1. pregnant, planning to become pregnant, or breastfeeding 2. opioid medications: * any use within last 15 days, as reported by the patient * during the trial 3. a positive urine test for opioids (only for the first 16 participants) 4. history of alcohol, opioid or other substance misuse 5. participation in another interventional clinical trial in the last 30 days or planned during the trial period 6. confirmed me/cfs or fm existing prior to sars-cov-2 infection 7. allergy to naltrexone or medication components 8. acute hepatitis, liver failure, or severe kidney failure. 9. current or recent use of naltrexone in the last 30 days 10. the participant is not an ideal candidate for the study, in the opinion of the investigator, for any other reason (ie. personal or logistic, medication, condition, etc.) that could impact the participant's safety or the results of the study. opioid washout period: potential participants who are currently taking opioid medications who wish to enrol the study will be instructed they can stop taking opioid medications for 15 days before continuing the screening process. they will be instructed that they should speak with their family doctor before stopping any prescribed medications. positive urine test for opioids: as regular use of opioid medications is an exclusion criterion, we will do a quality control check with the first 16 participants to test for the presence of opioids in their urine. any participants with a positive test, will be excluded from the study, and such finding will be discussed at the trial steering committee or dsmb for potential trial modification.

1. pregnant, planning to become pregnant, or breastfeeding 2. opioid medications: * any use within last 15 days, as reported by the patient * during the trial 3. a positive urine test for opioids (only for the first 16 participants) 4. history of alcohol, opioid or other substance misuse 5. participation in another interventional clinical trial in the last 30 days or planned during the trial period 6. confirmed me/cfs or fm existing prior to sars-cov-2 infection 7. allergy to naltrexone or medication components 8. acute hepatitis, liver failure, or severe kidney failure. 9. current or recent use of naltrexone in the last 30 days 10. the participant is not an ideal candidate for the study, in the opinion of the investigator, for any other reason (ie. personal or logistic, medication, condition, etc.) that could impact the participant's safety or the results of the study. opioid washout period: potential participants who are currently taking opioid medications who wish to enrol the study will be instructed they can stop taking opioid medications for 15 days before continuing the screening process. they will be instructed that they should speak with their family doctor before stopping any prescribed medications. positive urine test for opioids: as regular use of opioid medications is an exclusion criterion, we will do a quality control check with the first 16 participants to test for the presence of opioids in their urine. any participants with a positive test, will be excluded from the study, and such finding will be discussed at the trial steering committee or dsmb for potential trial modification.

pregnant, planning to become pregnant, or breastfeeding opioid medications: any use within last 15 days, as reported by the patient during the trial a positive urine test for opioids (only for the first 16 participants) history of alcohol, opioid or other substance misuse participation in another interventional clinical trial in the last 30 days or planned during the trial period confirmed me/cfs or fm existing prior to sars-cov-2 infection allergy to naltrexone or medication components acute hepatitis, liver failure, or severe kidney failure. current or recent use of naltrexone in the last 30 days the participant is not an ideal candidate for the study, in the opinion of the investigator, for any other reason (ie. personal or logistic, medication, condition, etc.) that could impact the participant's safety or the results of the study. opioid washout period: potential participants who are currently taking opioid medications who wish to enrol the study will be instructed they can stop taking opioid medications for 15 days before continuing the screening process. they will be instructed that they should speak with their family doctor before stopping any prescribed medications. positive urine test for opioids: as regular use of opioid medications is an exclusion criterion, we will do a quality control check with the first 16 participants to test for the presence of opioids in their urine. any participants with a positive test, will be excluded from the study, and such finding will be discussed at the trial steering committee or dsmb for potential trial modification.

pregnant, planning to become pregnant, or breastfeeding opioid medications: any use within last 15 days, as reported by the patient during the trial a positive urine test for opioids (only for the first 16 participants) history of alcohol, opioid or other substance misuse participation in another interventional clinical trial in the last 30 days or planned during the trial period confirmed me/cfs or fm existing prior to sars-cov-2 infection allergy to naltrexone or medication components acute hepatitis, liver failure, or severe kidney failure. current or recent use of naltrexone in the last 30 days the participant is not an ideal candidate for the study, in the opinion of the investigator, for any other reason (ie. personal or logistic, medication, condition, etc.) that could impact the participant's safety or the results of the study. opioid washout period: potential participants who are currently taking opioid medications who wish to enrol the study will be instructed they can stop taking opioid medications for 15 days before continuing the screening process. they will be instructed that they should speak with their family doctor before stopping any prescribed medications. positive urine test for opioids: as regular use of opioid medications is an exclusion criterion, we will do a quality control check with the first 16 participants to test for the presence of opioids in their urine. any participants with a positive test, will be excluded from the study, and such finding will be discussed at the trial steering committee or dsmb for potential trial modification.

pregnant, planning to become pregnant, or breastfeeding any use of opioid medications: within last 15 days, as reported by the patient (or recorded in clinical system used by pcrc clinician) during the trial a positive urine test for opioids (only for the first 16 participants; see below) history of alcohol, opioid or other substance misuse participation in another interventional clinical trial in the last 30 days or planned during the trial period confirmed me/cfs or fm existing prior to sars-cov-2 infection allergy to naltrexone or medication components acute hepatitis or liver failure current or recent use of naltrexone in the last 30 days

pregnant, planning to become pregnant, or breastfeeding any use of opioid medications: within last 15 days, as reported by the patient (or recorded in clinical system used by pcrc clinician) during the trial a positive urine test for opioids (only for the first 16 participants; see below) history of alcohol, opioid or other substance misuse participation in another interventional clinical trial in the last 30 days or planned during the trial period confirmed me/cfs or fm existing prior to sars-cov-2 infection allergy to naltrexone or medication components acute hepatitis or liver failure current or recent use of naltrexone in the last 30 days