Protocol violations in Colombian ivermectin study compromise results

Protocol violations in Colombian ivermectin study compromise results

Interview and article by Christine Clark

Dr David Scheim explains how multiple protocol violations and widespread use of over-the-counter ivermectin could have compromised the results of a recent controlled trial of ivermectin for covid-19 in Colombia.

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The results of a recent randomised, placebo-controlled trial of ivermectin for covid-19 appeared to show that ivermectin was no better than placebo but closer examination reveals a number of problems that call this conclusion into question.  

were no deaths in the ivermectin group and one in the control group, however,
the study population was young (mean age 37 years) and “they were looking at
very nebulous parameters”, notes Dr Scheim.  

problem that is immediately obvious relates to the matter of blinding and
matching of the placebo. “This is supposed to be a double blind study. The first
64 patients – they gave them sugar water. If you’ve tasted ivermectin it’s
bitter; it doesn’t taste bad but it has a real distinctive taste”, explains Dr
Scheim.  Later on the manufacturer of the
ivermectin solution used for the trial provided a reformulated placebo ‘with
similar organoleptic properties’.  “But
they don’t say what it was – no word about its composition, nobody tasted it,
nobody tested it – so it’s not double-blind” comments Dr Scheim.  

three months into the study the lead pharmacist “observed that a labelling
error had occurred between September 29 and October 15, 2020 resulting in all
patients receiving ivermectin and none receiving placebo during this time
frame” 1  “They switched,
mislabelled 38 doses – 38 patients who were supposed to get placebo got
ivermectin so they had to go to contortions to compensate for that”, says Dr

even more serious problem was the widespread availability of ivermectin and use
of over-the-counter by the Colombian population at the time of the study. “Look
at Google searches – they spike. Look at over the counter sales in Cali during
the whole study period – they’re enormous – 1.6 doses of ivermectin for every
case of covid”, says Dr Scheim. The study was designed to monitor patients for
adverse effects characteristic of ivermectin. “They are exactly the same to
0.1.or 0.2% in the ivermectin and the control group…….. basically, it looks
like all the controls were taking ivermectin”, he says. He suspects that many
of the study participants, realising that they had placebo, simply purchased

study totally violated every norm of good procedure so this study is only
useful for the ivermectin group. The conclusion that they put out is totally
unsupported”, concludes Dr Sheim .

Fingerprints of ivermectin

most common adverse effects were headache, dizziness, diarrhoea, nausea and
visual disturbances. Dr Scheim comments, 

“This was quite a high dose of ivermectin – this one of the largest doses used in any clinical study – 7.5 times the normal dose. ………..So they were not serious side effects but they were very characteristic of high-dose ivermectin use and they’re not characteristic of covid. A couple of these adverse effects – the incidence for covid was way less than the incidence for ivermectin. So, you’re getting the identical fingerprints in the ivermectin group and the control group.


  1. Protocol violations in López-Medina et al.: 38 switched ivermectin (IVM) and placebo doses, failure of blinding, widespread IVM sales OTC in Cali, and nearly identical AEs for the IVM and control groups. Scheim DE, Hibberd JA, Chamie-Quintero JJ.

Read and watch the full series on our website or on YouTube.

David E. Scheim received a doctorate in Mathematics
from MIT followed by a post-doctoral
fellowship in mathematical biology. He is an independent medical researcher and