Most people understand that driving drunk is illegal in Tennessee. Fewer understand that driving under the influence of a lawfully prescribed medication is prosecuted under the same DUI statute, with the same penalties, and with the same consequences for your license and your criminal record. Tennessee’s DUI law does not distinguish between illegal drugs and legal prescriptions. If a substance impairs your ability to drive, you can be convicted of DUI for taking it, even if your doctor prescribed it to you yesterday. This post explains how prescription medication DUI works in Tennessee, what the prosecution has to prove, and where the defense openings are.
The Statute: T.C.A. § 55-10-401
Tennessee’s DUI statute is T.C.A. § 55-10-401. It defines three independent ways a person can commit DUI:
- Under the influence of any intoxicant — § 55-10-401(1): driving or being in physical control of a vehicle while under the influence of any intoxicant, marijuana, controlled substance, drug, substance affecting the central nervous system, or any combination that impairs the driver’s ability to safely operate a motor vehicle
- BAC of 0.08% or more — § 55-10-401(2): the per se alcohol standard, which does not apply to drug cases
- Under the influence of any intoxicant while a minor is present — § 55-10-401(3): enhanced DUI with a child passenger under 18
For prescription medication cases, the relevant provision is § 55-10-401(1). The statute uses the phrase “any intoxicant,” which is not limited to alcohol or illegal drugs. It encompasses any substance that impairs the driver’s ability to operate a vehicle safely, including medications that are entirely legal to possess and consume. A valid prescription is not a defense. A doctor’s order is not a defense. The question is whether the substance impaired driving, not whether the substance was lawfully obtained.
This is one of the most counterintuitive aspects of Tennessee DUI law. A person can walk out of a pharmacy with a legally filled prescription, take the medication as directed on the label, and be arrested for DUI an hour later if the medication impairs their driving. There is no safe harbor for following your doctor’s instructions.
No Per Se Limit for Drugs
With alcohol, the prosecution can prove DUI two ways: impairment evidence or a blood alcohol concentration of 0.08% or higher. The 0.08 BAC threshold is a “per se” standard, meaning that a driver is legally intoxicated at that level regardless of whether they appeared impaired.
There is no equivalent per se standard for drugs in Tennessee. There is no nanogram-per-milliliter threshold for any controlled substance or prescription medication that automatically establishes DUI. The prosecution must prove impairment through behavioral evidence, officer observations, and expert testimony. This makes drug DUI cases more difficult to prosecute but also more difficult to predict, because the outcome turns on subjective assessments rather than a numerical cutoff.
Some states have adopted per se drug DUI statutes that set specific thresholds for THC, benzodiazepines, or other common substances. Tennessee has not. In a Tennessee prescription DUI case, the prosecutor has to build a circumstantial case using the totality of the evidence, which typically includes field sobriety testing, body camera footage, blood or urine results, and expert testimony from a drug recognition expert.
Common Prescription Drugs That Lead to DUI Charges
Certain categories of prescription medication are involved in DUI cases far more frequently than others. The drugs most commonly at issue share a common characteristic: they cause drowsiness, impaired coordination, slowed reaction time, or altered perception as a known side effect.
Benzodiazepines
Benzodiazepines such as alprazolam (Xanax), diazepam (Valium), lorazepam (Ativan), and clonazepam (Klonopin) are among the most commonly encountered prescription drugs in DUI cases. They are prescribed for anxiety, panic disorders, insomnia, and seizure disorders. Their therapeutic effects include sedation, muscle relaxation, and reduction of anxiety, all of which can impair driving. The sedative effect is compounded when benzodiazepines are combined with alcohol, even in small amounts.
Opioid Pain Medications
Opioids such as hydrocodone (Vicodin, Norco), oxycodone (OxyContin, Percocet), codeine, and tramadol are prescribed for pain management and produce drowsiness, impaired concentration, and slowed motor function. The label on every opioid prescription warns against operating heavy machinery, which includes driving. Prosecutors point to that label as evidence that the driver knew or should have known the medication would impair their driving ability.
Sleep Medications
Sleep aids such as zolpidem (Ambien), eszopiclone (Lunesta), and zaleplon (Sonata) are designed to induce sleep. Their effects can persist for hours after the person wakes up, a phenomenon known as residual sedation or “hangover effect.” Zolpidem in particular has been associated with a documented pattern of sleep-driving, where the person gets behind the wheel with no conscious awareness of doing so. The FDA issued a black box warning for this class of medication specifically because of driving impairment.
Muscle Relaxants
Cyclobenzaprine (Flexeril), carisoprodol (Soma), methocarbamol (Robaxin), and tizanidine (Zanaflex) are prescribed for musculoskeletal conditions and produce drowsiness and impaired motor coordination. Carisoprodol (Soma) is particularly problematic because it metabolizes into meprobamate, a controlled substance with sedative properties. Soma DUI cases are common in Tennessee.
Antihistamines and Other Sedating Medications
First-generation antihistamines like diphenhydramine (Benadryl) and hydroxyzine (Vistaril) cause significant drowsiness and are frequently found in the blood of DUI defendants. Some antidepressants, antipsychotics, and anticonvulsants also cause sedation at therapeutic doses. The range of prescription drugs that can form the basis of a DUI charge is broader than most people expect.
How Prescription DUI Cases Are Investigated
A prescription medication DUI case typically begins the same way as an alcohol DUI: a traffic stop for a driving pattern that suggests impairment, followed by an officer’s observations at the window. The divergence occurs when the officer suspects drug impairment rather than alcohol impairment.
Field Sobriety Testing
Officers administer the standardized field sobriety tests (SFSTs) in drug cases just as they do in alcohol cases: the Horizontal Gaze Nystagmus (HGN) test, the Walk and Turn test, and the One Leg Stand test. These tests were validated for alcohol impairment, and their applicability to drug impairment is one of the most contested areas in DUI defense. HGN, for example, can be caused by a number of medications that have nothing to do with impairment, including anticonvulsants and certain antidepressants.
Drug Recognition Expert (DRE) Evaluation
If the officer suspects drug impairment, they may request a Drug Recognition Expert (DRE) evaluation. A DRE is a law enforcement officer who has completed a specialized training program designed to identify impairment from seven categories of drugs: central nervous system depressants, CNS stimulants, hallucinogens, dissociative anesthetics, narcotic analgesics, inhalants, and cannabis.
The DRE protocol is a 12-step evaluation that includes pupil size measurement, vital signs assessment, divided-attention tests, and a physical examination. The DRE then renders an opinion about what category of drug is impairing the subject. That opinion is presented at trial as expert testimony.
DRE testimony is one of the most attackable elements of a prescription DUI prosecution. The training program has been criticized for its lack of scientific validation, its subjective scoring criteria, and the high error rate in controlled studies where DREs attempted to identify the specific drug category. A qualified defense attorney can challenge the DRE’s methodology, training records, and the reliability of the protocol itself.
Blood and Urine Testing
Blood draws or urine samples are used to confirm the presence of a drug in the defendant’s system. A positive result for a prescription medication establishes that the drug was present, but it does not by itself prove impairment. Many medications remain detectable in blood or urine for days or weeks after the impairing effects have worn off. The prosecution must still connect the presence of the drug to impairment at the time of driving.
If the blood draw was obtained without a warrant or valid consent, it may be subject to a suppression motion under the Fourth Amendment. Search and seizure protections apply to blood draws just as they apply to vehicle searches.
Defenses to Prescription Medication DUI
Prescription DUI cases are among the most defensible DUI cases because the prosecution has to prove impairment through subjective evidence rather than a numerical threshold.
No Impairment
The central question is whether the medication impaired the defendant’s ability to drive safely. If the defendant’s driving was normal, the field sobriety performance was adequate, and the only evidence of impairment is a positive blood test for a prescribed medication, the case is weak. Many prescription medications are taken daily by millions of people who drive without incident. Tolerance to the sedative effects of a medication develops over time, and a person who has been on a stable dose for months or years may not be impaired at all.
Challenging DRE Testimony
DRE evaluations are vulnerable to cross-examination. The protocol is subjective, the training is inconsistent across agencies, and the scientific validation studies have produced mixed results. A defense attorney can challenge whether the DRE followed the protocol correctly, whether the environmental conditions affected the evaluation, and whether the DRE’s opinion is consistent with the toxicology results.
Medical Conditions
Many of the symptoms that DREs and patrol officers attribute to drug impairment can be caused by medical conditions unrelated to medication use. Nystagmus can be caused by inner ear disorders. Unsteady gait can be caused by neurological conditions, orthopedic injuries, or fatigue. Slow speech and disorientation can be caused by diabetes, stroke, or other medical emergencies. A complete medical history can explain the officer’s observations without any reference to drug impairment.
Suppression of Blood Results
If the blood draw was obtained without a valid warrant or without proper consent, the results may be suppressed. Suppression motions are a powerful tool in any DUI case and can be outcome-determinative when the prosecution’s case depends on toxicology evidence to prove which substance was present.
Pharmacokinetic Defense
Pharmacokinetics is the study of how drugs are absorbed, distributed, metabolized, and eliminated by the body. A defense pharmacokinetic expert can testify about the relationship between the drug concentration in the blood sample and the likely drug concentration at the time of driving. If the blood draw occurred hours after the traffic stop, the drug level measured in the lab may be higher or lower than the level at the time of driving, depending on whether the drug was still being absorbed or had already begun to be eliminated. This retrograde extrapolation analysis, which is commonly used in alcohol cases, is even more complex for prescription drugs because each medication has a unique pharmacokinetic profile.
Implied Consent and Chemical Testing
Tennessee’s implied consent law, T.C.A. § 55-10-406, provides that any person who drives a motor vehicle in Tennessee is deemed to have given consent to a chemical test of their blood, breath, or urine for the purpose of determining the presence of intoxicants. This applies to prescription drug DUI cases just as it applies to alcohol DUI cases.
If a driver refuses to submit to a chemical test, the refusal carries its own consequences. The driver’s license is revoked for one year for a first refusal, regardless of whether the DUI charge itself results in a conviction. The refusal can also be introduced as evidence at trial, where the prosecution will argue that the driver refused because they knew the test would confirm impairment.
In practice, law enforcement officers who suspect drug impairment will typically request a blood draw rather than a breath test, because a breathalyzer does not detect drugs. If the driver refuses the blood draw, the officer may apply for a search warrant authorizing a forced blood draw. Tennessee courts have upheld the constitutionality of warrant-based forced blood draws in DUI cases following the United States Supreme Court’s decision in Missouri v. McNeely, which held that the natural dissipation of alcohol in the bloodstream does not create a per se exigency that justifies a warrantless blood draw.
The timing of the blood draw matters in prescription medication cases. Unlike alcohol, which metabolizes at a relatively predictable rate, prescription drugs have varying half-lives and metabolic pathways. A blood draw taken hours after the traffic stop may show a different drug concentration than what was present at the time of driving. The defense can use pharmacokinetic evidence to argue that the drug level at the time of the blood draw does not represent the level at the time of the alleged impaired driving.
Penalties for DUI in Tennessee
Prescription medication DUI carries the same penalties as any other DUI under T.C.A. § 55-10-403. The penalties escalate with each subsequent offense.
- First offense DUI: 48 hours to 11 months 29 days in jail (mandatory minimum 48 hours or 7 days if BAC was 0.20+), fines of $350 to $1,500, one-year license revocation, possible ignition interlock device, DUI education course
- Second offense DUI: 45 days to 11 months 29 days in jail (mandatory minimum 45 days), fines of $600 to $3,500, two-year license revocation, vehicle seizure, mandatory ignition interlock
- Third offense DUI: 120 days to 11 months 29 days in jail (mandatory minimum 120 days), fines of $1,100 to $10,000, six-year to ten-year license revocation, vehicle seizure, Class A misdemeanor
- Fourth or subsequent DUI: Class E felony, one to six years in prison (mandatory minimum 150 consecutive days), fines of $3,000 to $15,000, permanent license revocation with no restricted license available for the first year
In addition to these criminal penalties, a DUI conviction creates collateral consequences that are particularly significant for people who hold professional licenses. Nurses, pharmacists, commercial drivers, teachers, and attorneys face potential disciplinary action from their licensing boards following a DUI conviction. The professional consequences can be more devastating than the criminal penalties, especially for first offenders who may receive probation on the criminal case but lose their ability to practice their profession.
Insurance consequences are also severe. A DUI conviction results in the requirement to carry SR-22 high-risk insurance for a period of years. The increased premium cost over the SR-22 period routinely exceeds the criminal fines by a substantial margin.
For more information about how Tennessee handles DUI charges, including the differences between per se and impairment DUI, see DUI Per Se vs. Impairment in Tennessee. If your DUI case involved a traffic stop or checkpoint, your rights at DUI checkpoints in Nashville may be relevant to the defense.
Frequently Asked Questions
Can I get a DUI for taking medication my doctor prescribed?
Yes. Tennessee’s DUI statute at T.C.A. § 55-10-401(1) covers driving under the influence of any intoxicant, including lawfully prescribed medications. A valid prescription is not a defense. The question is whether the medication impaired your ability to drive safely, not whether you had a legal right to take it.
Is there a legal drug limit for driving in Tennessee?
No. Unlike the 0.08% BAC threshold for alcohol, Tennessee has no per se nanogram-per-milliliter limit for any drug. The prosecution must prove impairment through behavioral evidence, officer observations, field sobriety test results, and expert testimony. A positive blood test showing the presence of a drug is relevant but does not by itself establish impairment.
What drugs most commonly lead to prescription DUI charges?
The medications most frequently involved in prescription DUI cases are benzodiazepines (Xanax, Valium, Klonopin, Ativan), opioid pain medications (hydrocodone, oxycodone, codeine, tramadol), sleep medications (Ambien, Lunesta), muscle relaxants (Flexeril, Soma), and first-generation antihistamines (Benadryl). All of these medications cause drowsiness, impaired coordination, or slowed reaction time as known side effects.
Can a DRE’s opinion be challenged in court?
Yes, and DRE testimony is one of the most vulnerable parts of a prescription DUI case. The DRE protocol has been criticized for its subjective scoring, inconsistent training standards, and limited scientific validation. A defense attorney can challenge whether the DRE followed the protocol correctly, whether the evaluation conditions were appropriate, and whether the DRE’s drug category opinion is consistent with the toxicology results.
What happens to my prescription if I am convicted of DUI?
A DUI conviction does not affect your prescription. Your doctor may continue to prescribe the medication, and your pharmacy will continue to fill it. The conviction does affect your driving privileges, your criminal record, and your insurance rates. If the judge imposes conditions of probation, those conditions may include restrictions on driving while taking certain medications, but the prescription itself is not revoked or modified by the court.
Talk to a Criminal Defense Lawyer
If you are facing criminal charges in Nashville or anywhere in Middle Tennessee, attorney Nathan Cate can help you understand what you are up against and what your options look like. Nathan has tried 53 jury trials to verdict in Tennessee courts, with 12 outright Not Guilty acquittals. He is a court-qualified criminal defense expert witness who handles every category of criminal case in Davidson County and throughout Middle Tennessee.
Call (615) 664-8083 to schedule a consultation, or visit the office at 222 2nd Avenue North, Suite 220, Nashville, TN 37201.
You can also learn more about Tennessee criminal law on this site, including pages on the difference between felonies and misdemeanors, Tennessee sentencing ranges, and the criminal appeals process.