Catia Marzolini then presented some interesting information showing the drug- drug interaction profiles of some of the antiretroviral drugs with 700 comedications, demonstrating that for many of these combinations there was no interaction.
Catia Marzolini is also a member of the Liverpool HIV drug-drug Interactions website, and the results of a global search of this website (www.hiv-druginteractions.org) from 2017 were used to identify the most commonly searched drugs:
#10 – DDIs with statins
#9 – DDIs with antidepressants
#8 – DDIs with PrEP and Chemsex
#7 – DDIs with antihypertensives
#6 – DDIs with metformin
#5 – DDIs with PPIs, antacids and mineral supplements
#4 – DDIs with rifampicin
#3 - DDIs with corticosteroids
#2 – DDIs with anticoagulants
#1 – DDIs with antiplatelet agents
Very detailed information was presented for all of these DDIs, which included the mechanistic aspects of the interaction, and any available pharmacokinetic/pharmacodynamic data. The potential outcome of each DDI was discussed outlining whether the risk was drug toxicity or treatment failure of the antiretroviral drug and/or the co-administered drug, and recommendations regarding clinical management strategies were included.
One limitation of this data analysis and presentation was that drugs with QT risk, contraceptives, Hepatitis C drugs and Cancer drugs were not included or discussed.
One of my key learnings from the session related to the use of antidepressants in patients with HIV infection. Data was presented from a study by Cattaneo D et al, published in The World Journal of Biological Psychiatry in 2018. This study compared antidepressant levels in HIV-infected vs HIV-negative individuals. The study identified that a larger proportion of HIV-infected patients were found to have subtherapeutic antidepressant levels compared to uninfected individuals, suggesting deliberate lower dosing of antidepressants as clinicians fear DDIs with antiretroviral drugs. Since depression is an exceptionally common comorbidity in patients with HIV infection, this information is of concern since it implies that depression is not being optimally managed in patients with HIV infection.
Another useful learning from this presentation was the awareness of a new website covering cancer drug interactions, which has been launched by The University of Liverpool and Radboud University: www.cancer-druginteractions.org. This should hopefully prove to be a useful additional online drug interactions database.
In my role as HIV/Sexual Health Consultant Pharmacist I frequently refer to drug interaction databases in order to obtain information and provide advice and recommendations to both health care professionals and patients. I found the global top 10 DDI list interesting, but not reflective of the DDIs that I investigate. The presentation did however highlight the need to continually check whether any new data is available when being asked questions about DDIs, as the data is continually evolving. One of the most important reminders from this presentation was that DDIs are practically unavoidable in the management of HIV infection, but largely manageable. However it is important to consider DDIs when selecting an antiretroviral regimen, when changing an antiretroviral regimen, when prescribing any additional medications for a patient and also when ceasing any medications that a patient may be taking.
Searchable online drug interaction databases can be valuable tools to recognise and manage unwanted DDIs. Additional information obtained from University of Liverpool HIV Drug Interactions Exhibition at HIV Glasgow 2018, identified that Oceania currently forms 5% of the global usage of www.hiv-druginteractions.org website. One of the current limitations of this website is that it does not include some of the medications commonly prescribed in Australia.
Through my attendance at this Conference I was able to meet with the University of Liverpool HIV drug interactions team, who offered me the option (available to all clinicians) to submit requests for medications to be added to the database. As a consequence, one way that I will change my practice is to submit requests for drugs commonly prescribed in Australia to be added to the database, with the aim of increasing the website's applicability to the Australian setting, thereby ultimately improving patient medication efficacy and safety.
Finally, the cancer drug interactions website will be a new website that I will be accessing in the future. Hopefully it will provide helpful information and advice in relation to the complex area of DDIs between antiretroviral drugs and drugs used in the treatment of cancer.
Author bio:
Fiona trained as a pharmacist in UK prior to moving to Australia in 1997. She has been working as a clinical pharmacist in the area of HIV/Sexual Health on the Gold Coast since 1998. She was involved in a pilot of pharmacist prescribing for patients with HIV infection in 2009-2010. She is contacted for advice by health professionals external to the Gold Coast, and has provided advice in relation to adults, adolescents and children with HIV infection.
