Characteristics of hospital-treated intentional drug overdose in Ireland and Northern Ireland

OBJECTIVES This study compared the profile of intentional drug overdoses (IDOs) presenting to emergency departments in Ireland and in the Western Trust Area of Northern Ireland between 2007 and 2012. Specifically the study aimed to compare characteristics of the patients involved, to explore the factors associated with repeated IDO and to report the prescription rates of common drug types in the population. METHODS We utilised data from two comparable registries which monitor the incidence of hospital-treated self-harm, recording data from deliberate self-harm presentations involving an IDO to all hospital emergency departments for the period 1 January 2007 to 31 December 2012. RESULTS Between 2007 and 2012 the registries recorded 56,494 self-harm presentations involving an IDO. The study showed that hospital-treated IDO was almost twice as common in Northern Ireland than in Ireland (278 vs 156/100,000, respectively). CONCLUSIONS Despite the overall difference in the rates of IDO, the profile of such presentations was remarkably similar in both countries. Minor tranquillisers were the drugs most commonly involved in IDOs. National campaigns are required to address the availability and misuse of minor tranquillisers, both prescribed and non-prescribed.

P-glycoprotein inhibition as a strategy to increase drug delivery across the blood-brain barrier: focus on antidepressants

Depression is among the leading causes of disability worldwide. Currently available antidepressant drugs have unsatisfactory efficacy, with up to 60% of depressed patients failing to respond adequately to treatment. Emerging evidence has highlighted a potential role for the efflux transporter P-glycoprotein (P-gp), expressed at the blood-brain barrier (BBB), in the aetiology of treatment-resistant depression. In this thesis, the potential of P-gp inhibition as a strategy to enhance the brain distribution and pharmacodynamic effects of antidepressant drugs was investigated. Pharmacokinetic studies demonstrated that administration of the P-gp inhibitors verapamil or cyclosporin A (CsA) enhanced the BBB transport of the antidepressants imipramine and escitalopram in vivo. Furthermore, both imipramine and escitalopram were identified as transported substrates of human P-gp in vitro. Contrastingly, human P-gp exerted no effect on the transport of four other antidepressants (amitriptyline, duloxetine, fluoxetine and mirtazapine) in vitro. Pharmacodynamic studies revealed that pre-treatment with verapamil augmented the behavioural effects of escitalopram in the tail suspension test (TST) of antidepressant-like activity in mice. Moreover, pre-treatment with CsA exacerbated the behavioural manifestation of an escitalopram-induced mouse model of serotonin syndrome, a serious adverse reaction associated with serotonergic drugs. This finding highlights the potential for unwanted side-effects which may occur due to increasing brain levels of antidepressants by P-gp inhibition, although further studies are needed to fully elucidate the mechanism(s) at play. Taken together, the research outlined in this thesis indicates that P-gp may restrict brain concentrations of escitalopram and imipramine in patients. Moreover, we show that increasing the brain distribution of an antidepressant by P-gp inhibition can result in an augmentation of antidepressant-like activity in vivo. These findings raise the possibility that P-gp inhibition may represent a potentially beneficial strategy to augment antidepressant treatment in clinical practice. Further studies are now warranted to evaluate the safety and efficacy of this approach.

Strategies to prevent potentially inappropriate prescribing and adverse drug reactions in older patients

INTRODUCTION: Potentially inappropriate prescribing (PIP) is a major contributor to adverse drug reactions and overall increased healthcare costs. The aim of this thesis was to identify, develop and implement strategies with the potential to prevent PIP and ADRs in older patients. METHODS: A systematic review of the qualitative literature (Meta-synthesis); A qualitative study in Irish hospitals; A randomised controlled trial (RCT) to assess the impact of an online educational module on doctors’ prescribing knowledge and confidence; Exploration of the potential for a frailty index score to enable doctors identify patients at increased risk of PIP and ADRs; Exploration of the potential for the SHiM tool to enable doctors to optimise prescribing for older patients. RESULTS: The meta-synthesis identified four key concepts: (i) Desire to please the patient; (ii) Feeling of being forced to prescribe; (iii) Tension between experience and guidelines; (iv) Prescriber fear. Similar themes also emerged from the qualitative study. In the RCT, the online educational module resulted in a highly significant 22% difference in test scores between intervention and control groups. The studies exploring the frailty index score showed a significant positive relationship between a patient’s frailty status and their likelihood of experiencing PIP/ADRs. Patients above a frailty threshold of 0.16 were at least twice as likely to experience PIP/ADRs. SHiM was found to be a useful tool in terms of reconciling patients’ medications. However, the evidence for it being capable of preventing clinically relevant adverse events was poor. CONCLUSION:Qualitative research in this thesis has proposed novel theories relating to the causative factors of PIP in older patients. In doing so, it has identified several areas for intervention and laid down a road map for future research.