How weight-loss drugs blew out the US trade deficit

The frantic airlift of those ingredients—more than double what was imported from Ireland for all of last year—reflects the collision of two powerful forces: tariff-driven stockpiling and weight-loss drug demand.

The peptide and protein-based hormones feed into a category of drugs that include wildly popular GLP-1 treatments and newer types of insulin known as analogues. Taken together the shipments weighed just 23,400 pounds, according to U.S. trade data, equivalent to the weight of less than four Tesla Cybertrucks.

Fit into temperature-controlled air cargo containers, the pharmaceutical ingredients have had a huge impact on the U.S. trade imbalance. The shipments have vaulted Ireland, a country of only 5.4 million people, into the second-largest goods-trade imbalance with the U.S., trailing only China. They accounted for roughly half of the $71 billion in goods the U.S. imported from the country in the first four months of the year.

Nearly 100% of the imports had a final destination of Indiana, according to U.S. customs records. Eli Lilly, the drug giant behind weight loss and diabetes drugs Zepbound and Mounjaro, is headquartered in Indianapolis.

A Lilly spokeswoman declined to comment.

President Trump’s off-and-on trade war has rewritten global trading patterns this year and—temporarily, at least—widened some of the imbalances he is seeking to eliminate.

Companies have scrambled to get shipments to the U.S. ahead of tariff deadlines, with a first round of front-loading ahead of the April 2 announcement, and smaller pushes after the White House paused some of its tariffs.

Ireland is at the epicenter of the global rush. It is a major hub for U.S. drug giants, who have been expanding operations there in part because of Ireland’s favorable tax policies. Some of the bestselling drugs in the world, such as AbbVie’s anti-wrinkle treatment Botox, and U.S. drugmaker Merck’s cancer treatment Keytruda, are made in the country.

“It’s common sense. It’s uncertain at the moment, so you’re building a bit of security by stockpiling," said Matt Moran, a consultant and former director of industry group BioPharmaChem Ireland. “There’s such huge demand for those products at the moment."

The trade imbalance has put Ireland into an uncomfortable position, landing it earlier this month on the U.S. Treasury Department’s monitoring list for currency manipulation, which the government uses to send a warning shot to countries it thinks use unfair trade practices.

Ireland’s central bank said in a report Thursday that new factories making weight-loss drug ingredients helped drive the country’s exports. Ireland’s first-quarter economic growth expanded by nearly 10% in the first quarter thanks to the export surge.

The attention is “definitely not welcome," said Dan O’Brien, chief economist of the Institute of International and European Affairs, a Dublin think tank. “A very big part of the U.S.-EU deficit is accounted for by Ireland alone. Trump doesn’t like deficits."

The White House wants American drug companies to bring production home and in April ordered a so-called Section 232 investigation that could result in tariffs on both imported drugs and ingredients like hormones.

Trump said this week that such tariffs could come “very soon."

Lilly is a force in the market for weight-loss drugs, with sales of its GLP-1 medicines Mounjaro and Zepbound expected to nearly double this year to about $30 billion, according to Bank of America analysts.

Maintaining supply of weight-loss drugs has been a challenge for both Lilly and rival Novo Nordisk, the Danish maker of Ozempic and Wegovy. The companies were initially unable to keep up with demand for the drugs. Lilly resolved the shortages faster, helping it to take market share from Novo.

Lilly is now preparing for the potential launch of a weight-loss pill, orforglipron, which it plans to submit for U.S. approval later this year. Lilly said it began producing weight-loss and diabetes medicines at its Irish factory in Kinsale in 2023. Novo doesn’t produce weight-loss drugs in Ireland, according to a spokeswoman.

Peptide and protein-based hormones help to regulate processes such as appetite and metabolism. The category includes hormones that mimic a naturally occurring gut hormone called glucagon-like peptide-1, or GLP-1, but can also be used in some fertility and osteoporosis treatments.

Shipping and logistics companies say they have noticed increased demand for pharma shipments, which often travel by air instead of on cheaper ocean freighters because they are so light and valuable.

Pharma shipments more than doubled from Ireland to the U.S. in March and April, according to data firm WorldACD. Kuehne + Nagel, a Swiss logistics company with operations in the country, said its teams did overtime to accommodate the increase in booking requests and the customs paperwork.

“We didn’t see the same increase from Ireland to the rest of the world. That was not a global trend," said Nico Sacco, the company’s senior vice president of healthcare strategy.

Imports of vaccines and various other drugs including cancer treatments also increased this year from Ireland, according to trade data.

Merck produces cancer treatment Keytruda, the world’s bestselling drug, in Ireland, among other places. Merck Chief Executive Rob Davis in April said the company has enough supply to mitigate any impact this year from tariffs and is working on navigating the long-term fallout of tariffs.

Merck recently began construction on its first U.S. plant to make Keytruda. Lilly said earlier this year it plans to invest $27 billion in expanding U.S. production.

The hormones are often freeze dried and shipped as powders. Obesity-related drugs can fly in the cargo sections of passenger planes, or on cargo flights reserved for pharma products, said Anand Kulkarni, head of global markets at Lufthansa Cargo. Lufthansa saw demand for U.S.-bound pharma shipments from locations such as India, Switzerland and Belgium. Volumes began to dip in April as warehouses in the U.S. reached capacity, he said.

To increase shipments, drug companies likely tapped existing stocks and diverted production destined for the rest of the world to the U.S. market instead, industry executives said.

“You can’t just switch on capacity. You don’t go out and buy machines and start them up," said Moran, the consultant. “They have to be built, commissioned, validated, and approved by the regulator."

Write to Chelsey Dulaney at chelsey.dulaney@wsj.com and Jared S. Hopkins at jared.hopkins@wsj.com