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Alcohol
Cannabis
Stimulants
Prescribed Drugs
The
Inexperienced Driver
Publications
Principles
There is limited understanding of the role of drugs in the causation of traffic collisions. There is no doubt that large numbers of people drive after ingesting drugs from all sources: prescribed, over-the-counter, recreational and illicit. In various studies within Australia and overseas, drugs have been found in up to 10 - 15% of people who have died as a result of road trauma. However, given the high incidence of drug use within the community the correlation between drug use and road trauma remains clouded. Major problems There are major problem to be faced in attempting to find a correlation between drug consumption and road trauma.
Can we prove that a drug has been consumed?
This requires analysis of a body fluid to identify the drug. There are a large number of potential drugs that could be screened, and many of the drugs of interest may only be present in minute quantities whilst having significant effects. It is economically impossible to screen for all possible psychoactive drugs, so that our knowledge is patchy at best.
Can we determine much drug has been consumed?
Whilst it may be possible to detect a drug, it may not be possible to determine the quantity present. The very potent synthetic narcotics and stimulants typify the problem. It is sometimes impossible to quantify a substance even if its presence can be demonstrated.
Could the amount of drug detected produce impairment?
Does this substance cause impairment of human skills?
If so, is such impairment universal or idiosyncratic?
Does the impairment occur
in normal dosages or only when used in
excess?
Anti-anxiety drugs
The benzodiazepine group of drugs includes minor tranquillisers, sedatives, anticonvulsants and hypnotics. Representative members of the group are diazepam, oxazepam, nitrazepam and flunitrazepam. These drugs have largely taken the place of the barbiturates in the treatment of anxiety and insomnia because of their efficacy and safety even with overdose.
Different members of the class depress the central nervous system to varying degrees and in qualitatively different ways. Some are better at relieving pathological anxiety and agitation and are classified as tranquillisers. Others are more sedating and hence are used to treat insomnia. Some members of the group are primarily used in epilepsy as anticonvulsants. There is no sharp distinction between any of these effects and higher doses of any of the benzodiazepines may induce sedation and coma.
The serum level of each of the benzodiazepines is related to the degree of impairment in the laboratory. There is an increased risk of personal injury crashes among drivers using anti-anxiety drugs compared with the rest of the population and this is exacerbated by alcohol. There is a hangover effect and a small dose of alcohol the following day can potentiate the effect. There is a decrement in tasks requiring vigilance at low doses and tolerance is only occasionally noted. The opposite effect, exaggerated impairment, has also been documented.
The risk of collision is doubled for patients taking benzodiazepines especially in the first two weeks of treatment. The ICADTS working group concluded that patients should be warned not to drive in the first two weeks of treatment. However, not all research has found an association between sedative use and collision risk. Clinically anxious patients are also poor drivers. in the first place and treatment with benzodiazepine tranquillisers will improve clinical anxiety. There is no evidence it improves driving ability.
Psychoactive Medication
The untreated psychiatric patient is a potentially hazardous driver either because of the underlying illness and the consequent disorder of the mind, or of the associated psychomotor impairment. Once stabilised on medication, patients are better on their medication and a greater risk without it. There is some question about the generality of this conclusion as it has been based primarily on subjective clinical judgment without inadequate research backing.
Different members of each class of psychoactive medication have quite different effects on driving. For instance, the tricyclic antidepressants are quite impairing of driving skill, whilst the selective serotonin reuptake inhibitor (SSRI) antidepressants have lesser effect on driving and little or no interaction with alcohol.
Opioid Analgesics
The opiate drugs - heroin, methadone, codeine and related compounds - are used for pain relief and the suppression of cough. They have a high addiction potential. Acute sedation and impairment is observed in a dose-related manner and there is a deleterious interaction with alcohol, although the effects are slight compared with alcohol. Methadone is used for the long-term maintenance therapy of narcotic addicts and is not associated with an increase in collision risk after the initial stabilisation period.
Minor Analgesics and Anti-arthritics
There are few central side effects of the common minor painkillers (aspirin, paracetamol) or of the non-steroidal anti-inflammatory agents that are used for the treatment of arthritis.
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