Two children who had ingested aripiprazole but not amphetamines tested positive for amphetamine use in urine drug screens (UDSs) performed within 24 hours of their drug use, according to two case reports by Justin Kaplan, Pharm.D., of Hackensack (N.J.) University Medical Center and his colleagues.
In both cases, aripiprazole had been prescribed to the father of the child and had been taken by the child without the knowledge or auspices of a parent. Both of the children were admitted to hospitals where their urine was screened for drugs.
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“To our knowledge this case series is the first to document potential false-positive UDSs after accidental ingestion of aripiprazole,” said the researchers. “In both cases, the presentation of drowsiness, lethargy, and ataxia were more consistent with ingestion of an atypical antipsychotic than with amphetamines.”
In one of the cases, a 2-year-old girl was found holding an open bottle of aripiprazole 15-mg tablets by her parents. The parents’ report of the incident suggested that the child had ingested three such tablets. The child’s urine was screened for amphetamines twice, in the hospital where she was admitted; the first screen, which was performed the morning after the child had been taken to a hospital, revealed an amphetamine concentration of 1,048 ng/mL. The child’s second UDS, which was performed the following day, indicated a 949 ng/mL concentration of amphetamines. Outside of the hospital, laboratory tests were performed on the child’s blood and urine samples from the day following her admittance to the hospital. Both of these additional tests were negative for amphetamines, suggesting that the results of the in-hospital UDSs had been false positives.
The other case involved a 20-month-old girl, whose father found her with pills scattered around her crib. The drugs were part of a 1-week supply of drugs of the father. The medications included alprazolam 2.5 mg, fluvoxamine 2,100 mg, clonazepam 17.5 mg, buspirone 420 mg, and aripiprazole 35 mg. This child’s urine was also screened for drugs twice at the hospital where she was admitted; this child only tested positive for amphetamine in the first assessment, with a 311 ng/mL concentration of amphetamines having been found in that UDS. As with the first case, this child’s urine and blood samples were subjected to off-site laboratory tests, which found no presence of amphetamines.
“There are several limitations to UDS immunoassays. Most important, poor specificity is associated with a risk of false-positive testing. A negative result does not exclude the possibility that the substance is present if it is below the lower threshold of detection. Additionally, there is no way to quantitatively correlate a positive result with the extent of immunoassays. Therefore immunoassays are the first step in a two-step system, in which all positive results must be confirmed by more reliable methods such as [gas chromatography mass spectrometry],” the researchers said.
Read the full study in Pediatrics. doi: 10:1542/peds.2014-3333.