A combination drug is a preparation of multiple pharmaceuticals or active ingredients in a single dosage form, the most common type of which is the fixed-dose combination drug, a mass-produced and mass-marketed item of standardized and uniform active ingredients and chemical bonds at predetermined, unchanging, exactified doses. A polypill is a pill containing four or more active ingredients^[1][2] frequently needing to be compounded in order to satisfy an individual's specific and individualized treatment needs, per the patient's medical prescription. Compounded preparations most often consist of approved prescriptions or over the counter drugs, but if indicated, may also include nutritional supplements, amino acids, vitamins and minerals, hormones, etc.)^[3]

Fixed-dose combination drugs were initially developed to target a single disease, as with antiretroviral FDCs indicated for treating AIDS and HIV.^[4]

The concept of combination drugs has come to include reducing pill burden for patients, thereby encouraging patient compliance, and generally simplifying treatment plan with one product containing easily accessible (often available over the counter without a prescription requirement), relatively affordable (often generic drugs) ingredients with established therapeutic efficacy and a broad capacity for treating a variety of symptoms and conditions, thus ensuring maximum appeal to a majority of patients amongst a large population with varying needs.

Examples of over the counter, inexpensive combination drugs capable of treating plural symptoms are those containing nonsteroidal anti-inflammatory drugs (abbreviated NSAID), a chemical class including aspirin, ibuprofen, and naproxen, among others). NSAIDs are indicated for treating a range of symptoms, including neck and shoulder pain, back pain, joint or arthritic pain likely stemming from inflammation and swelling, as well as in the relief of tension, cluster, or migraine headaches. Among NSAIDs, aspirin is particularly cardioprotective, with decades of efficacy as an anticoagulant and blood thinner associated with decreased risk of developing cardiovascular disease, heart attack, or stroke.^[5]

A patient at risk for cardiovascular disease and simultaneously experiencing widespread or localized aches and pain, inflammation or swelling of joints, and/or headache may find a fixed-dose combination drug such as Anacin (each tablet contains 400mg aspirin and 32mg caffeine), may be an ideal treatment option for their symptomology. It is noteworthy that caffeine, in its own right, has demonstrated ability to relieve headaches.^[6] Excedrin is marketed specifically for tension headaches, and includes acetaminophen in addition to aspirin and caffeine. Acetaminophen is not an anti-inflammatory and is inconsistent in terms of effectively relieving pain; is has historically been known and used for its antipyretic (fever reducing) properties, although it does appear to possess drug synergy when used alongside an anti-inflammatory/NSAID and caffeine, thus potentiating the analgesic effects of each other. Ultimately, both products are available for sale over the counter at multiple locations at a relatively inexpensive price point able to treat multiple symptoms with two or three appropriate ingredients at proper doses in one dosage form.

The combination drugs listed below are typically available by prescription only, but specific circumstances regarding a given combination's legal accessibility, or any specific regulation pertinent to ingredient quality, quantities, production standards, sourcing, etc. will vary by jurisdictions:

• Adderall: dextroamphetamine sulfate, amphetamine sulfate, dextroamphetamine saccharate, amphetamine aspartate monohydrate; indicated for treating attention deficit hyperactivity disorder and narcolepsy.
• Contrave: bupropion (stimulating antidepressant) combined with naltrexone (an opioid antagonist); indicated for aiding smoking cessation and weight loss.
• Qsymia: phentermine hydrochloride (central nervous system stimulant and anorectic), topiramate (anticonvulsant, appetite suppressant and relieves migraines)indicated for weight management as an anorectic and anti-obesity drug

• Lephotan: ephedrine (sympathomimetic decongestant) combined with ethylmorphine (antitussive, analgesic agent)
• Librax: chlordiazepoxide combined with clidinium bromide is indicated for treating gastrointestinal ulcers
• Paxlovid: granted emergency use authorization by the U.S. Food and Drug Administration for the treatment and management of COVID-19.^[7]
• Coldec, Ceron (pill dosage form), Rondec Syrup (liquid iincture): carbinoxamine 4mg chlorpheniramine maleate (sedating [first generation antihistamine]]) combined with 12.5mg phenylephrine hydrochloride (sympathomimetic); Unavailable in the U.S.^[8]

• Omidria, phenylephrine (mild sympathomimetic and vasoconstrictor) combined with ketorolac; preservation of eye tissue during opthalmalogic surgery

• Talicia: Omeprazole (proton pump inhibitor) combined with amoxicillin (anibiotic) and rifabutin

• Azor: amlodipine besilate combined with olmesartan medoxom (ACE Inhibitor),; second-line treatment of hypertension.
• Conduet, treatment of hypertension with comorbid hypercholesterolemia
• Consensai: amlodipine medoxom combined with celecoxib (COX-2 inhibitor)' indicated for treating hypertension comorbid to hypercholesterolemia and/or osteoarthritis pain.
• Exforge: amlodipine combined with valsartan (Angiotensin II receptor antagonist)
• Zestoric, Prinzide: lisinopril (ACE inhibitor) combined with hydrochlorothiazide (diuretic); treating hypertension
• Lisonorm, Dironorm): lisiniopril combined with amlodipine (calcium channel blocker), hypertension
• Lotrel by Novartis: ratios beginning 5mg amlodipine besilate (calcium channel blocker) combined with 10mg benazepril hydrochloride (ACE inhibitor); consecutive ratios include 5:20 amlodipine:benazpril, 10:20, and 10:40; indicated as a second-line antihypertensive

• Triavil: amitriptyline perphenazine
• Deanxit by Lundbeck: 0.5mg flupenthixol (typical antipsychotic) and 10mg melitracen (tricyclic antidepressant), available in India, indicated for major depressive disorder and dysphoria
• Limbitrol: 12.5mg amitriptyline HCL (sedating TCA, nerve pain relief, 5mg chlordiazepoxide (mild benzodiazepine anxiolytic and muscle relaxant); Limbitrol DS is the double-strength formula: 25mg amitriptyline hydrochloride and 10mg chlordiazepoxide; treating moderate to severe depression, social anxiety, generalized anxiety, and insomnia.
• Auvelity by Axsome Therapeutics: 45mg dextromethorphan hydrobromide and 105mg bupropion hydrochloride; indicated for major depressive disorder.^[9]
• Symbyax: indicated for schizophrenia and Bipolar I and II Disorders
• MDMA/citalopram: an empathogen called "Ecstasy" combined with citalopram (SSRI); currently under development in FDA Phase II clinical trials.^[10]

• Percocet: 5mg oxycodone and 325mg acetaminophen
• Obedron: 5mg hydrocodone bitartate (antitussive) and 400mg guaifenisin (expectorant)
• Vicodin, Norco: 10mg hydrocodone and 325mg acetaminophen
• Percodan: oxycodone (opioid) combined with aspirin (NSAID).
• Butapap: combines butalbital, acetaminophen, caffeine and codeine
• Combunol: 5mg oxycodone and 400mg ibuprofen,
• Azdone: hydrocodone (antitussive) and NSAID (potentiating analgesic)
• Ibudone: opioid and NSAID, potentiating analgesics

• Anervan: Ergotamine, chlorcyclizine, and caffeine, indicated as an anti-migraine medication
• Arthrotec: diclofenac sodium (NSAID) combined with misoprostol (GI Tract Prostaglandin-protectant)
• Obredon: hydrocodone (opioid) and guaifenisin (expectorant), treatment of chronic pain and loosen phlegm.
• Brontex: guaifenesin (expectorant to thin mucus and phlegm, ease chest congestion) and codeine (mild opioid analgesic)
• Butapap: butalbital (barbiturate tranquilizer and muscle relaxant) combined with paracetamol(mild analgesic, also called acetaminophen, caffeine (stimulant, migrain relief) and codeine (mild opioid)
• Cafergot, Migergot: caffeine and ergotamine;treatment of headaches
• Donnatal: phenobarbital, sulfates of hyoscyamine and atropine, and scopolamine hydrobromide (latter two ingredients derive from Atropa bella-donna deadly nightshade-derived indicated for the treatment of acid reflux , GERD
• Excedrin: aspirin , acetaminophen, and caffeine; indicated as analgesics for tension headache and migraine
• Fiorinal: butalbital (barbiturate sedative, muscle relaxer) combined with aspirin (NSAID) and caffeine (anti-migraine, stimulant); treatment of tension headache, cluster headache, migraine
• Fioricet: butalbital (muscle relaxant) combined with acetaminophen and caffeine; treatment of tension, cluster, and migraine headaches
• Saridon: caffeine combined with propyphenazone (long-acting antipyretic) and paracetamol (short-acting antipyretic and mild analgesic); indicated for reducing fever and treating minor aches, and relieving fatigue and lethargy.
• Sybravo: Meloxicam (NSAID) combined with rizatriptan (triptan); antimigraine medication; recently FDA-approved drug in January 2025
• Treximit (sumatriptan/naproxen): sumatriptan (triptan antidepressant) combined with naproxen sodium (NSAID)

Fixed-dose combination drugs for sale over the counter internationally, including medicine indicated for various purposes:

treating motion sickness, nausea, and vomiting, and well as allergy symptoms, including:

• Anacin: 32mg caffeine and 400mg aspirin^[11]
• Dramamine, itself a combination of 8-chlorotheophylline and diphenhydramine, used to treat motion sickness and nausea.
• Emetrol for Nausea: antiemetic taken to relieve nausea and vomiting
• Excedrin: fixed dose of aspirin, acetaminophen, and caffeine; for treating tension and migraine headaches
• Drixoral'): dexbrompheniramine (antihistamine), pseudoephedrine (decongestant), in Canada
• Duexis: NSAID and proton pump inhibitor for acid reflux, indigestion, and general mild pain relief and arthritis pain.^[12]

• Aleve PM (combination naproxen/diphenhydramine), 220mg naproxen, 12.5mg diphenhydramine hydrochloride, analgesic sleep aid
• Advil PM (ibuprofen/diphenhydramine) 400mg ibuprofen, 25mg diphenhydramine hydrochloride
• Tylenol PM: 500mg acetaminophen, 38mg diphenhydramine hydrochloride

The following medications consist of a variety of active ingredients indicated for cough (cough suppressants), congestion (expectorants and nasal decongestant, antihistamines, and/or an antipyretic (fever-reducing agent). In the United States, any of the products listed below containing ephedrine or pseudoephedrine are not prescription drugs, but they are stored behind the pharmacy counter, and requires additional steps to complete purchase of these products per U.S. federal law, the Combat Methamphetamine Epidemic Act of 2005:^[13]

• Allegra-D, a second-generation antihistamine and a sympathomimetic decongestant
• Claritin-D, a second-generation antihistamine and an activating decongestant
• Zyrtec-D, 5mg ceterizine (second-generation antihistamine), sympathomimetic decongestant
• Aleve-D: 220mg naproxen (NSAID) and pseudoephedrine (sympathomimetic)
• Robitussin: cough medicines comprising dextromethorphan, acetaminophen, chlorpheniramine,
• Allerest, Chlor-Rest, Tri-Nefrin (oral pill formulation); Altec Syrup (oral liquid syrup); Vernate (liquid injection) by Tutag Pharmaceuticals: 8mg chlorpheniramine maleate and 50mg PPA per serving.^[14][15][16]: chlorpheniramine (first-generation antihistamine) and phenylpropanolamine (PPA, a sympathomimetic nasal decongestant)
• Coricidin Cold & Cough by Bayer: fixed-dose combination drug containing dextromethorphan hydrobromide (a cough suppressant), 2mg chlorpheniramine maleate (first-generation antihistamine), and 200mg guaifenesin (expectorant); indicated for cough, cold-like and flu-like symptoms, allergic rhinitis, chest congestion; Coricidin HBP contains an additional 325mg acetaminophen.^[17]
• Oxomemazine/guaifenesin combines oxomemazine (sedative antihistamine) and an expectorant, respectively. Never FDA-approved for use in the U.S.
• Sudafed PE): guaifenesin, phenylephrine (expectorant and nasal decongestant).

• Temaril-P: alimemazine and prednisolone; indicated as antitussive and antipruritic in dogs, generic since 2024. The generic alternative to the brand version substitutes alimemazine with trimeprazine, but is otherwise identical in terms of formulation and efficacy.
• Titzeol: combination of tiletamine and zolazepam both major tranquilizers, intended to sedate large animals^[18]

The limitations of combination formulations currently available for treating a widely-inclusive collection of symptoms such as Tourette's is highlighted by there not being a polypill or any combination formula period approved for treating the condition. Medication available, and sometimes used in the context of polypharmacy involves various individual medicines for treating tics and/or generalized anxiety or social anxiety disorder and/or obsessive-compulsive anxieties with use of individual benzodiazepines or SSRIs for the former two conditions, and fluvoxamine or clomipramine first-line treatments for OCD and related disorders, such as hoarding or compulsive decluttering. But, where Attention-Deficit Hyperactivity Disorder, depression, or insomnia become a primary concern to the patient, it is only through polypharmacy (in this case, adding another antidepressant or a "booster, alongside a hypnotic soporific agent, and/or psychostimulants to both treat ADHD and counteract the sleep inertia, grogginess or hangover caused by the other evening medications).

Tourette syndrome is a neurological tic disorder whose only FDA-approved treatment is the neuroleptic pimozide, a drug only used for tics due Tourette's disorder; every other treatment is an off-label use. While Tourette's is typically identified by chronic motor and vocal tics–"semi-voluntary" movements and noises made in response to a "premonitory urge," an internal buildup of compulsive tension that can only be temporarily upon performing/making the motion/sound demanded by compulsion. Tourette's, however, is an all-encompassing umbrella term that includes not just chronic physical and phonic tics, but also presents with such comorbid symptoms as anxiety (often OCD, social anxiety, schizoid personality, avoidant personality disorder, or generalized anxiety), ADHD, insomnia, depression, and traits of high-functioning autism formerly called Asperger syndrome.

• Acutran (amfecloral): dextroamphetamine sulfate and chloral hydrate), discontinued 1973
• Ambar (standard release): unknown doses of methamphetamine hydrochloride and phenobarbital; Ambar Extentab (XR) formulation
• Amvicel: 10mg dextroamphetamine sulfate, 40mg amobarbital, 15mg phenobarbital; Amvicel-X: supplemented with multivitamins (A, B, and C), minerals (calcium, iron, manganese, zinc), and 30mg nicotinamide
• Anox polypill capsule by Winston Biotech: sustained-release 7.5mg methamphetamine hydrochloride, 7.5mg dextroamphetamine sulfate with 20mg phenobarbital, 20mg butabarbital, 20mg secobarbital; Diacelx: extended-release formulation launched 1965^{[citation needed]}
• Anxine: 2.5mg dextroamphetamine sulfate, 35mg cyclobarbital, and 120mg mephenesin (a muscle relaxant)
• Appetrol: 5mg dextroamphetamine, 400mg meprobamate (tranquilizer and anxiolytic)
• BamaDex: 6mg dextroamphetamine, 400mg meprobamate (minor tranquilizer and anxiolytic)
• Biphetamine T-12.5by Fisons:12.5mg racemic amphetamine (1:1 mixture 6.25mg levoamphetamine:6.25mg dextroamphetamine)
• Biphetamine T-2020 by Fisons: 20mg [[racemic [[amphetamine (1:1 mixture 10mg levoamphetamine:10mg dextroamphetamine)
• Desbutal: 5mg methamphetamine hydrochloride and 30mg pentobarbital, discontinued 1973
• Dexamyl: dextroamphetamine and amobarbital, discontinued 1982
• Durophet M: 13mg racemic amphetamine (1:1 6.25mg levoamphetamine:6.5mg dextroamphetamine, 40mg methaqualone hydrochloride
• Esbelcaps: 20mg fenproporex,6mg diazepam, Mexico, Panama, Honduras, Nicaragua, Dominican Republic^[19]
• Euphoramin: 5mg methamphetamine hydrochloride, 300mg meprobamate
• SynaTan-S, later ObaTan-S by Neisler Laboratories: combination of 10mg Tanphetamin (generic trademark for the compound dexamphetamine tannate) combined with 35mg secobarbital to create an FDC marketed as SynaTan-S. Upon being acquired by Mallinckrodt in 1976, SynaTan was rebranded OboTan: formerly SynaTan.^{[20][21][22][23]}
• Phelantin (capsule) by Parke-Davis: 100mg phenytoin (anticonvulsant), 30mg pentobarbital (depressant, antiepileptic), and 2.5mg methamphetamine hydrochloride (mild counteraction of sedation)

• Amphaplex 10:2.5mg methamphetamine saccharate, 2.5mg methamphetamine hydrochloride, and 5mg racemic amphetamine sulfate (2.5mg levoamphetamine sulfate:2.5mg dextroamphetamine;^[24] and Amphaplex 20– 5mg methamphetamine saccharate, 5mg methamphetamine hydrochloride, and 10mg racemic amphetamine sulfate (5mg levoamphetamine sulfate: 5mg dextroamphetamine sulfate)
• Bontril Timed No. 1: 2.5mg dextroamphetamine and 7.5mg butarbartal; Bontril Timed No. 2: 5mg dextroamphetamine, 15mg butabarbital; Bontril No. 3: 10mg dextroamphetamine, 30mg butabarbital; Bontril Timed No. 4: 15mg dextroamphetamine, 60mg butabarbital ^[a][25]
• Delcobese was 4 components of single-entity racemic amphetamine: 1/4 racemic amphetamine (l- and d- isomers) adipate and 1/4 racemic (l- and d- isomers) amphetamine sulfatedextroamphetamine adipate, and dextroamphetamine sulfate.
• Obetrol by Abbott Laboratories was a combination of various mixed salts of methamphetamine and dextroamphetamine salts; discontinued in 1973 following a crackdown by the DEA on combination drugs composed of controlled substances of the DEA and a subsequent crackdown on combination medicines. Obetrol was reformulated as Oby-Rex and replaced the methamphetamine salts with salts from the other half of racemic amphetamine, which is technically a single entity, hence obyRex.hetamine.
• Pondimin ("Fen-Phen") – fenfluramine/phentermine, anti-obesity medication discontinued 1998^[26]

• Amplus Now^[27] by Pfizer-Roerig Inc.^[28]–combined 5mg dextroamphetamine sulfate and 5mg hydroxyzine
• NalerTan and Durabond: 10mg dextroamphetamine tannate, 8mg chlorpheniramine tannate, and 25mg pyrilamine tannate^[29][30]
• Obocell by Irwin, Neisler and Co.: 5mg dextroamphetamine phosphate 25mg methapyrilene phosphate; Obocell-TF was Obocell with added :high-viscosity methylcellulose)^[31]
• Pre-M-T, FDC polypill tablet by Behlen Laboratories: microdose of theobromine syngerstically potentiates racemic amphetamine sulfate–by definition, an equal 1:1 ratio of levoamphetamine to dextroamphetamine– the two depressants are the highly-potent barbiturate sodium pentobarbital, combined with the mildy sedating first-generation antihistamine pyrilamine maleate. Additionally, a microdose of theobromine which a very mild "stimulant" related to caffeine and found in cacao and chocolate. The low dose simply provides drug synergy between the other four compounds.

• Eskatrol by Smith, Kline & French (now GlaxoSmith Kline) – Among the top 200 prescription drugs indicated for weight loss in the U.S. in 1980 dextroamphetamine and prochlorperazine, discontinued 1981

• Reladorm – 100mg cyclobarbital and 10mg diazepam, insomnia treatment (soporific) in Russia, discontinued 2019
• Tuinal– Tuinal combined two barbiturate salts, namely sodium amobarbital and secobarbital, discontinued late 1990s

• Mandrax – methaqualone and diphenhydramine, formerly available in South Africa, now limited to clandestine chemistry

• Artogesic: – dextroamphetamine and mephobarbital with phenacetin and salicylamide
• Apamead – dextroamphetamine sulfate and amobarbital with aspirin and phenacetin
• Dysonil – methamphetamine hydrochloride, pentobarbital sodium, and salicylamide)
• Edrisal–160mg aspirin, 160mg phenacetin, and 2.5mg amphetamine sulfate; Edrisal with Codeine was an identical formulation that included the addition of 16mg codeine
• Daprisal by GlaxoSmith Kline – dextroamphetamine sulfate, 32.5mg amobarbital, and 162.5mg aspirin
• Decobese – 15mg dextroamphetamine and 16mg amobarbital, with 75mg betaine anhydrous and 194mg bile salts
• Direcel: dextroamphetamine, butabarbital, and carboxymethylcellulose; Direcel-T was identical with the inclusion of thyroid hormone
• Duodex – capsule containing 16.25 mg aloin, 15mg amphetamine sulfate, 16.25mg pentobarbital, and thyroid hormone
• Elpanal by Teva Pharmaceuticals: 500mg acetaminophen, 15mg amobarbital, and 2.5mg methamphetamine hydrochloride; Lamital by Teva was merely the sustained-release formulation.
• Mediatric – 0.25mg Premarin (Conjugated Estrogens USP), 2.5mg methyltestosterone, 100mg ascorbic acid, B vitamins, and 1mg methamphetamine hydrochloride
• Nexorin: dextroamphetamine sulfate, amobarbital, methylcellulose, and supplements
• Obolip: dextroamphetamine and phenobarbital, with choline bitartrate, di-methionine, and methylcellulose

Most of the combination drugs which have been discontinued since the twentieth century were simultaneously indicated and utilized for treatment of various conditions, with medical use justified as part of a multifaceted, comprehensive approach to patient health care and medical treatment. Central nervous system stimulants (colloquially called "uppers") were used as appetite suppressants, antidepressants, and wakefulness-promoting agents, and further effects include increased mental alertness and concentration/focus, as well as physical energy and motivation. The addition of a central nervous system depressant mitigated the stimulant's adverse effects without eliminating therapeutic benefits. In most cases, the "upper" component of these combination drugs was a salt, or mixed salts, of racemic amphetamine, dextroamphetamine, or methamphetamine, while the "downer" was typically one or more barbiturates (most commonly amobarbital, phenobarbital, pentobarbital, and/or secobarbital) or similar GABAergic, non-barbiturate tranquilizers or sedatives, frequently meprobamate or methaqualone, respectively, which provided anxiolytic, muscle relaxant, and hypnotic effects. Upper and downer combination drugs were often capable of substituting for Monoamine Oxidase Inhibitors (MAOIs) in patients with treatment-resistant depression where MAOIs are indicated, but where MAOI-related dietary restrictions would impact patient's life.

There are advantages and disadvantages of combination drug therapy, including using fixed-dose combination drugs and/or polypills, as opposed to partaking in polypharmacy and increasing one's pill burden by keeping track of an organized schedule or any FDCD with 2, 3, or 4 active ingredients, relative to the concept of polypharmacy. Overall, giving patients the ability to take control and alleviate symptoms, and potentially treat or cure multiple conditions by consuming all of their medical treatments efficacious treatment options by the ingestion of a single pill, which consistently improves patient medication compliance by reducing their pill burden. The American Association of Orthodontists asserts that fixed-dose combinations "limit clinicians' ability to customize dosing regimens."^[32] AAO states their organizational position is that custom-compounded fixed-dose combination drugs, as well as compounded polypills are superior to mass-marketed, mass-manufactured, one size fits all style treatment. Scientists formulating combination drugs face challenges in the development stages of multi-drug formulations such as compatibility issues among active ingredients and excipients affecting solubility and dissolution^[33] For prescribers, if one constituent of the combination is contraindicated for a patient, the product cannot be prescribed.^[34][35]

Illicit combination drugs are often formulated as a powder, paste, or counterfeit "pressed" pills intended to resemble their pharmaceutical-grade counterparts. Since 2018, ABC News of Houston reports that product described as "powder cocaine" originating from a clandestine laboratory are increasingly analyzed and found to contain other stimulants, in order to mimic cocaine's effects in a cost-effective, deceptive manner; many of the batches analyzed did not contain any cocaine or coca alkaloids whatsoever; instead, they were blends of various designer drugs, research chemicals, methamphetamine, and/or various amphetamines, derivatives, analogues; MDMA, caffeine powder, ephedrine or pseudoephedrine; levamisole, a flesh-eating veterinary antibiotic^[36]

Due to the crackdown of pill mills between 2007-2012, the opioid epidemic now includes preparations declared to be "heroin" or "pressed" replica pills of hydrocodone (sold Norco or LorTab); oxycodone (sold as Percocet), yet are rarely pure in their ingredient compositions. Cutting agents have grown in proportion to the overall composition of these products, such that "heroin" has been cut and mixed with central nervous system depressants including major tranquilizers such as quetiapine; muscle relaxants like carisoprodol or cyclobenzaprine; first-generation antihistamines like diphenhydramine or hydroxyzine); and benzodiazepine derivative and analogue research chemicals, including gidazepam, pinazepam, clobromazolam, etizolam). Since 2020, there has been a noticeable rise amongst active ingredients in opioid combinations containing fentanyl (more potent than heroin), and increasingly, carfentanil (an elephant and rhinoceros tranquilizer more potent than fentanyl).

Since 2023, worldwide samples of illicit combinations featuring opioids have contained the most lethal known substance to date: those belong to the nitazene chemical class.^[37] have been found in these opioid samples– all of which mimic the muscle relaxant, anxiolytic, and analgesic properties of pharmaceutical-grade opioid medications. U.S. Attorney General has indicated interested in federally regulating the relative mild veterinary sedative xylazine, which is currently available by prescription only, as a federally-controlled Schedule III controlled substance per the Controlled Substances Act,^[38] a direct response to its implication in overdose deaths featured in products alongside fentanyl and other power central nervous system depressants; xylazine is currently a controlled substance at the state level in Michigan and New York.^[39]

• Codrugs
• Synergy#Drug synergy

• Media related to Combination drugs at Wikimedia Commons