[6] He is a co-leader of the Front Line COVID-19 Critical Care Alliance (FLCCC), which has misleadingly advocated for the anti-parasitic drug ivermectin to treat COVID-19 against the advice of leading health agencies.
[13] Marik did a critical care fellowship in London, Ontario, Canada, and subsequently has worked in the United States in teaching hospitals since 1992.
[18] In 2011, an international committee assembled by the main thoracic and respiratory national societies published guidelines for the diagnosis and management of idiopathic pulmonary fibrosis.
The guidelines' section on the treatment of complications relied in part on the results of Marik's 2001 research on the association of gastric reflux and aspiration.
In its section of supportive therapy recommendations, the committee based its concept on blood product administrations partly on research performed by Marik and W. Sibbald in 1993.
[20][non-primary source needed] In 2017, Marik won the American College of Physicians award for outstanding educator of residents and fellows.
[31] Marik's findings received attention on social media and National Public Radio, but drew criticism from the wider medical community for being science by press conference.
[32][33][9] ER doctor Jeremy Faust was one of a number of skeptics of the results, noting the low reliability of the study design and potential for bias.
[5] Marik is a co-founder of the Front Line COVID-19 Critical Care Alliance (FLCCC), a group of physicians and former journalists formed in April 2020 that advocates for ineffective COVID-19 treatments, including hydroxychloroquine, the anti-parasitic drug ivermectin, and intravenous vitamin C.[6][7][8][36][37] Marik was lead author of a journal article on the efficacy of ivermectin as a COVID-19 treatment, which had been provisionally accepted for publication by a Frontiers Media journal in early 2021, but which was subsequently rejected on account of what the publisher said were "a series of strong, unsupported claims based on studies with insufficient statistical significance" meaning that the article did "not offer an objective [or] balanced scientific contribution to the evaluation of ivermectin as a potential treatment for COVID-19".
[38] In November 2021, the Journal of Intensive Care Medicine retracted a paper written by Marik and others associated with the FLCCC, including Pierre Kory.
The retraction was triggered when it was found the paper misreported the mortality figures of hospitalized patients treated with MATH+, falsely making it appear to be an effective treatment.