Washington (CNN) The White House medical unit frequently functioned as a "grab and go" clinic where mid-level staffers to the most senior officials could obtain prescription drugs without being examined by a doctor , casually pick up the powerful sleeping aid Ambien even for their children, and get drugs that were not prescribed to the person actually taking the medication.

These examples, described to CNN by five of the medical unit's former and current employees and which appear to represent the more problematic practices there, were endorsed by Rear Adm. Ronny Jackson, a doctor.

The allegations shine light on a little-known office on White House grounds skirting some of the most basic medical protocols for years, including under former President Barack Obama. The medical unit serves some White House staffers who work around the clock on high-stakes issues and are unable to easily access their own personal physicians for ailments.

Four former and current White House medical unit employees -- all of whom requested anonymity to discuss behavior they witnessed and were aware of during their tenures -- said prescription medication was handed out readily. In fact, sometimes even the most basic medical consultation was unnecessary.

'Parting gift'

One person who worked at the medical unit under both the Obama and Trump administrations said there was such a "loose control of the controlled medications" that one high-profile Obama administration official who was leaving the White House went to the medical unit for Provigil. The drug promotes alertness and helps individuals stay awake.

It was treated as a "parting gift," the person said, and the outgoing administration official was given around 20 Provigil pills. It is not clear whether this official was ever seen by a White House doctor.

Another of the sources said they witnessed similar requests for pills from outgoing White House staffers. They also recalled being present when one Obama White House staffer came into the outpatient clinic and demanded: "I need to pick up a Z-Pak for myself and my wife."

Z-Pak is the common name for Zithromax, an antibiotic that treats infections. The doctor at the medical unit rejected the request, insisting that the staffer first receive an examination. The doctor was particularly concerned about serious cardiac issues that can result from taking Z-Pak. The staffer grew frustrated, this person recalled, and responded: "Dr. Jackson said I can just pick it up and I don't have to be seen."

Moments later, another colleague walked past the doctor, grabbed the Z-Paks and handed them to the White House staffer.

"You need to just give people these meds when they ask for it," this colleague said -- a message that multiple former medical unit employees said was in line with Jackson's overarching philosophy.

"We would just hand them out. They'd come in and say, 'Hey, can I have an Ambien?' And we would just hand them out. Without having to sign a thing," another person who has recently worked for Jackson told CNN. "We all had a huge problem with it."

Not only was it unnecessary to be examined by a doctor before being handed prescription medication, sometimes, prescriptions were written out for a different person than the intended recipient, according to three former employees with knowledge of the practice.

"People in the unit can pick it up and hand it out to staffers," one person said. "Jackson himself is directing people to do that."

Two people mused that sometimes this was done to protect the identity of a high-profile administration official who needed certain medications.

'Out to get him'

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Some former Obama administration officials are defending Jackson, saying they were only given sleeping aids after being asked routine medical questions. He would ask staffers how long they wanted to sleep and whether they had to get any work done on the flight, before offering drugs ranging from Ambien to non-prescription drugs like melatonin.

"The people who are calling him 'the Candyman' are out to get him," one of the officials said. "White House staffers were expected to make transatlantic flights sleeping on the floor. It wasn't just him."

All interviewees for this story were directly contacted by CNN as accusations about Jackson's management of the clinic have come to light. They agreed to anonymously share what they said were their deep concerns about some of the practices at the unit, which they felt Jackson was responsible in large part for.

Jackson did not respond to a request for comment from CNN for this story. In withdrawing his nomination Thursday morning, Jackson said the range of allegations made against him were "completely false and fabricated."

"If they had any merit, I would not have been selected, promoted and entrusted to serve in such a sensitive and important role as physician to three presidents over the past 12 years," he said. "In my role as a doctor, I have tirelessly worked to provide excellent care for all my patients. In doing so, I have always adhered to the highest ethical standards."

The White House did not respond to a CNN request for comment. A spokesperson for former President Barack Obama also declined to comment.

The practice of casually handing out medication like Ambien and Provigil was not limited to the confines of the White House compound. Several former medical unit staffers said the drugs were freely dispensed on Air Force One.

The distribution of Ambien and Provigil on flights -- including to journalists -- has long been a widespread and accepted practice throughout the US government, including on White House, Defense Department and State Department trips.

Jackson told reporters in a January news conference that Trump himself takes Ambien "on occasion" on overseas travel.

"When we travel from one time zone to another time zone on the other side of the planet, I recommend that everyone on the plane take a sleep aid at certain times so that we can try our best to get on the schedule of our destination," Jackson said.

Prescriptions and monitoring

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Multiple health experts stressed the importance of properly screening for drug interactions, documenting what is prescribed and monitoring for habit formation and complications when physicians prescribe medications like Ambien or Provigil.

"Giving out Ambien or Provigil sleep aids 'like candy' as alleged is still dangerous and irresponsible because these drugs have notorious side effects," said Art Caplan, director of the division of medical ethics at the New York University School of Medicine. "You really don't want to be cavalier about it. These drugs are prescription for a reason -- not the same as an over-the-counter drug."

Dr. Anna Lembke, an associate professor at Stanford University and chief of their addiction medicine clinic, told CNN: "I would never prescribe a drug like that to somebody outside of clinical care. Even within clinical care, I'm very careful about how I use that class of medications."

Those who have worked directly under Jackson insist that Jackson's practices made them uncomfortable. His propensity for doling out medication sent staffers at the medical unit into a frenzy more than once, with multiple people describing a "scrambling" to account for missing medication. Keeping close tabs on how many drugs are dispensed was a practice that simply did not exist at the White House medical unit, they said.

"There was none of that here. It freaked a lot of us here," said the person who has recently worked for Jackson.

Another concerning revelation: White House staffers could easily pick up prescription medication for their children who were accompanying them on official trips. One person described it as "standard practice" for parents to pick up Ambien for their children, while another said they heard about the practice of giving parents Ambien and Provigil for their children from multiple physicians and nurses.

"Some of the stuff they would do for civilian staff members would get really excessive sometimes," one person said. There was a culture of "bending over backwards," they added, "to treat these people."