Prescribing scenarios and the power of medications

by TheEditor

Categories: Diagnosis, Medicine

In this post I will spend some time understanding the power of medications, then extract some fundamental principles from the GMC’s guidance on prescribing (April 2021). I then analyse two real-world scenarios in prescribing that I have experienced and reference each against the GMC’s guidance.

[The scenarios do not contain information that identifies any patient. Both scenarios are common in medical practice]

A patient requests a medication to treat side-effects of another medication (clozapine) that he is established on. This is done via a nurse who sends me an email. The patient wants Kwells (hyoscine hydrobromide) to treat drooling at night which is a side-effect of clozapine. The patient has been on clozapine for many months. I have never seen the patient before, though he is on my case load as often happens. The patient is unknown to me.

  1. The patient is unknown to me. Therefore, I need to see the patient FTF.
  2. Clozapine is a pretty strong medication licenced for treating treatment resistant or treatment intolerant schizophrenia (those are well defined and will not be explained here).
  3. On occasions – outside of product licence – clozapine is sometimes used to treat mood disorders, or emotionally unstable personality disorder.
  4. I am not told what the patient’s diagnosis is. It is not for me to assume the diagnosis from the treatment. That would constitute slip-shod practice and poor reasoning.
  5. I am unaware of the patient’s physical health.
  6. I am unaware of any other medication the patient is on.

GMC Prescribing Guidance (full): https://bit.ly/GMCRxFullGuidance.

I consider the eight fundamental principles as part of a net of responsibilities, and each of the following:

  • Paragraph 35 : ‘You must have or take an adequate history….‘ requires that doctors should consider the patient’s history which would include: current and recent medicine use and other medical conditions. The GMC does not ‘prescribe’ how doctors should find the history – nonetheless it is obvious that the patient’s account and any relevant medical records should be considered. It will be no defence to say, “The GMC did not say that I should study the medical records“.
  • Paragraph 36 is interestingly prescriptive: “You should encourage your patient to be open about their use of alternative remedies, illegal substances and medicines obtained online or face to face, as well as whether or not they have taken prescribed medicines as directed in the past.
  • Paragraphs 39-40: Focus on the patient’s needs and a range of explanations to be provided. It is about working with the patient. How will a doctor evidence that the latter has been done? It is about documentation of the dialogue with the patient. Shortcuts such as “I’ve done para 39-40” won’t work. Why? Because accountability means that the work has to be truly seen to be done in the documentation.
  • Paras 41-44: deals with the all important matters of capacity.  Again lots of documentation and time spent documenting.
  • Paragraph 45-49: are about giving more information – not just to the patient but any carers involved (para 48). This is particularly important if managing patients who are cognitively impaired, those being treated under legal best interests (S4 of MCA 2005).
  • Para 46: is specific about consulting team members and pharmacists where important to do so.
  • Paragraph 50: specifically gives guidance on consent – which is one step further from capacity.
  • Paragraphs 53-58: cover the importance of sharing information with a range of involved persons.
  • Paragraph 56: creates a firm duty of care to share specific information with the patient’s GP. It is very specific about prescribers who are not the patient’s GP.
  • Paragraph 76 – “If you prescribe based on the recommendation of another doctor, nurse or other healthcare professional, you must be satisfied that the prescription is needed, appropriate for the patient and within the limits of your competence.” In the captioned scenario para 76 applies because the nurse is either recommending or suggesting that the patient be prescribed the medication.
  • Paragraphs 103-109: it is useful to consider that when prescribing anti-side-effect medicine – check whether they fall into unlicensed prescribing. Always check the product license.

After seeing the patient, I need to apply all of the above paragraphs to the letter and make good documentation.

  1. I need to verify the primary diagnosis:
    • From the records, and
    • From my own clinical assessment.
  2. I disregard any cultural or traditional ideas that Kwells is commonly prescribed for excessive salivation (drooling).
  3. I disregard that doing all the above is time intensive. If I am unable to find the time to discharge my responsibilities properly, I will need to inform my medical line managers – stop and not put the patient in foreseeable risk of harm by rushing and cutting corners.
  4. I will need to assess all side-effects from clozapine and focus on hypersalivation.
    1. I will need to determine if the hypersalivation is due to the clozapine or some other confounding condition.
    2. If I determine that the hypersalivation is due to clozapine, then I need to assess:
      1. the degree of the salivation,
      2. its frequency,
      3. any patterns,
      4. impact on quality of life.
  5. Consider with the patient (carers/relatives) possible alternative strategies e.g.
    1. reduction of dose of clozapine if safe to do so.
    2. if the patient is a smoker of tobacco, whether smoking  reduction may help (higher doses of clozapine are needed in smokers because induced liver enzymes metabolise it faster, but some of the side-effects are not well connected to the ‘chemical’ itself).
    3. consider non-chemical solutions e.g. whether this is manageable by using a special pillow and absorbent towel if it is mostly happening at night (as reported).
  6. If after all considerations and exploration of alternatives, Kwells is indicated, then I need to support the patient (carers/relatives) to understand a whole lot of information about what to expect by starting Kwells:
    1. Yes – the drooling may be lessened but it may not. There is no guarantee of efficacy.
    2. I need to educate the patient (and carers or relatives) about the side-effects, adverse effects and rare serious adverse effects. Importantly Kwells has some common bad effects on memory, thinking and reaction time. Simple things like safety in crossing the road, or cooking, or handling sharp objects could become important.
    3. In other words when initiating any medication the whole process of capacity and consent needs to be done.

Tab 2 content.

I visit a patient FTF, who was not previously known to me at their care home. The adult male patient, has an intellectual disability. The basic clinical details are that the patient displays very challenging behaviours e.g. biting, grabbing, slapping himself, running away from supervision and running across roads in a reckless way. I discover that the patient is prescribed moderate doses each of two antipsychotics, one antidepressant, sodium valproate (when he is not epileptic) and regular diazepam (an anxiolytic) twice daily.

  1. Do I know which doctor(s) prescribed which medications and what was their reasoning? I need to read the records carefully.
  2. I recognise that there is a high probability that the prescribing I have inherited involves polypharmacy which seems quite serious.
  3. I recognise that some or all of the medications may be part of unlicensed prescribing.
  4. I recognise that there will be a need to know whether the patient can consent to such a cocktail of medications, especially when there is a diagnosis of moderate to severe intellectual disability.
  5. I must consider whether the patient is behaviourally toxic from such a cocktail of medications.
  6. In this situation I should seek advice from a pharmacist.

[GMC Prescribing Guidance (full): https://bit.ly/GMCRxFullGuidance.]

  • Paragraphs 20-26 indicate that a face-to-face consultation is most appropriate to assess this complex patient and make sure you have sufficient information to prescribe safely.
  • Paragraphs 41-44 covers assessing the patient’s capacity to make decisions about their care and treatment. This is important given their intellectual disability.
  • Para 46: is specific about consulting team members and pharmacists where important to do so.
  • Paragraph 59 advises caution when prescribing medicines that can be abused/misused, like diazepam and opioids, without access to full medical records.
  • Paragraph 65 cautions against prescribing sedatives like diazepam for convenience rather than clinical need.
  • Paragraphs 76-78 are relevant if considering recommending changes to prescribing – “you must be satisfied any colleagues you ask to prescribe have sufficient knowledge of the patient and medicines.
  • Paragraphs 94-97 emphasise the importance of reviewing and reassessing the need for medicines being prescribed, especially in vulnerable patients.
  • Paragraphs 98: “You are responsible for any prescription you sign, including repeat prescriptions for medicines initiated by colleagues, so you must make sure that any repeat prescription you sign is safe and appropriate. You should consider the benefits of prescribing with repeats, and where possible, reduce repeat prescribing.” [emphasis added]

[GMC Prescribing Guidance (full): https://bit.ly/GMCRxFullGuidance.]

  1. The GMC is clear in para 98 of their guidance that my duty in repeat prescribing is to make sure that any repeat prescription I sign (authorise), is safe and appropriate.
  2. This guidance means that I cannot be comfortable that some other doctor prescribed it and I am ‘only repeating’ the prescription.
  3. I need to establish whether the patient has consented to the combination of medications to the previous prescribers.
  4. I cannot simply stop all medications instantly if I think it may be causing risk of toxicity. I need to evaluate the risk first.
  5. If there are serious risks to the patient, I will be obliged to inform the patient and reassess his capacity to consent to some sort of graded reduction.
  6. I will need to consult with a pharmacist and my psychiatrist colleagues about this situation in accordance with para 46 of the GMC’s prescribing guidance.

In summary, as a licenced doctor I have a duty to review the clinical appropriateness of the patient’s medications, raise any concerns, ensure changes are handled carefully by doctors with appropriate expertise, and support deprescribing if indicated.

Tab 2 content.

The power of medications

Medicines are powerful ‘chemicals’. How? A few milligrams – thousandths of a gram – can have powerful effects on the body’s organs. 20 mg of citalopram is 7 ten thousandths of an ounce.  The body of an average female of 70kg(154lb, or 11 stone) contains 31 litres (or 8 gallons of water). On ingesting 20mg of citalopram about 16 mg will enter the blood stream and be diluted by the 8 gallons. The 16 mg represents what is roughly known as ‘bioavailability‘, but that’s not the full story. Only a tiny fraction (hard to calculate) will actually get into the brain because it has to cross what is known as the blood brain barrier (BBB). In other words the BBB acts as a filter of sorts. But the concentration in the blood is increasing for the first 4 hours, and then half of the citalopram would be eliminated by the body over the next 35 hours (interrupted of course by the next morning’s dose). The point is that we cannot consider 16mg of the 20mg of citalopram remaining at a constant level in the blood. Whilst the concentration is fluctuating, the BBB is doing its job to ‘filter’ out much of the medication. The point is that only a very tiny amount of the drug enters the brain to do its job. That means the tiny amount is very powerful. [This is a  rough and ready explanation so may bear some inaccuracies.]

Many prescribers do not consider the power of the ‘pen’ when they write that prescription. They should. See below where I have tabulated and added ‘elimination half-life’ – the time it takes for blood concentration to fall by half of its peak.

MedicationBioavailabilityElimination Half-Life
Citalopram80%35 hours
Fluoxetine72%1-3 days (acute), 4-6 days (chronic)
Sertraline44%26 hours
Quetiapine83%6 hours
Risperidone70%3 hours (parent compound), 20 hours (active metabolite)
Clopixol (Depot)55-70%19 days (depot injection)
Clopixol (Tablets)49%~20 hours
Clozapine27-50%6-8 hours (parent compound), 8-12 hours (metabolites)
Diazepam93-100%20-100 hours (parent compound), 36-200 hours (metabolites)
Lorazepam85-90%10-20 hours
Temazepam96%8-22 hours

The power of a medication should also be considered in terms of its side effects. This is because side-effects can influence or limit the quality or enjoyment of life i.e. side-effects have a power over the individual. Some side-effects can impair reaction times and information processing. The latter would be important and often imperceptible to someone who has to drive a vehicle, cross roads or operate machinery of any kind. Some side-effects may affect sexual functions. 

If a medication has a long half-life, that means that it can build up and linger for a longer time in the body. A medication with a high side-effect profile and a long elimination half-life can be expected to cause more problems when it causes side-effects.

Some medications can cause dependence and can then lead to withdrawal effects.

The fundamental principles

The GMC’s guidance on prescribing April 2021 (updated March 2022), is an important document for all doctors and even patients. It is very easy to read. Little medical knowledge is needed to understand what it says. In no way is the guidance, ‘just guidance’ which can be ignored. Why? Because it creates important duties of care. Doctors who are caught breaching the guidance and get into bother, can expect a rough time at the GMC. Depending on seriousness of some breach could be warned, suspended, conditions put on their licence or be struck off. Note the following principles taken from the guidance.

  1. Patient – This is the guiding principle running throughout the guidance. Doctors must prioritise patient safety and avoid harm in all prescribing decisions.
  2. Shared decision-making – Doctors should engage in dialogue with patients, explain treatment options, and obtain informed consent before prescribing.
  3. Responsibility – Doctors are accountable for prescriptions they sign and must only prescribe when competent to do so.
  4. Caution – Extra care should be taken when prescribing medications with potential for misuse/abuse or other elevated risks.
  5. Information sharing – Prescribers must enable information sharing with other healthcare providers involved in the patient’s care.
  6. Record keeping – Adequate and accurate records must be kept detailing reasons for prescribing decisions.
  7. Reviewing medications – Doctors have a duty to regularly review medications, especially for vulnerable patients, to ensure continued appropriateness.
  8. Raising concerns – Doctors must protect patients by questioning unsafe practices and raising concerns appropriately.

The above are only headlines that extract principles. Hence, there are no detailed explanations of each. The guidance is essential reading and expands on each of the above in various parts. I suggest that the eight principles I have extracted are a good way of approaching every act of prescribing.

Basic considerations when prescribing

  1. Do I know the patient well enough i.e. knowledge from all reasonable sources.
  2. Do I have enough evidence to make a diagnosis?
  3. Am I compliant with the framework document Good Medical Practice? [It is a framework because it draws on 34 other important guidance documents].
  4. Am I competent to prescribe for this patient with ‘this condition’? This includes sound knowledge of all aspects of the medication(s).
  5. How sure am I that I need to prescribe – or are there any alternatives to prescribing?
  6. Is the treatment licenced to treat the patient’s condition?
  7. What if I am unsure about diagnosis – should I encourage the patient to try a medication and see if it works?
  8. Is the patient of capacity to consent?
  9. Have I disclosed all relevant information? Material risks as per Montgomery 2015 become important.
  10. What if the treatment doesn’t work – what’s next?

There are many more considerations. I have only listed a few.


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