"My doctor immediately told me to try and make myself vomit to see if I could get the medicine to come back up," she said. She was then rushed to Platte Valley Medical Center where she was administered charcoal to absorb the methotrexate.
"For all this to happen now is really overwhelming, to know that I have to come home and wait," said Silva.
It's hard to know how often pharmacies mix up drugs, according to Dr. Alasdair Conn, chief of emergency services at Massachusetts General Hospital.
"The inquiry has not yet been performed but I would not expect a member of the public to question a prescription that has been filled and is labeled 'amoxicillin,' for example," he said. "The patient would have to look at the pills and use a picture dictionary to make sure that the pills are truly amoxicillin-- all tablets and pills have identifiers on them. But I think it is a stretch for anyone to check up in a filled prescription."
Pharmacy mistakes do happen. In 2008, Terry Paul Smith, a 46-year-old roofing contractor, was given the wrong dosage instructions for a painkiller by a Jacksonville, Fla., pharmacist.
He was prescribed to take four 10-milligram tablets of methadone, twice daily. But an inexperienced pharmacist wrote the label to use it "as needed."
He died of an accidental overdose 36 hours later. The pharmacy eventually settled the family's lawsuit.
In 2007, an Atlanta woman was given the powerful antidepressant Trazadone instead of an antibiotic. A bus driver, she was so overcome by dizziness, she nearly ran off the road and had to call for a substitute driver and was hospitalized.
One person was given warfarin, a risky blood thinner, instead of a diabetes medication. Another was treated for Alzheimer's instead of getting the prescribed sleeping pills.
A report in the Atlanta Constitution indicated that about 3 percent of all prescriptions have potentially harmful errors -- the wrong medicine, the wrong dosage or the wrong directions.
In the incident last week in Colorado, Safeway admitted the prescription mistake to ABC and said they would launch a full investigation.
"When the pharmacist became aware of what happened, he worked with the patient and with her physicians to minimize any possible health consequences to the patient and her unborn child," Safeway said in a prepared statement. "We have extended our sincere apologies to the customer, and offered to pay any medical expenses incurred as a result of a prescription error.
"Safeway has pharmacy systems and processes in place to prevent this kind of occurrence," it read. "We have a well-earned reputation for reliably and safely filling prescriptions, and we will continue to work diligently to ensure our procedures and policies are being followed at each of our pharmacies."
But Silva was not happy with their response.
"Sorry's not going to cut it," she said. "I'm going to have to deal with this for a long time. My baby could have deformities. There's a lot that goes with it."
Methotrexate is a "high alert" drug, according to Cohen, and pharmacists and doctors are given a special sheet on it use and should always discuss prescriptions directly with the patient.
"Any time it is prescribed, it does warrant the pharmacist talk directly to the patient, even when the patient doesn't ask to do so," he said. "That's very critical."