According to the GroundUp website
South Africa desperately in need of sporting heroes, Impey was a
consistent performer in an unforgiving sport where a few seconds divide
those bathed in glory and those whose names history will not record.
Impey’s legacy, as the first African to wear the famed yellow jersey
in last year’s Tour de France, will be imprinted in history, bringing
glory to himself and his country.
Sadly his opportunity to improve on that feat, or at least repeat it
in this year’s Tour was lost because of his adverse analytical finding,
or what in common parlance is called a ‘positive test’.
Impey tested positive for probenecid, a substance on the Prohibited
List in sport, just before this year’s Tour de France where he was to
ride for team Orica Greenedge.
Probenecid is not performance enhancing, but is prohibited in sport
because it is considered a masking agent – where it could potentially
mask the presence of other performance enhancing substances such as
anabolic steroids or erythropoietin.
While probenecid has been described as a diuretic, it actually is a
‘uricosuric’ drug that increases the urinary excretion of uric acid,
which causes gout. But probenecid’s masking properties are assumed
because of another property that it possesses: it acts to reduce the
renal excretion of some drugs by competing for receptors in the kidney.
So less of the active drug would be excreted in the kidney thereby
increasing its concentration in the plasma. This would have dual
benefits for those using certain performance enhancing drugs: it would
increase the plasma concentration of the drug, enhancing its effects,
and at the same time reduce its excretion in the urine thereby avoiding
detection in urine base doping control tests.
In the clinical context, probenecid can increase the blood
concentration of some antibiotics, antivirals and non-steroidal
anti-inflammatory drugs in order to reduce the required dosage of such
drugs. This proved particularly useful during World War II when there
was a dire shortage of penicillin, which was rapidly excreted via the
kidneys thereby reducing its active life in the plasma. In fact so dire
was the need to save the lives of injured soldiers that the urine of
those using penicillin was collected to isolate the drug and reuse it.
Probenecid proved critical in prolonging the effect of penicillin by
reducing renal excretion.
Probenecid is rarely used today because of the abundance of
synthetically produced penicillin and the availability of superior drugs
to treat gout.
So the case against Impey was predicated on the belief that he had used the drug to mask a prohibited substance.
The procedure in the case of a positive test is that Impey would be
given the right to have his B sample tested - which is split from the
‘A’ sample at collection. Should this confirm the positive test then
Impey either accepts the charge and sanction attendant to committing an
Anti-Doping Rule Violation or appears before an independent tribunal to
plead his defence. He would have the right to full legal and expert
representation, which is the path he chose.
Impey’s defence was simple – that he was the victim of contamination,
which is not an unusual defence. In fact it is the predominant defence
now used by athletes who test positive, in order to invoke the escape
clause provided in the World Anti-Doping Code which is ‘no fault’ or ‘no
significant fault’ thereby avoiding sanction or receiving a reduced
sanction respectively. Essentially this means that the athlete tested
positive through no fault of their own.
Tour de France winner, Alberto Contador claimed in his defence that
the anabolic steroid clenbuterol found in his urine was a contaminant
from meat that he had consumed. His defence was rejected and he was
given a two-year suspension.
Frank Schleck, who came third behind his brother Andy in the 2011
Tour de France, claimed that the diuretic xipamide found in his urine
was due to a contaminated product that he had consumed. His sanction
was reduced by half because of the ‘no-significant fault’ clause and
consequently he only served a one year ban.
Impey’s defence was however novel – he claimed that he tested
positive because the empty gelatin capsule that he purchased from a
pharmacy was contaminated by probenecid, which the pharmacist had
dispensed to a patient two hours prior to Impey. Both products were
dispensed using the same pill-counter, as confirmed in evidence by the
This is highly unusual for a number of reasons. Probenecid is a rarely used drug nowadays; in fact few pharmacies even stock it.
Furthermore, for contamination to occur an uncoated version of the
drug must be used in order to produce residue, or the drug must be cut
or crushed. This is also rare.
What are the chances of Impey being the person who attends the
pharmacy after the patient who was dispensed the rarely used probenecid,
in a rare uncoated form? So the first issue is that all these factors
had to line up against Impey.
Furthermore it seems that the South African Institute for Drug-Free
Sport (SAIDS) had his ‘A’ sample retested – which again is highly
Procedurally confidence in the laboratory results allows an agency to
accept the results of the ‘A’ sample and upon request by the athlete
have the ‘B’ sample tested. ‘A’ samples are only retested should
additional tests be required such as in the case of a testosterone:
epi-testosterone ratio where the sample is sent to a laboratory in
Retesting the ‘A’ sample possibly showed doubt by SAIDS in the
result, the initial laboratory procedure or they wanted to be doubly
sure because of the high profile nature of this case. Regardless, it did
cause a significant delay in this case being brought before a tribunal.
This additional test on the ‘A’ sample is unusual.
This raises another question: probenecid as a masking agent does not
completely block the presence of the active drug in the urine specimen.
With currently available sophisticated tests it is highly unlikely that
residues of the active drug cannot be identified in urine concomitantly
with the masking agent - thereby proving the case of doping rather than
simply relying on evidence of the presence of the masking agent. SAIDS
could have directed the retesting of the ‘A’ sample on attempting to
detect a performance enhancing substance rather than a simple
confirmation of the presence of probenecid.
Most intriguing however is the suggestion being made by some that
SAIDS had accepted Impey’s defence without a challenge before a
tribunal. When a case is brought before a tribunal the prosecution and
defence present their case, including leading evidence and cross
examining all material witnesses, including scientific experts. The
tribunal, consisting of legal and scientific experts, eventually
adjudicates the claims based on a balance of probabilities, as in a
civil case, and makes a determination. In Impey’s case there was none of
this, since SAIDS accepted Impey’s defence without allowing the
tribunal to hear argument. This again is highly unusual.
So why did SAIDS capitulate on this case so easily, or so it seems?
The first is that the defence was so overwhelmingly convincing that the
prosecution felt they had no case. Alternatively, they felt that the
chances of convincing the tribunal seemed remote, and rather than go
through a lengthy and costly process, SAIDS would rather, in a sense,
accept the defence and be done with the case. The counter argument would
be: rather than SAIDS making the decision not to challenge the defence,
why not leave it up to an expert, independent tribunal to make a
reasoned decision after all the evidence is presented before them. This
would seem more objective and fair.
The alternative scenario is a more disconcerting one, with some
evidence to support it – including the retesting of the ‘A’ sample. This
scenario is that there were serious procedural flaws in SAIDS case
which they did not want to expose at a tribunal, particularly if Impey
had world-class experts defending his case. These could be procedural
flaws in the laboratory testing process – which has allowed athletes
such as Gert Thys to be exonerated. Alternately it could be related to
the significant delay in this case costing Impey dearly since he missed
the Tour de France and the Vuelta.
Other procedural flaws could relate to the doping control process,
where the Doping Control Officers may not have strictly complied with
the International Standard for Testing, bringing into doubt the validity
of the results.
Comrades marathon winner Ludwick Mamabolo walked free after, a
tribunal found fourteen irregularities in the doping control process.
If such procedural flaws were exposed in Impey’s case it would be
rather embarrassing to SAIDS, who already have suffered reputational
damage in the case of Mamabolo. This fear would have forced SAIDS into a
cynical calculus – either expose the institute to further reputational
damage or allow an athlete to walk free, without a formal tribunal which
potentially could have publicly exposed such flaws in SAIDS processes.
Of course the athlete could have potentially walked free anyway if
the process was seriously flawed. This conjecture may never be proven
since although the Union Cycliste Internationale and the World
Anti-Doping Agency have a right to appeal, they are unlikely to do so
with a seriously flawed process. Alternately, it may play out in the
courts should Impey wish to sue SAIDS for loss of earnings and damage to
his personal and professional reputation. This would be a great risk
to SAIDS’s future credibility.Shuaib Manjra is a physician with extensive anti-doping experience.