Drug history and drug development

Drug history

A patient’s drug history is a crucial component of the clerking process, as drug effects account for a significant
proportion of hospital admissions, and potential drug interactions and adverse events are crucial to foresee.

A complete list of the names and doses of prescribed drugs taken by the patient (noting the proprietary and the generic name, e.g. Viagra and sildenafil, respectively) and any other medications or supplements they may have bought themselves over the counter at a pharmacy should be documented.

Women often forget the contraceptive
pill and hormone replacement therapy, and should be sensitively questioned about these. NSAIDs and paracetamol are often taken by patients with arthritis and should be specifically asked about. Make sure to note how often the drugs were taken, and at what times.

If presented with numerous bottles and packets of tablets, it is important to ensure that they all belong to the patient, and not the partner of the patient, or
to someone else.

Always ask the patient if they are taking
all their medicines as prescribed.

Occasionally it is useful to know what drugs have been taken in the recent and distant past; for example, monoamine oxidase inhibitors should be stopped at least 3 weeks prior to starting a different antidepressant therapy.

Previous adverse reaction to drugs, and to non-drug products such as latex, is essential to ascertain. Explore
what happened to the patient, and what was done about it. A simple upset stomach and loose stools just for one
day after taking penicillin previously is an acceptable side-effect, and is not grounds for choosing another
antibiotic when treating a penicillin-sensitive infection in the future.

Widespread cutaneous rash and difficulty breathing which required adrenaline and hospital admission is a genuinely worrying adverse effect of a penicillin, and any such drug should be clearly avoided in the future as this was an allergic drug reaction.

Allergy to drugs should be clearly marked in the patient’s notes and drug charts.

Family history of adverse drug reactions is usually confined to the anaesthetic history, where the concern is largely in relation to the muscle relaxing drugs, particularly suxamethonium.

A history of recreational or illicit drug use is an important but sensitive issue to approach. One must use discretion when questioning the patient.

A history of smoking should also be established.

Knowledge about any hepatic or renal disease and general health problems is important when it comes to management and prescribing, as are specific considerations, such as not prescribing aspirin in peptic ulcer disease, or oestrogen to patients with oestrogendependent cancers. These aspects are usually brought to light in the rest of the history taking.

Note

The salient points of the drug history are:

  1. current and previous drugs and their doses
  2. adverse drug reactions and allergies
  3.  family history of allergies
  4. recreational drug use
  5. existing renal or hepatic and general disease.

Drug development

Hundreds of thousands of substances have been produced by the pharmaceutical industry over the past 50
years, though very few ever get past preclinical screening, and fewer than 10% of these survive clinical assessment.

There are four clinical stages a potential drug goes through as part of the assessment of its pharmacokinetics and pharmacodynamics: efficacy, dose–
response relationship and safety.

The five stages of drug development and monitoring

We have:

  • Preclinical phase
  • Phase 1
  • Phase 2
  • Phase 3 and
  • Phase 4

1. Preclincal: here, we check the pharmacology and toxicology of the investigational drug using in vitro means in the laboratory. Animal models are used.

2. Phase 1: this phase is a clinical phase as healthy human and/or patients are used for the trail. Here, we evaluate the investigational drug’s metabolism, bioavailability, safety

3. Phase 2: Initial treatment studies are done here. We evaluate the efficacy of our trial drug. Here, we use small numbers of patients

4. Phase 3: Large randomized controlled trials are done here. Comparing new to
old treatments. Safety and efficacy are evaluated here.

5. Phase 4: Post-marketing surveillance. Long-term safety and rare events are evaluated here. This phase is yellow card scheme. All patients who need the drug are used here for the evaluation.

Phase 4 can be regarded as an ongoing phase, where drugs are monitored once licensed for general use. By this stage, the efficacy and dose–response relationship are known, although the side-effect profile is often incomplete, and information is gathered on these ‘adverse reactions’ which are due to, or likely due to new drugs.

In the UK this is known as the yellow card scheme. The British National Formulary (BNF) contains detachable yellow cards, which medical staff complete, documenting adverse drug reactions in their patients, which can then be forwarded to the Medicines Control

Agency. The Medicines Control Agency collates these data, and uses them for surveillance of common or severe adverse effects. The data are publicized in future copies of the BNF, or used in the reassessment of certain drug licences.

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