07 - UK DVLA

UK DVLA

Psychotropic drugs in special conditions CHAPTER 13 In regards to methadone, doses of up to 80mg a day generally give plasma levels below the UK legal limit.61 The legal limits listed here apply only to those who are lawfully prescribed the drug in question – the driver may be subject to prosecution if it can be proved the drugs were taken illicitly. Other medicines Many psychotropics can impair alertness, concentration and driving performance. Medicines that block H1, α1-­adrenergic or cholinergic receptors may be particularly problematic. Sedative antihistamines used in mental health conditions (promethazine, diphenhydramine) very probably impair driving ability.62 Effects are particularly marked at the start of treatment and after increasing the dose. Drivers must be made aware of any potential for impairment and are advised to evaluate their driving performance at these times. They must stop driving if adversely affected.63 The use of alcohol will further increase any impairment. Some antipsychotics and antidepressants lower the seizure threshold. In the UK, the DVLA advises this is taken into consideration when prescribing for a driver. Medication-­induced sedation Many psychotropics are sedating. The more sedating a medicine is, the more likely it is to impair driving ability. Other medicines, either prescribed or bought over the counter, may also be sedative and/or affect driving ability (e.g. antihistamines5). One study found that 89% of patients taking other psychotropics in addition to antidepressants failed a battery of ‘fitness to drive’ tests.64 Since the degree of sedation any individual will experience is very difficult to predict, patients prescribed sedating medicines should be advised not to drive if they feel sedated. In the UK it is the responsibility of the driver to ensure they are fit to drive. UK DVLA Duty of the driver In the UK it is the legal responsibility of the licence holder or applicant to notify the DVLA of any medical condition that may affect safe driving. A list of relevant medical conditions can be found in the DVLA assessing fitness to drive guide.65 Table 13.3  Benzodiazepines concentration in normal dosing and the UK legal limit. Drug/daily dose Range of concentrations reported Legal limit Clonazepam 0.5–6.0mg52,53 5–80mcg/L 50mcg/L Diazepam 5–30mg54 50–1000mcg/L 550mcg/L Flunitrazepam 0.5–2.0mg55,56 10–20mcg/L 300mcg/L Lorazepam 1–4mg57,58 10–70mcg/L 100mcg/L Oxazepam 15–30mg59 250–600mcg/L 300mcg/L Temazepam 10–20mg60 200–900mcg/L 1000mcg/L