About 40,000 high-strength painkillers were recovered in Craigavon at one of three locations searched by police on Wednesday.
Two men have been arrested.
A police spokeswoman said it was dangerous to take such drugs without a prescription.
Officers were "relieved that such a significant quantity has been removed from circulation", she added.

In his speech to Scottish delegates gathered in Aberdeen, he said "nationalism and populism" might seem like "attractive options".
However, he said the right choice was the Liberal Democrat Party and the influence it could wield in government.
Mr Carmichael said his ambition was to see all 11 Lib Dem Westminster seats in Scotland being retained.
He told the conference: "In a world where nationalism and populism can seem like attractive options - a world where the power of the state and corporate interests can seem to overwhelm the rights and freedoms of the individual - in a world like that liberalism is needed more than ever before and more than ever before our country needs Liberal Democrat influence in government."
Recent polling had suggested that the Liberal Democrats would lose most of its Scottish MPs.
However, echoing similar messages from party leader Nick Clegg and Treasury Minister Danny Alexander, Mr Carmichael said he wanted to prove the doubters wrong about the 7 May election outcome.
He said: "All the clever people tell us - apparently it is over. We are all going to lose. At best I will be the last man standing. Well, let me tell the clever people this. I have campaigned in every general election since 1979."
He added: "In each and every one of these elections the imminent demise of our party has been confidently predicted. Our wipeout has been awaited with relish.
"But somehow - in the face of all the  cleverness - we are still here. We have proved them all wrong before and I promise you this, come May 7th we are going to prove them wrong again.
"We are defending 11 seats here in Scotland, in this election. And we can hold each and every one."
The minister re-capped on the party's time in coalition government and said that Lib Dem influence had helped to:
Mr Carmichael made clear he knew the road so far had been a hard one and there would be more challenges ahead.
But he said he had no intention of cutting more than was needed.
The MP for Orkney and Shetland said: "In this week's budget the Tories softened their plans for PR purposes.
"But they still want to cut further into the fabric of our public finances.
"Further than the economic case requires."
He added: "There must be rich, chauffeur-driven venture capitalists out there who live in gated communities, use private healthcare, have no children, and were born to parents who were either equally rich or who are long since dead, and who would be quids-in under the Tories.
"But for the rest of us on a normal salary or a low salary, or no salary at all, who depend on the NHS, who have children at state schools, or use public transport, or rely on the state pension, or who have dependents, or who just live on the same planet and breathe the same air as most of us do.
"Well, for us, this right-wing, dogmatic, self-centred, ideologically-driven, Ayn Randian dystopia is not a matter of necessity - it is reality of what the Conservatives alone would do in government."
A substantial amount of prescription medication, believed to be stolen, has been recovered by police in County Armagh.
[NEXT_CONCEPT]
Scottish Secretary Alistair Carmichael has said he believes liberalism is needed "more than ever before".