Botswana's Nijel Amos has been banned for three years by the AIU for testing positive for a banned metabolite ©Getty Images

The Athletics Integrity Unit (AIU) has banned Botswana's men's 800 metres Olympic silver medallist Nijel Amos for three years after testing positive for a banned metabolite, with Kenya's Esther Macharia handed a four-year ban following a positive testosterone test.

Morocco's Samir Jouaher has also been provisionally suspended for the alleged presence or use of a prohibited substance.

Amos was provisionally suspended by the AIU in July last year after an out-of-competition test on June 4 returned an adverse analytical finding for metabolites of GW1516.

The three-year ban has been backdated to start on July 12 last year, meaning it runs through to July 11 2025 and Amos will miss the Paris 2024 Olympics.

The AIU said in its ruling Amos asked for tests to be conducted on a sample he said he had consumed before the adverse analytical finding, but no traces were found of GW1516.

Amos admitted an anti-doping rule violation on April 10.

His ban was reduced by the AIU from four years to three because of an "early admission and acceptance of sanction".

Amos' results have been disqualified from June 4 2022 in addition to the ban.

The 29-year-old won Botswana's first Olympic medal with his 800m silver at London 2012, and went on to win gold over the same distance at Glasgow 2014.

He ran a world-leading 1min 42.91sec in Monaco in July 2021 prior to the delayed Tokyo 2020 Games, but missed out on a medal as he placed eighth in the final, which he reached on appeal after a collision with the United States' Isaiah Jewett in the semi-final.

GW1516 was added to the World Anti-Doping Agency's prohibited list in 2009 as a metabolic modulator, a category which covers substances that modify how the body metabolises fat.

Kenyan marathon runner Esther Macharia has been banned for four years after testing positive for testosterone ©Twitter
Kenyan marathon runner Esther Macharia has been banned for four years after testing positive for testosterone ©Twitter

It was originally developed to treat obesity, diabetes and other disorders caused by metabolic problems, but was pulled from clinical trials after being found to cause cancer.

Long distance runner Macharia added to the string of Kenyan athletes provisionally suspended by the AIU in March for the presence of testosterone and its metabolite in an in-competition sample provided at the Singapore Marathon in December last year.

Macharia failed to request a hearing within the AIU's deadline, and failed to return an Admission of Anti-Doping Rule Violations and Acceptance of Consequences Form by April 18.

She has been banned for four years starting from February 21 2023, with all results from December 4 2022 including her Singapore Marathon victory disqualified.

Doping has become rife in Kenya, with more than 60 of the country's athletes on the AIU banned list, and an Anti-Doping Steering Committee has been established aiming to substantially reduce offences.

The Kenyan Government has committed $25 million (£19.9 million/€22.6 million) to the fight against doping in athletics over the next five years.

Moroccan distance runner Jouaher, who ran a personal best 2 hours 8min 42sec to win the Riyadh Marathon in February, has been provisionally suspended from April 6, the AIU also announced today.

This relates to an alleged presence or use of prohibited blood-booster erythropoietin (EPO) or CERA, an EPO variant.