You take your medication exactly as your doctor prescribed it. You filled it at a licensed pharmacy. Nothing about that is illegal. And you can still be arrested, charged, and prosecuted for DUI or DWI in Maryland because of it.
That surprises most people — including some who assume a prescription is an automatic shield. It isn't. Here's what Maryland law actually says, how police and prosecutors try to prove these cases, where those cases are often weaker than they look, and what one recent case shows about how they can fall apart before a jury ever hears them.
The Law: Maryland Transportation §21-902(c)
Under Maryland Transportation Article §21-902, it's a crime to drive while under the influence of alcohol, while impaired by alcohol, while impaired by a drug or combination of drugs, or while impaired by a controlled dangerous substance. Subsection (c) is the one that covers medication: it does not carve out an exception for drugs a doctor prescribed. The question the statute asks is whether you were impaired while driving — not whether the drug in your system was obtained legally.
Alprazolam, sold under the brand name Xanax, is a Schedule IV controlled substance. A valid prescription makes possessing it lawful. It does not make driving while impaired by it lawful. (For the practice area overview, see our DUI & DWI defense page.)
Why "I Have a Prescription" Isn't a Defense by Itself
Think of it the way Maryland treats alcohol: having a valid ID to legally buy a drink doesn't matter if you drive drunk afterward. The legality of how you obtained the substance and whether you were impaired while driving are two separate questions, and Maryland's DUI law is built around the second one.
A prescription does matter — just not as an automatic defense. It can support arguments about dosage, tolerance, timing between the dose and the stop, and whether what an officer observed had an explanation other than impairment. It's a piece of the defense, not a shortcut past the charge.
A related question worth knowing the answer to before you're ever pulled over: your rights at a Maryland traffic stop apply the same way whether the officer suspects alcohol or medication.
How These Cases Get Built: DRE Evaluations and Blood Testing
When an officer suspects impairment but a breath test doesn't explain what they're seeing — normal or low alcohol reading, but signs consistent with impairment — Maryland officers are trained to call for a Drug Recognition Expert, or DRE. A DRE is a specially trained officer under the national Drug Evaluation and Classification Program, which NHTSA oversees.
The DRE evaluation is a structured, multi-step protocol:
- Breath-alcohol check
- Interview with the arresting officer
- Preliminary exam & pulse check
- Eye exams (nystagmus, convergence)
- Divided-attention psychophysical tests
- Vital-sign measurements
- Dark-room pupil exam
- Muscle tone & injection-site check
That's followed by an interrogation and the officer's opinion on drug category, which typically leads to a request for a blood or, less often, urine sample, sent to a lab to test for specific drugs or drug classes.
What This Means for a Prescription-Drug Case
Every one of those steps is a potential point of challenge: was the protocol followed correctly, were the officer's observations documented at the time or reconstructed later, was the timeline between the stop and the blood draw long enough to raise real questions, and was the lab's chain of custody intact. A DRE evaluation is trained and structured — but it is still built on one officer's subjective observations.
What a Positive Blood Test Actually Proves
This is where prescription-drug DUI cases often look stronger to a prosecutor on paper than they turn out to be in practice. A blood test confirming the drug's presence tells you it was in your system. It does not, by itself, tell you when you took it, how much, or whether you were impaired at the specific moment you were driving.
Many prescription medications and their metabolites remain detectable in blood for hours or, depending on the drug and the person, longer — well after any impairing effect has worn off. That gap between "detected" and "impaired at the time of driving" is exactly where the State's theory of the case can run into trouble, and exactly where a defense attorney looks first.
The FDA's own consumer guidance acknowledges how individualized medication effects on driving can be — see FDA: Some Medicines and Driving Don't Mix. That variability is part of what a defense has to work with, and part of what a prosecutor has to prove around.
Medical Conditions That Can Look Like Impairment
A DRE evaluation is looking for specific physical signs — certain eye movements, muscle tone, reaction times, pupil behavior. Several of those signs can also show up for reasons that have nothing to do with drug impairment: fatigue and sleep deprivation, anxiety in the moment of being pulled over and evaluated roadside, an unrelated medical condition, blood sugar fluctuations, or a pre-existing neurological or vision condition that affects eye tracking.
None of that means an officer acted in bad faith. It means the evaluation is an interpretation, not a diagnosis, and a competent defense examines whether there's a non-impairment explanation for what was observed — supported, where appropriate, by the driver's own medical history and records.
Case Study: A Case That Never Reached a Jury
In a Baltimore County case our firm handled in 2026, the driver held a valid, active prescription for alprazolam, filled through a licensed pharmacy and taken as directed. Following a traffic stop, the officer requested a DRE evaluation and a blood draw. The blood test came back positive for the prescribed medication.
Rather than accept the State's theory of impairment at face value, the defense examined the DRE evaluation's methodology, the timeline between the stop and the blood draw, and medical explanations for several of the officer's observations.
After the defense raised these evidentiary weaknesses and the resulting reasonable doubt with the prosecution, the State dismissed the case before it reached a jury trial. No conviction resulted.
Details of this case have been generalized to protect client confidentiality, and no identifying facts are included here. Case results depend entirely on the specific facts, evidence, and jurisdiction involved in each matter, and a past result does not predict or guarantee an outcome in any other case.
Wondering how this applies to your own charge? Free, confidential consultations are available around the clock — there's no cost to find out where your case actually stands.
Frequently Asked Questions
Can I get a Maryland DUI for taking prescription medication?
Yes. Maryland Transportation Article §21-902(c) makes it a crime to drive while impaired by a drug, and that includes medication you were legally prescribed and took exactly as directed. A valid prescription does not automatically prevent a DUI or DWI charge — it does not stop an arrest or a charge, but it can become an important part of building a defense. The State still has to prove you were actually impaired while driving.
Does a positive drug blood test prove DUI?
Not by itself. Unlike alcohol's .08 BAC legal limit, Maryland has no equivalent numeric threshold for most prescription drugs. A blood test can show a medication was in your system, but presence isn't the same as impairment at the moment you were driving — many drugs remain detectable well after any effect has worn off. Prosecutors typically combine the blood test with an officer's observations and a DRE evaluation to try to prove impairment, and each part of that can be challenged.
Can I drive after taking Xanax?
That's a medical question first — talk to your prescribing doctor about how the medication affects you specifically, and don't drive if you feel drowsy, dizzy, or slowed down. Legally, Maryland can still charge you with DUI or DWI if an officer believes the medication impaired your driving, even with a valid, current prescription and even if you took it exactly as directed.
What is a DRE?
A DRE, or Drug Recognition Expert, is a police officer trained under the national Drug Evaluation and Classification Program to evaluate drivers for signs of drug impairment when a breath test doesn't explain what the officer is seeing. The evaluation is a multi-step protocol of physical, eye, and psychophysical tests that typically leads to a request for a blood or urine sample. It's protocol-based, but it still rests on one officer's observations — and it can be challenged in court like any other evidence.
Mandeep S. Chhabra
Mandeep is a Maryland trial attorney whose practice centers on criminal defense and DUI/DWI defense across Anne Arundel County and Maryland, including cases involving prescription and controlled-substance impairment charges. He has been recognized by Super Lawyers, Avvo and Martindale-Hubbell, and is a member of the Million Dollar Advocates Forum.
Talk to a Maryland DUI Defense Attorney
If you've been charged with DUI or DWI after taking medication you were legally prescribed, the charge is not the end of the story — but it does need a defense built around the specific evidence in your case: the DRE evaluation, the blood test, the timeline, and your medical history.