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KEY WORDS: drug selection, interindividual variation, monitoring therapy, rational prescribing
Prescribing is a complex task requiring:
* diagnostic skills
* knowledge of medicines
* an understanding of the principles of clinical pharmacology
* communication skills
* appreciation of risk and uncertainty.
The accumulation of clinical trials' data on modern therapies might have been expected to provide sufficient evidence to support most clinical decisions. In fact, clinicians prescribe in varied circumstances, often in the absence of evidence, and rational prescribing decisions must be based on knowledge interpreted in the light of many other factors.
Rational prescribing
Rational prescribers should attempt to:
* maximise clinical effectiveness
* minimise harms
* avoid wasting scarce healthcare resources
* respect patient choice.
Rational prescribing normally follows a logical sequence from diagnosis to follow-up (Fig 1).
Diagnosis
Prescribing decisions should be based on the primary diagnosis and relevant secondary diagnoses. Ideally, these should have been made or confirmed by the prescriber who will take responsibility for the effects of treatment. Appreciating that diagnoses are made with varying degrees of uncertainty is important when assessing the benefit-to-harm balance of treatment. For instance, antibiotics are often prescribed on the basis of presumed antibacterial sensitivity with the expectation of significant benefit. However, this can expose the recipient to harm without the prospect of cure.
Prognosis
The prognoses of the primary and secondary diagnoses will affect rational treatment choices. A secondary diagnosis with a poor prognosis, such as lung cancer, will severely limit the benefits of treating a primary one, such as hypercholesterolaemia. On the other hand, the excellent prognosis of influenza in a healthy adult limits the potential benefits of antiviral therapy.
Goals of therapy
Goals of therapy may include:
* curing a disease (eg cancer, infection)
* relieving symptoms without affecting the underlying condition (eg headache, diarrhoea)
* combining two outcomes (eg inflammatory bowel disease and arthritis)
* long-term prevention (eg hypertension, osteoporosis)
* replacing deficiencies (eg hypothyroidism), and occasionally
* therapeutic trials to aid diagnosis.
Treatment selection
Prescribers are commonly faced with more than one choice of treatment, including non-pharmacological therapies or no treatment. For example, the management of arthritis might include reassurance, simple analgesia, physiotherapy, non-steroidal anti-inflammatory drugs, disease-modifying antirheumatic drugs, intra-articular steroids or surgery.
Monitoring
Each prescription constitutes...