Módulo 1 – Curso pós-graduado – VIH e Envelhecimento

Drug-drug Interactions and Polypharmacy in Older HIV Persons

Polymedication and drug metabolism in aging patients

Mensagens-chave

  • As a consequence of antiretroviral therapy, it is expected that most patients with HIV infection / acquired immune deficiency syndrome (AIDS) may became older than 50 years in the next 20 years;
  • The prevalence of comorbidities is higher in HIV patients compared with HIV-negative individuals, especially for older age groups. The polypharmacy is also more common in people with HIV infection.
  • Physiological changes associated to age may affect the pharmacokinetics and pharmacodynamics of drugs absorption, distribution, metabolism and elimination – and contribute to higher toxicity and lower effectiveness, mainly for patients older than 60-70 years.
  • Polypharmacy and pharmacokinetic changes in elderly tend to increase plasma levels of the drugs, also contributing to greater inter-individual variability and increased risk of drug interactions.
  • In this context, the choice of antiretroviral therapy is more complex as a result of comorbidities and associated co-medication, and there is still little information on the pharmacokinetics of antiretroviral drugs.
  • It is important to assess the risk of interactions, especially in patients with HIV and other comorbidities, and to carefully consider the introduction, modification or suspension of a drug.
  • There are some tools to support the assessment of interactions:
    – The website of the University of Liverpool allows the identification of interactions between antiretroviral drugs and other drugs or substances of abuse.
    – The Medscape website also allows to identify interactions be- tween non-antiretroviral drugs.
  • Some therapeutic regimens namely those that include ritonavir have an increased risk of interactions. On the other hand, the use of integrase inhibitors shows less risk of interactions.
  • Em alguns indivíduos, existem polimorfismos genéticos que podem determinar o aumento dos níveis plasmáticos de alguns fármacos e aumento da toxicidade.
  • Nos indivíduos coinfetados por vírus da hepatite B (VHB) ou VHC, o risco de hepatotoxicidade é maior nos estádios mais avançados. Neste caso, os fármacos mais seguros são aqueles que não são metabolizados pela via do CYP450, nomeadamente os inibidores da integrase.
  • O tratamento do indivíduo idoso coinfetado por VIH e VHC com ledipasvir/sofosbuvir deve ser cautelosamente monitorizado, principalmente quando há coadministração com ritonavir e TDF.
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