing named registered professionals (e.g. nurses) to supply and give specified medicines to groups of patients without a prescription (e.g. vaccines, contraception, emergency department analgesia).
• Patient Specific Directions -a written instruction from a prescriber for a named patient (e.g. a vaccination list).
• Emergency supply -pharmacists can supply some POMs in emergencies without a prescription (not most controlled drugs).
• Medicines that can be given by anyone in an emergency -e.g. adrenaline (anaphylaxis), naloxone, glucagon, salbutamol inhaler (schools -with conditions).

Controlled Drugs

Schedule	Examples	Key requirements
1	Cannabis (non-medicinal), LSD, MDMA	No therapeutic use; Home Office licence for research
2	Morphine, diamorphine, oxycodone, fentanyl, methadone, pethidine, alfentanil, cocaine, amphetamines (dexamfetamine, lisdexamfetamine), methylphenidate, ketamine, cannabis-based medicines (prescribed)	Full CD prescription requirements; safe custody (CD cupboard); CD register; destruction witnessed
3	Buprenorphine, tramadol, temazepam, midazolam, phenobarbital, gabapentin, pregabalin	CD prescription requirements; safe custody for some (buprenorphine, temazepam); usually no register
4	Most benzodiazepines (diazepam, lorazepam), Z-drugs (zopiclone, zolpidem); anabolic steroids (part 2)	Prescriptions valid 28 days; no special writing rules
5	Low-strength opioid preparations -co-codamol, low-strength codeine and dihydrocodeine, oral morphine solution 10 mg in 5 mL (Oramorph)	Minimal controls; ordinary prescription rules

• Schedule 2 and 3 prescription requirements (community and discharge prescriptions):
  • Patient's full name and address.
  • Drug name and form (e.g. modified-release tablets, oral solution) and strength (if more than one).
  • Dose (e.g. "one tablet twice daily" -"as directed" is not acceptable).
  • Total quantity (or number of dose units) in both words and figures -e.g. "28 (twenty-eight) tablets".
  • Prescriber's signature, date, address; valid for 28 days; usually up to 30 days' supply (good practice).
• Inpatient charts -words and figures are not required, but the drug must still be prescribed clearly; administration is checked and recorded in the CD register on the ward (Schedule 2).
• Instalment dispensing -methadone and buprenorphine for opioid dependence (specific wording).
• Safety -opioid conversions, high-strength preparations (e.g. confusing morphine 10 mg/5 mL with 20 mg/mL concentrate), fentanyl patches in opioid-naïve patients, and combining opioids with gabapentinoids or benzodiazepines (respiratory depression).

Unlicensed and Off-label Prescribing

• Licensed use -a medicine used according to its marketing authorisation (indication, dose, route, age group) granted by the MHRA.
• Off-label -a licensed medicine used outside its licence (different indication, dose, age, route) -very common, especially in children, palliative care (e.g. subcutaneous drugs in syringe drivers), psychiatry and pregnancy (e.g. amitriptyline for neuropathic pain was off-label; aspirin for pre-eclampsia prevention).
• Unlicensed -a medicine with no UK licence (e.g. imported products, "specials" made for a patient).
• GMC guidance -you may prescribe off-label or unlicensed when:
  • It better serves the patient's needs than a licensed alternative, or no licensed option exists.
  • There is sufficient evidence or experience of safety and effectiveness.
  • You take responsibility for prescribing and overseeing care.
  • You give patients enough information (it is off-label or unlicensed) and record your reasons -unless it is accepted routine practice (e.g. paediatrics), where explanation can be briefer.
• Black triangle (▼) medicines -new or under additional monitoring -report all suspected adverse reactions via Yellow Card.

GMC Guidance -Special Situations

• Prescribing for yourself or people close to you -avoid wherever possible; never for controlled drugs except in exceptional emergencies (and record it).
• Remote prescribing (phone, video, online) -only if you have enough information about the patient's health; extra care with controlled drugs, antibiotics, and medicines needing monitoring; access to records.
• Prescribing at the request of others -you are responsible for what you sign (e.g. continuing a hospital specialist's recommendation, or a nurse's request on the ward) -check it is appropriate.
• Shared care -clear agreements between specialists and GPs (e.g. DMARDs, lithium, antipsychotics, ADHD drugs) about who prescribes and monitors.
• Repeat prescriptions -must be reviewed; safe systems for monitoring.
• Conflicts of interest -prescribe in the patient's interest, not influenced by gifts or incentives.
• Patients who refuse medicines -respect decisions of adults with capacity; for those lacking capacity, follow the MCA (best interests; covert medication only with process -see the Older Person chapter).
• Antimicrobial stewardship -prescribe antibiotics only when needed, per local guidelines (see page 5).

Prescribing Errors

• Common types:
  • Wrong dose -tenfold errors, unit confusion, wrong formulation (e.g. modified-release vs immediate-release), failure to adjust for kidneys or weight.
  • Omission -regular medicines not prescribed on admission (or not restarted).
  • Allergy -prescribing a drug to which the patient is allergic (or a related drug -e.g. co-amoxiclav to a penicillin-allergic patient).
  • Interactions -e.g. clarithromycin with simvastatin; trimethoprim with methotrexate.
  • Duplication -two paracetamol-containing drugs (paracetamol plus co-codamol), two anticoagulants (LMWH plus DOAC).
  • Contraindications -NSAIDs in AKI; metformin with very low eGFR; beta-blockers in severe asthma.
  • Wrong patient, illegible or incomplete prescriptions, unclear PRN instructions.
  • Transcription errors -copying charts, discharge letters.
• Causes -lack of knowledge, time pressure, interruptions, fatigue, unfamiliar patients, poor handover, complex patients, lack of checking, look-alike and sound-alike drugs (e.g. hydralazine/hydroxyzine, carbamazepine/carbimazole, chlorpromazine/chlorpropamide, propranolol/prednisolone).
• Prevention -check every prescription (allergies, doses, interactions), use the BNF and local guidance, ask pharmacists, avoid distractions, electronic prescribing with decision support, structured ward rounds with pharmacy, never prescribe from memory for unfamiliar drugs, double-check calculations and high-risk drugs.

Never Events and High-risk Situations

• Medication-related events historically listed by NHS England as "Never Events" (wholly preventable serious incidents):
  • Wrong route administration of chemotherapy -e.g. vincristine given intrathecally (fatal).
  • Overdose of insulin due to abbreviations (e.g. "U") or using a syringe other than an insulin syringe or pen.
  • Overdose of methotrexate for non-cancer treatment (daily instead of weekly).
  • Mis-selection of high-strength midazolam (5 mg/mL or 2 mg/mL) during conscious sedation -use 1 mg/mL in most areas.
  • Administration of medication by the wrong route -e.g. oral liquids given IV (use oral syringes).
  • Mis-selection of a strong potassium solution (concentrated potassium chloride) instead of an intended other solution -use pre-mixed bags.
• Other high-risk medicines (see page 5) -anticoagulants, opioids, insulin, IV potassium, antiepileptics, digoxin, lithium, aminoglycosides, chemotherapy, sedatives, IV fluids in children and older people.
• Allergies -penicillin allergy is the commonest documented allergy; always check before antibiotics (and check for "hidden" penicillins -co-amoxiclav, piperacillin–tazobactam, flucloxacillin, amoxicillin-containing H. pylori regimens).
• Time-critical medicines -Parkinson's medicines, insulin, antiepileptics, antibiotics in sepsis -omissions cause harm.

Reporting and Learning

• MHRA Yellow Card scheme -report suspected adverse drug reactions (and device problems, defective medicines, counterfeit medicines):
  • Report all suspected reactions to black triangle (▼) medicines and in children.
  • For established medicines, report serious reactions (fatal, life-threatening, disabling, hospitalisation, congenital abnormality, medically significant).
  • Anyone can report -doctors, nurses, pharmacists and patients.
• Incident reporting -local systems (e.g. Datix) and the national Learning from Patient Safety Events (LFPSE) service; the Patient Safety Incident Response Framework (PSIRF) focuses on learning and system improvement.
• Duty of Candour -be open and honest with patients when things go wrong (statutory for organisations; professional duty for individuals) -apologise, explain and support.
• Learning culture -errors usually arise from systems; reporting helps prevent recurrence.

The Prescribing Safety Assessment

• The PSA -a national online assessment of prescribing competence, run by the British Pharmacological Society and Medical Schools Council; final-year UK medical students (and some other doctors) must pass it before starting foundation training.
• Format -about 60 questions over 2 hours, with access to the BNF (online), in eight sections:
  • Prescribing -writing new prescriptions on a simulated chart (the most marks).
  • Prescription review -finding errors and problems.
  • Planning management -choosing the best treatment.
  • Communicating information -what to tell patients.
  • Calculation skills -doses, infusions, concentrations.
  • Adverse drug reactions -recognising and managing them.
  • Drug monitoring -what and when to monitor.
  • Data interpretation -acting on results (e.g. INR, levels, U&E).
• Tips -read the whole case, check allergies, weight and kidney function, use the BNF efficiently (dose, renal, interactions), choose the most appropriate option (not just a correct one), and write complete prescriptions (drug, dose, route, frequency, duration).

Prescribing Rules at a Glance

Topic	Rule
Medicines reconciliation	Two sources, within 24 hours of admission
PRN prescriptions	Indication, minimum interval, maximum 24-hour dose
Units and micrograms	Write in full -never "U", "IU", "mcg" or "µg"
Decimals	Leading zero (0.5 mg); no trailing zero (5 mg)
1% solution	10 mg/mL
1 in 1,000	1 mg/mL (adrenaline IM)
Schedule 2–3 CD prescription	Form, strength, dose, total quantity in words and figures; valid 28 days
Schedule 2 examples	Morphine, diamorphine, oxycodone, fentanyl, methadone, ketamine, methylphenidate
Schedule 3 examples	Buprenorphine, tramadol, temazepam, midazolam, gabapentin, pregabalin
Off-label	Allowed with evidence, responsibility, patient informed, reasons recorded
Yellow Card	All reactions to ▼ drugs and in children; serious reactions for others
Self-prescribing	Avoid; never controlled drugs except exceptional emergencies

Spot the Error

Prescription	Problem
"Insulin 10U before meals"	"U" can be read as 0 -write "units"
"Digoxin 125 µg daily"	Write "micrograms" in full
"Warfarin .5 mg"	Missing leading zero
"Bumetanide 1.0 mg"	Trailing zero -risk of 10 mg
"Paracetamol 1 g PRN"	No indication, interval or maximum dose
Co-codamol 30/500 regularly plus paracetamol 1 g four times daily	Paracetamol duplication -overdose
"Methotrexate 10 mg daily"	Should be once WEEKLY with a named day
Co-amoxiclav for a patient with penicillin anaphylaxis	Contains amoxicillin -contraindicated
Clarithromycin added for a patient on simvastatin 40 mg	Interaction -rhabdomyolysis; suspend statin
Trimethoprim for a patient on methotrexate	Antifolate interaction -marrow toxicity
Enoxaparin and apixaban both prescribed	Duplicate anticoagulation
Ibuprofen for a patient with AKI on ramipril and furosemide	"Triple whammy" -avoid NSAID
CD discharge prescription: "MST 10 mg BD, supply 2 weeks"	Brand abbreviation; quantity not in words and figures; form not specified
Fentanyl 25 microgram/hour patch for acute post-operative pain in an opioid-naïve patient	Inappropriate -slow onset, respiratory depression risk
"Hydroxyzine" given instead of "hydralazine"	Look-alike sound-alike error
Gentamicin 7 mg/kg for a patient with eGFR 20 without level monitoring	Needs kidney dose adjustment and level-guided dosing

Exam-style Scenarios

1. A 68-year-old woman is admitted with pneumonia. Her GP record lists amlodipine, ramipril and atorvastatin. Her daughter brings in her medicines, which also include a fentanyl patch (from the pain clinic), weekly methotrexate injections (from rheumatology) and a co-codamol pack she buys over the counter.
Answer: Incomplete GP record -medicines reconciliation is essential.

• Use two or more sources (patient's own drugs, family, GP record, specialist letters, community pharmacy) and involve pharmacy.
• Prescribe the fentanyl patch (check strength and change day) and record methotrexate (day of week -withhold during acute infection after discussion); avoid co-codamol duplication with any paracetamol prescribed.
• Check for interactions (e.g. avoid clarithromycin with atorvastatin and fentanyl -CYP3A4) and document all decisions.

2. A 45-year-old man needs morphine sulfate modified-release 30 mg twice daily on discharge for 14 days.
Answer: Schedule 2 controlled drug discharge prescription.

• Write: Morphine sulfate modified-release tablets 30 mg, one tablet twice daily (every 12 hours), total quantity 28 (twenty-eight) tablets.
• Include patient name and address, prescriber signature, date; prescribe by brand if local policy requires (modified-release morphine products); valid for 28 days.
• Prescribe a laxative and immediate-release breakthrough analgesia if appropriate; counsel about drowsiness, driving and safe storage.

3. You need to give adrenaline IM for anaphylaxis to a 70 kg adult. The ampoule is labelled "1 in 1,000".
Answer: Adrenaline 500 micrograms IM = 0.5 mL of 1:1,000.

• 1 in 1,000 = 1 mg/mL; 500 micrograms = 0.5 mL.
• Give into the anterolateral thigh; repeat after 5 minutes if no improvement.
• Never give 1:1,000 adrenaline IV in anaphylaxis (only specialists give IV adrenaline, titrated in diluted form).

4. A nurse asks you to prescribe "something for sleep" for a 79-year-old patient on the ward who is restless at night. You haven't met the patient.
Answer: Prescribing at the request of others -you are responsible.

• Review the patient -restlessness at night may be delirium, pain, urinary retention, constipation, hypoxia or withdrawal.
• Avoid hypnotics in older people (falls, delirium); non-drug measures (quiet environment, reorientation, sleep routine).
• If a hypnotic is truly needed, use the lowest dose for a short time and document why.

5. A 30-year-old woman with epilepsy asks you to prescribe sodium valproate, which her neurologist recommended.
Answer: Valproate in a woman of childbearing potential -Pregnancy Prevention Programme.

• Valproate is highly teratogenic (neural tube defects, neurodevelopmental disorders) -should not be started in anyone (male or female) under 55 unless two specialists independently consider there is no other effective or tolerated treatment (MHRA 2024), with the Pregnancy Prevention Programme (highly effective contraception, annual risk acknowledgement form).
• Discuss alternatives (lamotrigine, levetiracetam) with the neurologist.
• Document the counselling; give the patient guide.

Key Points

• You are responsible for every prescription you sign.
• Before prescribing -allergies, indication, contraindications, interactions, kidneys, liver, pregnancy, dose, monitoring.
• Medicines reconciliation -two sources within 24 hours; include OTC, specialist and injected medicines.
• Prescribe generically, except where brand matters.
• Write units and micrograms in full; leading zeros, no trailing zeros.
• PRN prescriptions need an indication, interval and maximum dose.
• Methotrexate is weekly -name the day.
• 1% = 10 mg/mL; 1 in 1,000 = 1 mg/mL.
• Schedule 2 and 3 CD prescriptions -form, strength, dose, total quantity in words and figures; valid 28 days.
• Gabapentin, pregabalin and tramadol are Schedule 3; most benzodiazepines are Schedule 4.
• Off-label prescribing is acceptable with evidence, responsibility, information and documentation.
• Never self-prescribe controlled drugs.
• Commonest errors -wrong dose, omissions, allergies, interactions, duplication.
• Report ADRs via Yellow Card -all for ▼ drugs and children.
• Valproate -Pregnancy Prevention Programme; don't start in women of childbearing potential unless no alternative.

Guidelines and Further Reading

• General Medical Council: Good practice in prescribing and managing medicines and devices
• NICE NG5: Medicines optimisation
• British National Formulary: Guidance on prescribing; Controlled drugs and drug dependence
• Misuse of Drugs Regulations 2001; Home Office controlled drug schedules
• British Pharmacological Society and Medical Schools Council: Prescribing Safety Assessment
• Royal Pharmaceutical Society and Royal College of Nursing: Professional guidance on the administration of medicines
• MHRA: Yellow Card scheme; Valproate Pregnancy Prevention Programme
• NHS England: Never Events policy and framework; Patient Safety Incident Response Framework
• Dornan T et al.: EQUIP study -prevalence and causes of prescribing errors by junior doctors
• BNF -for current doses