3.4.1.3 Tailored prescribing and the individual risk benefit appraisal

Building the individual profile

• Treatment history records past drugs, doses, adequacy of trials, adherence and response, and separates non-response from intolerance.

• Assess age, organ function, pregnancy, genotype, smoking and interactions, and note how comorbidity raises the stakes, such as antimuscarinics in cognitive impairment.

Absolute and relative risk

Give absolute as well as relative risk. Doubling from 1 to 2 per 1,000 adds one event per 1,000, whereas doubling from 1 to 2 per 10 adds one per 10.

Overdose risk and the fatal toxicity index

• The fatal toxicity index measures a drug's lethality in overdose as poisoning deaths per million prescriptions.

• Its denominator is prescriptions, not doses or overdoses.

• Tricyclic antidepressants such as dosulepin and amitriptyline score as more dangerous than selective serotonin reuptake inhibitors.

• The index is biased by prescribing patterns, because clinicians steer high-toxicity drugs away from patients at high risk of overdose.

• It therefore reflects who receives a drug as well as the drug's inherent lethality.

• Where overdose risk is high, limit supply without leaving gaps in access.

Consent and capacity

• A risk is material if a reasonable person in the patient's position would find it significant, or if it is known to matter to this patient (Montgomery, 2015).

• Capacity is decision-specific and time-specific: under the Mental Capacity Act 2005, the person must be able to understand, retain, use or weigh, and communicate the decision.