SPECIALIST PHARMACOLOGICAL & BIOCHEMICAL INTERVENTIONS

RAPID DIAGNOSIS OF OPIOID DEPENDENCE WITH NALOXONE EYE-DROPS

New patients presenting for treatment of opioid misuse are routinely subjected to a lengthy assessment process to determine whether they are dependent on opiates or are casual users. If dependence is diagnosed, opioids may be prescribed on a regular basis for stabilisation prior to detoxification. However, the provision of a regular prescription to casual users may contribute to the development of dependency. Accurate diagnosis of the dependent state is therefore essential, but the current lengthy process tends to deter people from seeking help. Additionally, the use of urine screeing for opiates indicates only recent use of drugs, rather than prolonged exposure.

Instillation of eyedrops containing naloxone into one eye of an opioid-dependent subject causes, a short time later, pupil dilatation (mydriasis) in that eye only, without inducing a 'systemic' withdrawal syndrome (Bellini et al, 1982). Mydriasis is not seen if the same test is carried out in healthy, unmedicated subjects (Ghodse, 1986) or in normal subjects given an opioid prior to minor orthopaedic surgery (Creighton & Ghodse, 1989), implying that pupil dilatation indicates prolonged exposure to opiates, as opposed to isolated or intermittent use.

The opiate addiction test, using unilateral instillation of conjunctival naloxone hydrochloride and pupillometry, is a simple, reliable and accurate method of diagnosing opioid dependence. Sensitivity on the first clinic visit is enhanced by the use of binocular infrared electronic pupillometric equipment, but is not essential to institute the test as a routine component of assessment. Evaluation in the clinical situation has demonstrated a 100% specificity of the test and an 81% sensitivity (Ghodse H et al, 1999). A patient with a positive response to the opiate addiction test is thus known to be opioid-dependent; this may be determined at the initial appointment and treatment instituted immediately. However, a negative result does not provide unequivocal proof that the patient is not dependent on opiates; in this situation, the patient should be re-tested and a subsequent positive result should be taken to indicate that he or she is in fact opioid-dependent and should be treated accordingly (Ghodse H et al, 1999).

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The above information is copyright of Dr Bruce Trathen MBBS MRCPsych (2006). ISBN 0-9545164-0-0. The author grants permission for these guidelines to be downloaded, copied and distributed freely, but does not grant permission for their sale.