Ask Deandra: Can I Get a DWI in Texas if I’m Only on Prescription Medication?

Prepared June 2026

By Deandra Grant, J.D., M.S. (Pharmaceutical Science), ACS-CHAL Forensic Lawyer-Scientist

The question: Can I get a DWI in Texas if I’m only taking prescription medication?

The short answer: Yes. Texas DWI law does not require alcohol. Under Penal Code §49.01, a person is intoxicated if they have lost the normal use of mental or physical faculties due to the introduction of alcohol, a controlled substance, a drug, a dangerous drug, a combination of any of these, or any other substance. Prescription medications (even ones taken exactly as directed by a licensed doctor) fall squarely within that definition. “It was prescribed” is not a complete defense. A driver taking sleep aids, anxiety medication, opioid pain relievers, certain antihistamines, muscle relaxers, or many other commonly prescribed drugs can be charged with DWI in Texas if the State alleges the medication caused loss of faculties at the time of driving.

Here is the longer answer: what the statute actually covers, which medications drive most prescription DWI prosecutions, why “as prescribed” is not a magic shield, and how a forensic defense addresses these cases.

The Statute Does Not Care That the Drug Was Prescribed

The text of Texas Penal Code §49.01(2)(A) does not distinguish between illegal drugs, lawful drugs, prescribed medications, or over-the-counter products. The statute reaches “any other substance into the body” that causes loss of normal mental or physical faculties. The Texas Court of Criminal Appeals has consistently held that a valid prescription does not exempt a driver from prosecution under §49.04 if the medication caused intoxication.

The legal theory is straightforward, even if the result feels counterintuitive. Texas DWI law is built around the public-safety principle that an impaired driver on the road is a danger regardless of the source of the impairment. A driver impaired by Ambien is not less dangerous than a driver impaired by alcohol and, from the State’s perspective, both should face the same criminal exposure. Whether you agree with that policy or not, it is the law you are working with.

The result is that a sympathetic defendant (a senior citizen taking medications prescribed by a trusted physician for legitimate medical conditions) can find herself charged with the same offense as a drunk driver. The cases are real, they happen across Texas every week, and they are some of the most challenging to defend.

The Medications That Drive Most Prescription DWI Cases

Several categories of prescription medication appear repeatedly in Texas prescription DWI prosecutions. None of these is automatically disqualifying for driving (millions of people take these medications and drive safely every day) but each has documented effects on cognition, reaction time, or motor function that the State will use to argue impairment:

• Sleep aids (zolpidem, eszopiclone, zaleplon). Brand names include Ambien, Lunesta, and Sonata. The FDA has issued specific warnings about morning-after impairment from these drugs and has recommended dose adjustments, particularly for women. “Sleep driving” (driving without conscious memory of the trip) is a documented adverse effect, and prescription DWI cases involving sleep aids are common.
• Benzodiazepines (alprazolam, diazepam, lorazepam, clonazepam). Brand names include Xanax, Valium, Ativan, and Klonopin. Prescribed for anxiety, panic disorder, insomnia, and seizures. Side effects include drowsiness, impaired coordination, slowed reaction time, and cognitive impairment the effects of which can be amplified when combined with even small amounts of alcohol.
• Opioid pain medications (hydrocodone, oxycodone, codeine, tramadol). Brand names include Vicodin, Norco, OxyContin, Percocet, and Ultram. Side effects include sedation, slowed reaction time, and impaired judgment. Combined with alcohol or benzodiazepines, the impairment can be substantial.
• Muscle relaxers (cyclobenzaprine, carisoprodol, methocarbamol). Brand names include Flexeril, Soma, and Robaxin. Frequently prescribed after injuries, back surgery, or for chronic muscle conditions. Sedation and slowed reaction time are well-documented.
• Antihistamines (diphenhydramine, hydroxyzine). Both prescription and over-the-counter. Often used as sleep aids or for anxiety. Significant sedation effects, particularly in older adults whose metabolism processes the drug more slowly.
• Antidepressants and antipsychotics. Some classes of antidepressants and antipsychotics carry warnings about driving and operating heavy machinery, particularly during dose changes.
• ADHD medications. Both stimulant and non-stimulant ADHD medications can affect cognition and behavior in ways that the State may argue produced impairment.
• Texas’s Compassionate Use Program permits low-THC cannabis under specific conditions. Patients enrolled in the program are still subject to DWI prosecution under §49.04 if the medication produced loss of faculties at the time of driving — the prescription does not change the analysis under the loss-of-faculties prong.

This list is illustrative, not exhaustive. The point is that prescription DWI is not an exotic charge. It reaches across the most commonly prescribed drug classes in American medicine. NOTE: Presence in the blood of any of the above listed substances does not prove intoxication. The State must prove that the person charged did not have the normal use of their mental or physical faculties due to that substance.

“As Prescribed” Is Not a Defense But It Matters

Many defendants assume that if they took the medication exactly as prescribed by a licensed physician, they cannot be charged with DWI. That assumption is wrong. The State does not have to prove misuse. The State has to prove loss of faculties and a properly prescribed drug, taken at a properly prescribed dose, can still cause loss of faculties under the right conditions.

That said, “as prescribed” is not legally meaningless. It is part of the defense narrative in several ways:

• Medical context for the jury. Even when no formal involuntary intoxication defense is available, the fact that the medication was prescribed for a legitimate medical condition, taken at a prescribed dose, and consumed without warning of impairment is part of the story the jury hears. It does not eliminate criminal exposure, but it changes the moral framing of the case.
• Mitigation at sentencing. If a case proceeds to a punishment phase, prescription medication context matters. Judges and juries sentence prescription DWI defendants differently than they sentence repeat alcohol offenders.

The realistic message: a prescription does not exempt you from DWI prosecution, but it can shape every part of how the case is defended, negotiated, and ultimately resolved.

Older Adults Face a Specific Risk Profile

This post applies to anyone on prescription medication, but it has particular relevance for older adults. Several factors converge to make seniors over-represented in prescription DWI prosecutions:

• Pharmacokinetic changes with age. Liver and kidney function decline with age, which slows the body’s ability to clear medications. A standard adult dose can produce higher peak concentrations and longer duration of effect in an older patient than the package insert assumes.
• Older adults frequently take multiple prescription medications simultaneously and these are sometimes prescribed by different doctors who do not coordinate. Drug interactions can produce sedation or cognitive effects that none of the individual medications would produce alone.
• Underlying medical conditions. Diabetes, low blood sugar, mini-strokes, dehydration, urinary tract infections, and other medical conditions common in older adults can mimic intoxication on field sobriety tests: unsteady balance, confusion, slurred speech, slow movement.
• Reduced reserve capacity. Younger adults often tolerate medication side effects without obvious behavioral changes. Older adults with less physiological reserve may show effects from the same dose that a 35-year-old would not.

Officers are not trained to distinguish medication side effects, drug interactions, or medical conditions from voluntary alcohol intoxication. They observe behavior and make a charging decision. The forensic and medical context that explains the behavior is often developed only after arrest by the defense.

How the State Builds a Prescription DWI Case

The framework for proving prescription DWI is the same as any drug-based DWI under Texas law. The State has to establish:

• Operation of a motor vehicle in a public place. Driving on a road or highway, in a parking lot open to the public, or in another public location.
• Loss of normal use of mental or physical faculties. Proven through driving behavior, officer observations, statements, field sobriety test performance, and witness testimony.
• Loss of faculties caused by the introduction of a substance. Proven through chemical evidence (typically blood toxicology), the defendant’s own statements about medication use, prescription bottle contents, or pill counts.

Notice what the State does not have to prove: a quantitative threshold of the medication in the blood. Texas has no per-se drug limit. The State has to prove that the substance was present and that it caused loss of faculties (not that it reached a particular concentration). This both helps and hurts defendants. It hurts because there is no “safe” level the defense can point to. It helps because the State has to do the harder work of connecting presence to impairment, and that connection is forensically contestable.

Forensic Defense in a Prescription DWI Case

Defending a prescription DWI case requires a defense lawyer who can work in the medical and pharmacological literature, not just the statute book. The categories of analysis:

• The chemical evidence. Blood toxicology in drug cases is often performed by LC-MS. Method validation, calibration, lower limits of quantitation, matrix effects, and analyst qualifications are all defensible territory.
• The pharmacology. Was the concentration measured consistent with therapeutic dosing or with abuse? Was the drug actively pharmacologically present, or was the analyte a metabolite that proves prior use without proving current effect? Was the concentration in a range associated with documented impairment, or below the threshold at which most patients show observable effects?
• The behavioral evidence. Field sobriety tests are not validated for drug impairment. Officers are trained to look for clues that correlate with alcohol intoxication, not medication side effects. The mismatch between SFST design and drug pharmacology is fertile defense ground.
• The medical context. The defendant’s actual medical conditions, prescription history, treatment plan, and any drug interactions are all part of the case. Subpoenaed medical records and expert medical testimony often surface information that completely reframes the State’s case.
• The DRE evaluation, if performed. Drug Recognition Evaluator examinations are observational, not chemical. The DRE’s twelve-step protocol has documented reliability problems and can be challenged on cross-examination.

Generic DWI defense rarely produces good outcomes in prescription cases. The credentials and the analytical literacy required are different.

What to Do if You Take Prescription Medication and Drive

Practical steps to reduce the risk of prescription DWI exposure:

• Talk to your prescribing doctor about driving. Ask specifically about side effects that affect cognition, reaction time, or coordination. Get the answer documented in your medical record.
• Read the medication guide. Pay particular attention to warnings about driving, operating heavy machinery, and combining the medication with alcohol or other drugs.
• Be cautious during dose changes. New prescriptions and dose increases are when adverse effects are most likely. Avoid driving until you know how a medication affects you.
• Avoid alcohol while taking sedating medications. Even one drink can dramatically amplify sedation, slowed reaction time, and impairment.
• Use rideshare or alternate transportation when in doubt. If a medication makes you feel even slightly off, do not drive. The cost of a ride is dramatically less than the cost of a DWI arrest.
• Keep medication documentation. Carry current prescription information in case you are ever stopped. The documentation does not eliminate exposure, but it can support your defense.

If You Have Been Charged with Prescription DWI

If you have already been charged, several things matter immediately:

• Do not discuss medication use with police or prosecutors without counsel. Statements about what you took, when, and how much can be locked into the record and used to establish the State’s case. Identification information only and nothing further until you have a lawyer.
• Preserve medical records. Your prescribing physician, pharmacy, treating specialists and hospital records all become evidence. Make sure your defense team gets full access.
• Do not stop medication without consulting your doctor. Some medications have serious withdrawal or rebound effects. The fact of being charged is not a reason to stop treatment without medical guidance.
• Hire a DWI lawyer with forensic and pharmacological expertise. Prescription DWI cases live or die on the science. Experience matters, and the right credentials matter.
• Address the ALR deadline. The 15-day administrative license deadline runs from the date of service of the notice of suspension. The criminal medication issues do not change that deadline. However, if you consented to a blood test and your blood analysis does not include a blood alcohol of 0.08 or higher then DPS will not send a notice of suspension. On a consent case drug results alone in a blood test do not trigger a suspension.

The Bottom Line

Texas DWI law reaches prescription medication. “It was prescribed” is not a complete defense, and a valid prescription does not exempt a driver from prosecution if the State alleges the medication caused loss of faculties. Older adults, patients on multiple medications, and patients on common sedating drugs are at particular risk. The defense to a prescription DWI case is not the prescription itself. It is a forensic, pharmacological, and medical analysis of whether the State can actually prove the connection between the drug present and the alleged impairment. That work requires a defense lawyer who understands both the law and the science.

Prescription DWI Defense at Deandra Grant Law

Deandra Grant Law defends DWI and intoxication-offense cases across North and Central Texas including Dallas, Fort Worth, Plano, McKinney, Frisco, Allen, Lewisville, Denton, Rockwall, and Waco. We handle prescription DWI cases with the forensic and pharmacological depth they require: eviewing medical records, analyzing blood toxicology results, consulting with toxicology experts, and challenging the State’s connection between the medication and the alleged impairment. Our team includes an ACS-CHAL Forensic Lawyer-Scientist with a Master of Science in Pharmaceutical Science and a Graduate Certificate in Forensic Toxicology.

If you have been charged with DWI in Texas based on prescription medication, call Deandra Grant Law at (214) 225-7117 or visit texasdwisite.com to schedule a confidential consultation. And remember that the 15-day ALR deadline runs from the date of service of the notice of suspension.

Have a DWI question you want answered in this series? Submit it at texasdwisite.com — you might see it featured in a future Ask Deandra post.