Chapter 10

Don’t worry if pharmacology seems a long time ago. Prescribing and giving drugs is easier than it may seem! Although daunting at first, the more prescribing you do, the easier it becomes. In this section, we will explain how to write up drugs and infusions and walk you through prescribing controlled drugs, and at the end of the chapter, there is a table of 75 commonly used drugs with side effects and dosages.


  • The single most useful pharmacology tip is to always refer to the BNF if in any doubt about any drug. As a junior doctor, you will rarely be expected to prescribe drugs that are not in the BNF. Also, it’s worth reading the BNF to improve your pharmacology knowledge; it contains lots of useful information, and time spent familiarizing yourself with the layout will seldom be wasted. For example, it contains prescribing guidelines for the elderly, the terminally ill and children.
  • Make the most of your ward pharmacist. Pharmacists have a wealth of pharmacology knowledge that they can share with you. Not only are they happy to discuss patient management and find alternatives for problematic drugs (or patients), but they are often willing to find recent articles and other information about specific drugs for you. This can be useful for clarifying unusual side effects and for academic talks. They also can tell you about drug interactions, and can help you prescribe unusual drugs as needed.
  • For easy reference, make yourself a chart of common drugs and doses used on the wards and stick it on the front of your folder. It is particularly useful to do this for antibiotics and infusion dosages, which can be painstaking to look up every time you make up an infusion. As always, check the BNF. We have listed the doses of the 75 most common drugs in a table at the end of this chapter for your reference, but it is best to amend it or make your own, especially as different specialties and consultants may have favourites they like to be prescribed.

Prescribing drugs

Drug charts

Drug charts are straightforward to fill out. Basically, there are four parts to a drug chart:

  1. A place for prescribing regular drugs
  2. A place for ‘PRN’ or ‘as required’ drugs
  3. A place for one-off drugs to be given as a ‘stat’ dose or immediately
  4. Fluids and infusions

For each section of the chart, you need to fill in the date, the generic name of each drug, its dose, how frequently it should be prescribed and your signature and bleep number. Abbreviations for prescribing are shown in Table 10.1.

Table 10.1 Abbreviations for prescribing drugs.

Abbreviation Meaning
AC (ante cibum) Before food
PC (post cibum) After food
BD (bis die) Take twice daily
mane Take in the morning
nocte Take in the evening
OD Take once daily
PRN (pro re nata) Take when required
QDS Take four times a day
STAT Take straight away
TDS Take three times a day
T. 1 tablet/dose
T.T. 2 tablets/dose
T.T.T. 3 tablets/dose
x/7 x days
y/52 y weeks
z/12 z months

Tips for filling in drug charts

  • Write legibly. Other people have to administer drugs that you prescribe. Slips of the pens can have huge consequences. Capital letters are often best.
  • In particular, take care in writing dose amounts and units. Micrograms (abbreviated mcg or μg) can easily be mistaken for milligrams (mg); the BNF advises that ‘micrograms’ and ‘units’ be written in full. (A doctor was sued when a patient was given 125 mg of digoxin by a nurse who misread the scrawled ‘mcg’. She had to open many packets of the drug to give such a dose, so also ended up in the dock for failure of common sense.) Using ‘u’ for ‘units’ is also very susceptible to be misread as an additional zero, which can have disastrous consequences. Putting a dot in the middle of the U is a common but not reliable way of attempting to make this practice safer.
  • Develop a good relationship with the ward pharmacist. They are there to help you! They review all drug charts, albeit often after the drug has been given a number of times, and will usually bleep you if you prescribe anything idiotic – this is something you should encourage! Similarly, experienced nurses, who administer many drugs, will usually let you know if you have made a prescription error.
  • Hospital pharmacists usually use green ink. To avoid confusion, use a different colour when writing on drug charts. Black pen is usually best.
  • If drug administration is complicated, write legible additional instructions on the drug chart. There is no harm in writing extra notes to nurses and doctors on the drug chart. In fact it is legally advisable to do so. For some drug administration, hospitals have drug stickers that can be stuck into the drug chart to avoid confusion, for example, with sliding scales for insulin.

Writing prescriptions

FY1 junior doctors are only permitted to write prescriptions for the hospital pharmacy, so outpatient prescriptions and FP10 forms (green general practitioner [GP] prescriptions) shouldn’t be an issue. However, if you do need to write a prescription on plain paper the essential ingredients are:

  • Date
  • Name of patient
  • Patient’s date of birth
  • Address of patient
  • Generic drug name and amount
  • Dose/day
  • Quantity of tablets to dispense
  • Your signature and printed name
  • Your General Medical Council registration number

Controlled drugs

Prescriptions for take-home controlled drugs have to be written in a specific way; otherwise, the pharmacy will send the prescription back. This wastes a spectacular amount of time. To write a controlled drug prescription

the prescription must be in your handwriting – don’t use sticky labels. Include the following:

  • Date
  • Name of patient and their date of birth
  • Address of patient
  • Generic drug name and amount (e.g. ‘10 mg MORPHINE SULPHATE TABS’)
  • Formulation of drug, for example, tablets or patches
  • Dose/day
  • Total number of tablets in both numbers and letters (e.g. ‘10/ten tablets’)
  • Your signature and printed name

  • For example:
    Mr TSD
    2 Tatelman Street
    Wolfchester WC5
    MST continuous tablets 10 mg
    20/twenty tablets
    10 mg twice daily for 5 days
    (Your signature and printed name)


It is now legally suspect to prescribe drugs for patients ‘verbally’ over the phone to nurses. However, in certain instances it still occurs. Typical verbal requests might be ‘Mr Smith has a headache. Could he have two paracetamol please?’ The nurse writes your prescription in the drug chart, with a small note saying, ‘Dr X will sign this’. Verbals are fine for relatively harmless drugs, such as one-off doses of paracetamol or for doses of necessary drugs when you have been held up and coming to the ward is monumentally inconvenient such as a bag of maintenance IV fluids:

  • Check your local hospital policy. Increasingly, verbals are not allowed by trusts. Some trusts only allow them if the medication is already prescribed and in use but a dose change is necessary. Verbals are NEVER acceptable for controlled drugs.
  • It is important to sign verbal requests on the drug chart as soon as possible. Should any problems arise in the interim, the nurse who took the verbal is liable. Because of this, some nurses refuse to take verbals altogether and insist you come to the ward to sign the drug before it is given. This is a reasonable stance for a nurse to take, and you should think twice before you criticize it.
  • Nurses will rightly usually refuse to accept verbals if they think the patient should be seen by a doctor before taking the drug. Whilst this can be frustrating, remember that nurses’ scruples provide a big safety net for you. Everyone remembers times when they were glad that nurses forced them to question what they were doing. Furthermore, blanket prescribing without thinking why that patient may be in pain or vomiting can be quite dangerous.
  • Some hospitals allow a limited number of drugs (e.g. paracetamol, sublingual nitrate, lactulose, and antacids) to be prescribed by nurses after calling the duty doctor. Whilst you do not need to see the patient, it is prudent to check the reasons for the request. You may be required (depending on local policy) to sign for the drugs later.
  • The bottom line is, if in doubt, quickly review the patient and make a decision on what to prescribe based on your findings. This will save you time overall, and you will be reassured that the patient is stable.

Giving drugs

Nurses usually give oral drugs, suppositories, subcutaneous and intramuscular drugs. In most hospitals nurses also give intravenous drugs. However, administration of certain drugs requires a specially trained nurse or a doctor. These vary between hospitals:

  • Never rush when making up a drug or administering it. Being rushed, particularly when doing something unfamiliar, is when mistakes happen.
  • Glass vials are designed to snap at the neck in the direction of the blue dot on their neck. The dot is the ‘weak spot’ and so the bottle is flexed ‘away’ from the dot to break it. Be careful when opening the vials as you can cut yourself on the glass easily. A protective wad of gauze usually helps.
  • Wear gloves or use your non-dominant hand when opening multiple vials. Your dominant hand’s index finger can get chaffed with minute glass splinters if you snap open many glass vials consecutively. It is common to see new doctors in areas like anaesthetics with a constant plaster around their dominant index finger!
  • Avoid using normal saline as a diluent for drugs in patients with liver failure – the extra salt load can precipitate ascites; 5% dextrose is usually preferable.
  • Avoid dextrose in patients with diabetic coma. Give normal saline instead or prescribe as per DKA local hospital protocols. Refer to the BNF for alternative diluents for different drugs. Glucose-containing fluids are also generally avoided in brain-injured patients.
  • If making up cytotoxic drugs, always wear gloves, apron and goggles (and keep your mouth closed!). Wash your hands afterwards with water. Follow local and national protocols and do not do anything you are uncomfortable with. Chemo nurses nowadays usually give chemotherapy, so you may not have to get involved.
  • The plastic containers with prefilled syringes (e.g. adrenaline) in cardiac arrest trolleys are easily opened by holding the box with both hands and twisting it. The syringe then needs to be assembled by screwing the plunger into the syringe body. Make sure you do this at least once for practice before you attend your first arrest.

Drug infusions

Continuous infusions are easy to make up, but they are a complete pain at 4 a.m. Whilst it was traditional to make up midnight infusions like morphine, dopamine and glyceryl trinitrate (GTN) infusions before going to bed, this is now considered bad practice, and the advance preparation of medicines is frowned upon.

To make up an infusion

  1. Find the vial of drug in the drug cupboard. Check the dosage and the expiry date, and ideally ask a nursing colleague to also double check.
  2. Open the vial and draw up the drug into a suitably large syringe, usually 50 ml.
  3. Draw into the syringe the required amount of diluent fluid. This is usually normal saline, sterile water for injection or 5% dextrose, drawn from unopened (sterile) containers.
  4. Label the syringe with a large adhesive label. Specify the following on the label:

    • Date and time you made infusion up
    • Name of patient and DOB
    • Amount of drug in amount of diluent (e.g. 50 mg GTN in 50 ml normal saline)
    • Rate at which solution should run (e.g. 2 ml/hour)
    • Your signature and bleep

Prescribing drug infusions

  1. Prescribe infusions on the fluid section of the drug chart. In some hospitals, this is a separate sheet at the end of the patient’s bed.
  2. Write the following: ‘a units of b drug in x ml of y diluent to run at z ml/hour’. (e.g., ‘500 mg of aminophylline in 500 ml of normal saline. Run at 35 ml/hour’).
  3. To avoid confusion, convert the amount of drug/hour to the amount of infusion to be given every hour (i.e. ml/hour, not mg/hour). To do this, ask yourself the following questions:

    • How many units of drug should the patient get per hour?

      For example, 35 mg/hour (0.5 mg/kg for a 70 kg male).

    • How many units of drug are there per millilitre of infusion?

      For example, 500 mg/500 ml infusion = 1 mg/ml.

    • Therefore, how many millilitres do I need to give so that the patient gets the right amount of units per hour?

      For example, 35 mg/hour ÷ 1 mg/ml = 35 ml/hour


  4. You can always write additional instructions on the drug chart regarding infusion administration.

    For example, 50 mg GTN in 50 ml saline; run at 1–10 ml/hour titrated against chest pain but maintain a systolic blood pressure >100 mmHg.

  5. It is often easier to calculate by making up the drug to a concentration of 1 mg/ml as in the example in the preceding text.
  6. Be mindful of the volume of drug infusions, as they are in addition to normal intravenous fluid infusions, particularly in the elderly, at risk of fluid overload.

Administering infusions

If the nurses are willing to administer infusions, all you have to do is let them know that you have made up the infusion, and where they can find it. Many nurses will make up the infusions themselves and administer them. The safest stance though is to presume that they won’t until you confirm otherwise with them:

  • If you have to run the infusion yourself, then get a nurse to show you how to set up an infusion pump. It is not difficult. Essentially, insert the syringe into the pump with the drug label facing outwards, set the rate on the machine, plug it in, and turn it on. You also have to remember to connect the patient to the syringe.
  • Infusions can run through central or peripheral lines. Many infusions can run concurrently with other drugs through three-way taps or multiple-tap (‘traffic light’) giving sets. These are simple to set up with initial nurse supervision.
  • Some infusions cannot be mixed with others. The most problematic are those containing chelating ions, such as Ca2+. Unfortunately, these require a second Venflon or need flushing with heparinized saline (Hepsal) or saline before another drug is administered through the same line. If in doubt, ask the nurses for help or check the BNF.
  • Place the syringe driver or infusion bag below the level of the patient’s head to avoid the risk of siphoning.

Intravenous drugs

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Sep 27, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on DRUGS

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