"The wicketkeeper-batsman had inadvertently ingested the prohibited substance, as a contaminant of a weight loss product he was taking, Hydroxycut," the ICC said in a statement.
The 29-year-old Shazad, who has played 58 ODIs and as many T20s for his country, breached article 2.1 of the ICC Anti-Doping Code.
"Mr Shahzad had provided a urine sample as part of the ICC's out-of-competition testing programme in Dubai, UAE, on 17 January 2017," the ICC stated.
His sample was subsequently tested and found to contain clenbuterol. Clenbuterol is classified as a non-Specified Substance by WADA and is prohibited both in-competition and out-of-competition.
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The ICC, however, accepted Shahzad's explanation that he had inadvertently ingested the substance, as a contaminant of a weight loss product he was taking, Hydroxycut.
"Mr Shahzad was able to satisfy the ICC through evidence and submissions prepared on his behalf that he had no intention to enhance his sporting performance through the use of prohibited substances...," the ICC said.
"It further serves as a reminder to all international cricketers of the dangers and risks associated with taking supplements," Allardice said.
"Before thinking about taking a supplement, cricketers should weigh up the risks and dangers of doing so and should fully research the supplement in question so they can make an informed decision," he added.
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