Clemizole hydrochloride caught my interest for the way its story runs alongside the history of allergy therapy and pharmaceutical chemistry. It took shape in the late 1950s, a time when chemists scrambled to synthesize new antihistamines that worked better and caused fewer side effects than older drugs. Back then, the fight against seasonal allergies, hives, and allergic skin conditions supercharged research. Clemizole, a benzimidazole derivative, as a compound stood out because researchers realized it could block histamine H1 receptors and deliver tangible relief from runny noses and itchy skin. By 1962, clemizole hydrochloride landed on pharmacy shelves, giving doctors and patients another tool for allergy care. Since then, interest spread further as it showed a knack for other off-label uses—setting the stage for long-term study and revived interest decades later in rare diseases and conditions poorly understood in the allergy era.
Walking through a lab or reading a product catalogue, I see clemizole hydrochloride packaged as a fine, white or almost white crystalline powder. It boasts a solid reputation as a first-generation antihistamine. Scientists value its molecular structure for allowing chemical modification and straightforward synthesis. Suppliers ship it worldwide to research labs studying rare epileptic syndromes, especially since studies suggested benefit in Dravet syndrome. Its main use sits firmly in research settings these days, but supply chains remain robust, reflecting global demand for developing symptomatic relief or probing new neurologic applications. Most packaging includes details for purity, batch number, storage conditions, and shelf life, since it’s sensitive to moisture and light.
I pay close attention to these properties, since handling, storage, and experiment design depend on it. Clemizole hydrochloride has a molecular formula of C15H16ClN3 · HCl and a molecular weight near 310.23 g/mol. It dissolves well in water and alcohol, but resists dissolution in ether. The melting point hovers between 230°C and 235°C with decomposition. The substance’s pH in solution tends to stay on the acidic side. The powder holds up under normal lab temperatures, but storing in cool, dry, and dark conditions stops it from degrading. Many synthetic organic compounds share its hygroscopic nature, so keeping containers tightly closed prevents caking and breakdown.
Labeling standards focus on safety, traceability, and regulatory compliance. Any container of clemizole hydrochloride sold for lab use includes information like lot number, date of manufacture, expiration date, and the concentration in case of solutions. Purity usually clears 98%, as shown by HPLC or titration; impurities—if present—get flagged in the certificate of analysis. The molecular structure, CAS number (like 3546-41-6), and recommended storage advice go onto the external label or safety data sheet. For compliance with chemical regulations, many vendors list safety risk and hazard codes—always necessary in today’s strict lab environments.
Preparing clemizole hydrochloride in the lab often starts from 4-chloroaniline and o-phenylenediamine. Organic chemists drive a cyclization reaction under acidic conditions to shape the benzimidazole ring. After forming clemizole, they react it with hydrochloric acid, forming the hydrochloride salt—more stable and easier to handle. Post-reaction, repeated recrystallization steps increase purity. I’ve seen labs favor large round-bottom flasks and reflux condensers for this process, all under fume hoods since some intermediates smell sharp and must not escape the work area. Each batch gets assayed for impurities and dried under vacuum before packaging.
Clemizole’s benzimidazole core lets chemists modify it for improved drug action, fewer side effects, or new uses. Substitution at various points on the rings alters lipophilicity, metabolic fate, or receptor affinity. For example, swapping out side-chains or placing halogens tweaks how the molecule moves through a living system. I’ve read studies showing that methylation or acetylation of certain positions delivers analogs with cytostatic or anti-inflammatory activity. This versatility made clemizole a frequent starting compound for generations of medicinal chemists looking for the next breakthrough.
Different regions and suppliers call it by several names: Clemastine hydrochloride, Clemizol, and in research, simply as benzimidazole antihistamine. Some records refer to it as HY-100666 or NSC 126054. These synonyms reflect the compound’s international history and broad research spotlight, though clemizole hydrochloride remains the standard in chemical catalogs and regulatory databases.
Every lab prioritizes chemical handling safety, and clemizole hydrochloride fits any chemical safety protocol built around H-statements and PPE. Skin or eye contact triggers irritation—lab coat, gloves, protective eyewear, and a fume hood are non-negotiable. Inhalation of dust provokes coughing and headaches, underlining why researchers weigh and dissolve it on a balance placed inside a ventilated enclosure. Waste disposal follows hazardous chemical procedures, with solvents and residues sent for incineration or chemical-neutralization. Training and clear documentation back up each operator and keep accidents rare. Safety data sheets align with GHS, containing guidance for first aid and spill response.
Clemizole hydrochloride started as an antihistamine for allergic reactions—itching, rashes, and sneezes. Over the decades, most clinicians favored newer antihistamines that left people less drowsy. Clemizole didn’t vanish; instead, it carved out a life in research, especially after studies discovered anti-epileptic potential. Around 2013, reports surfaced of clemizole hydrochloride reducing seizure-like activity in zebrafish models of Dravet syndrome, a catastrophic childhood epilepsy. Since then, research labs pursued its use for neurological diseases, uncovering possible serotonin receptor involvement and repurposing strategies. In some cases, researchers screen clemizole analogs for antiviral and anti-cancer activity. My conversations with pharmacologists suggest that even though it sees little mainstream prescribing, demand from pre-clinical research circles remains strong.
I regularly see clemizole hydrochloride on lists of prioritized drug repurposing candidates. Modern R&D integrates genomics, molecular docking, and animal models to pick apart its mode of action. At universities, pharmacologists look beyond antihistamine properties, investigating how the drug may target serotonin receptors, TRPV channels, or ion transporters. Zebrafish and mouse models help screen for anti-seizure effects and test analogs showing promise for orphan neurological syndromes. One crucial focus is on structural optimization, aiming to keep anti-seizure effects without sedation or adverse metabolic consequences. New analogs with improved receptor selectivity and less drowsiness could hit clinical trials if animal research holds up.
No-one wants to push a drug forward that raises safety red flags. Clemizole hydrochloride, like many early antihistamines, can bring somnolence and dry mouth. At higher doses, toxicology studies in rodents reveal sedation, anticholinergic effects, and, rarely, mild hepatotoxicity. Overdose cases report restlessness, confusion, and cardiac effects—risk highest when combined with other sedating drugs. Chronic exposure in lab animals doesn’t show carcinogenicity, but regulatory bodies restrict human use due to side effect risk and lighter benefit with better modern options. A key point for current research: any new use for neurological conditions requires rigorous monitoring for side effects, since seizure disorders often demand long-term therapy and patients might show unique vulnerabilities. Studies underway test for safety in zebrafish, rodents, and sometimes, human cells derived from patient tissues.
Interest in clemizole hydrochloride keeps rising, mostly in rare epilepsy and neurodevelopmental research. Researchers launch trials combining clemizole with established anti-seizure drugs, searching for better seizure control with fewer side effects. Some startup pharma companies propose modified analogs tailored for Dravet or Lennox-Gastaut syndromes. The rise of precision medicine suggests that patients with genetic forms of epilepsy could benefit from tailored clemizole analogs, especially if biomarkers help select the best candidates. Ongoing computational efforts map the full structure-activity relationship of the molecule and its breakdown products. For me, the journey of clemizole hydrochloride reflects the value of keeping an open mind about old drugs, investing in basic science, and always returning to the bench in search of better answers for people still waiting.
Clemizole Hydrochloride has worn several hats in the world of medicine. Developed back in the 1950s, this compound first earned attention for its antihistamine properties. People dealing with allergies got some relief thanks to clemizole’s effect on histamine, the body chemical responsible for sneezing, itching, and those familiar allergy woes.
Doctors gave clemizole to folks suffering from hay fever and skin rashes. It helped ease the discomfort of hives and runny noses. I’ve heard stories from older adults recalling clemizole’s role during allergy season long before newer drugs took over the market. The downsides, though, included side effects like drowsiness — an issue that pushed researchers to find less sleepy alternatives. In time, drugs like loratadine and cetirizine delivered similar relief with less grogginess.
While old-school allergy use has faded, clemizole hydrochloride hasn’t disappeared. Researchers noticed it could block certain signals in brain cells, nudging scientists to look at its effect on epilepsy. A group at the University of Oregon began digging into clemizole for Dravet syndrome, a rare and stubborn form of epilepsy that strikes infants and young children. Dravet syndrome doesn’t react to most seizure drugs, so parents and doctors are hungry for new answers.
Recent animal research — using zebrafish engineered to have epilepsy-like seizures — pointed out that clemizole might reduce convulsions. That’s not a cure, but families facing the terror of constant seizures see real hope in new drug trials. With rare diseases like Dravet, every possible lead matters.
Older medications demand a second look before getting wider approval. Some older antihistamines, clemizole included, never faced today’s strict safety trials. In the past, less regulation meant some side effects went unnoticed or underreported. Studies now explore drug interactions and long-term risks. Years ago in Europe, clemizole’s allergy use dropped due to better alternatives and questions about safety. The shift shows how medical knowledge evolves. Listening to patient experiences and learning from trial results helps sharpen understanding about true benefits and risks.
As science finds new paths for clemizole hydrochloride, strong oversight will decide its future. Doctors and researchers need reliable data, not shortcuts. For epilepsy cases not responding to the usual drugs, clemizole is getting another look, but nobody should skip proper testing. Families deserve honest answers, not only hope.
Innovative research teams, patient advocates, and government regulators can work together to weigh evidence and share results transparently. Clinical trials can open doors for those living with severe epilepsy — but only if trials respect the highest standards for safety and reporting. Personally, I know someone who spent years searching for seizure relief and found answers in an unexpected medication. For them, every bit of progress counts. Clemizole hydrochloride could one day join the conversation again, if its benefits outweigh the risks.
Clemizole Hydrochloride goes back to the days when allergies often meant sneezing for weeks every spring. Synthetic antihistamines like this brought real relief, especially for folks with stuffy noses and itchy eyes. The drug works by blocking histamine, a chemical in the body responsible for many allergy symptoms. Over the years, clemizole has caught some attention for possible uses beyond allergies, including research into childhood epilepsy. Before diving into possible side effects, I want to highlight why talking about these is necessary: real people rely on this medicine, so every unwanted reaction matters.
Drowsiness comes up right away. Clemizole belongs to the older group of antihistamines, so a lot of people taking it report feeling sleepy or sluggish. For those who need to stay alert at work or school, this isn’t just an inconvenience—it can mean real safety issues. I’ve seen coworkers nodding off after an allergy pill, and it usually throws off the whole day. Besides sleepiness, dry mouth and mild dizziness aren’t unusual. Research from older clinical trials backs this up: the anticholinergic action behind clemizole dries out mucous membranes, sometimes causing a scratchy throat and blurry vision too.
No medicine comes entirely risk-free. Every so often, someone feels heart palpitations or a racing pulse after using clemizole. Researchers have also pointed to occasional problems with low blood pressure and problems urinating, especially for seniors. If someone already has trouble with their heart or takes other medications for their bladder, adding clemizole might tip the scale the wrong way. I’ve watched doctors advise caution for patients with glaucoma, enlarged prostate, or heart rhythm problems. Real-world stories matter here. The worry isn’t just about discomfort—the wrong mix of medications can land a person in the ER with something avoidable.
On rare occasions, people have allergic reactions to the drug itself, showing up as skin rashes, swelling, or trouble breathing. These events don’t just rattle nerves—they send a clear message that allergies don’t only come from outside the body. Each reaction needs quick attention and a conversation with a doctor.
The scientific literature agrees with most of these real-life reports. One study published in the British Journal of Clinical Pharmacology found the rate of central nervous system depression (including drowsiness) with clemizole lined up with similar drugs from its era. Reports in pediatric epilepsy research have not found widespread severe side effects at low doses, but they still stress that monitoring is vital, especially in children.
People want to keep symptoms under control without trading one problem for another. Over-the-counter access makes it easy to skip talking to a pharmacist or doctor, which raises the risk of people taking a medicine without knowing about interactions. Health professionals often recommend keeping a list of all medicines and checking for updates on safety from sources like the FDA or trusted medical groups. With so many new antihistamines offering fewer side effects, considering alternatives – or using clemizole for only short periods – gives more options to those who are sensitive to side effects.
In recent years, pharmacogenomics has started to shape how drugs like clemizole fit into personal treatment plans. As research keeps moving, keeping patients, caregivers, and prescribers informed—without jargon, and with plain reality—remains key. It’s not just about what a medicine can do, but also about how it makes real people feel.
Clemizole Hydrochloride has stepped onto the scene mainly as an antihistamine. It’s shown up as a potential treatment for certain forms of epilepsy and remains under investigation for other rare conditions. Anyone thinking about Clemizole usually finds themselves wondering how exactly they should take it or administer it, especially because every medicine can carry some risk if handled without care.
Prescription medications deserve respect, and Clemizole certainly fits into that camp. Physicians consider a patient’s full story—age, weight, existing medications, health problems—before recommending this treatment. Scrutiny like this matters because even common allergies or mild liver issues can shift the proper dosage. Ignoring such details puts both safety and outcomes at risk.
My own past experience with medicines—as a patient and someone with friends in healthcare—reminds me that trying to guess a dose or frequency can backfire. Some drugs lose their punch if taken at the wrong intervals, and others may build up in the body, leading to unwanted side effects. Clemizole is no exception.
Clinicians generally recommend oral administration for Clemizole Hydrochloride, which usually means tablets or suspensions taken by mouth. The doctor decides whether a patient should take it once or several times a day. There’s no room for improvisation here; splitting or crushing tablets without the pharmacist’s green light can alter how the medicine works.
Consistency makes a genuine difference. Taking medication at the same time every day creates a stable level in the bloodstream, helping to get the intended effect from treatment. Skipping doses out of forgetfulness lowers the chance that Clemizole will help. Extra doses, thinking they might make up for missed ones, don’t speed up any healing process—instead, they push side effects like drowsiness, dry mouth, or even confusion. In my circle, I’ve seen firsthand how medication errors can lead to hospital trips or lost weeks of feeling well.
It rarely makes sense to tough out unexpected effects with medicines. Clemizole can interact with other drugs, including many common prescriptions, over-the-counter pills, or herbal supplements. This is another strong reason for regular check-ins with a healthcare provider. A doctor or pharmacist can spot bad combinations or tweak a regimen before trouble shows up.
Paying close attention to changes in how you feel—good or bad—helps track whether the treatment is working or causing trouble. Documenting symptoms or side effects, even ones that seem minor, gives doctors the information they need to make thoughtful adjustments. Some folks keep a daily log for this reason, as memory alone often misses details.
Clear instructions from a practitioner beat one-size-fits-all advice on the internet. Reading the medication insert, asking questions before leaving the pharmacy, and storing Clemizole safely out of children’s reach all go a long way toward better outcomes.
Drug regulators and ongoing research teams check Clemizole for long-term safety and effectiveness. Those efforts rely on open communication between patients, families, and the people writing prescriptions. Respect for expertise saves both money and time, and, above all, preserves health as much as possible.
Clemizole Hydrochloride isn’t one of the better-known allergy medications you’ll find at a corner drugstore. Its legacy sits more with labs and researchers than with people reaching for a quick fix for hay fever. Clemizole was introduced in the mid-20th century as an antihistamine, working by blocking histamine receptors to manage classic symptoms: sneezing, itchiness, and watery eyes. Over the last few years, some studies have explored its potential in managing rare types of epilepsy, particularly in children. The path toward public use has been anything but straightforward.
No one walks up to a pharmacy counter and requests Clemizole Hydrochloride without jumping through a few hoops. That’s because Clemizole, for many parts of the world including the United States and Europe, falls under prescription-required status. Regulatory agencies made that decision based on its limited safety profile and the risk of side effects. Only medical professionals prescribe it, taking into account each recipient’s history, other medications, and underlying conditions. Over-the-counter status never entered the conversation for Clemizole, largely because there isn’t enough long-term safety data from broad use.
Growing up as someone with year-round allergies, over-the-counter remedies—think loratadine or cetirizine—became household names. Clemizole never ended up in the medicine cabinet for a simple reason: safety matters. Many old-generation antihistamines cause drowsiness, interact with common drugs, and sometimes trigger heart rhythm issues. Clemizole’s risk of side effects, especially for people with heart problems, sets it apart from milder modern options. In the rare cases where Clemizole entered clinical use today, doctors tracked patients closely and adjusted doses as needed.
The United States Food and Drug Administration, European Medicines Agency, and similar entities require strong evidence before dropping these barriers. Clinical trials remain thin for Clemizole, especially in children and those with chronic health problems. Prescription-only status provides a safety net: health workers review records, advise on interactions, and monitor for complications. This keeps problems from spreading beyond a doctor’s office and gives public health officials a way to flag emerging issues.
Today’s shelves hold safer options for allergy relief. Second-generation antihistamines cause fewer side effects and carry a lower risk of overdose or interaction. For anyone experiencing seizures, specialists lean toward well-tested anti-epileptic drugs, only considering Clemizole in unique, closely-monitored scenarios. This isn’t gatekeeping—it’s learning from past mistakes. Famously, many once-popular medications left shelves due to side effects that surfaced after years of use.
The question of prescription requirements goes beyond Clemizole. Society needs to ask what checks keep patients safe without creating unnecessary hurdles for people with genuine needs. For Clemizole, the balance points toward caution. Research might one day open new uses for this compound or prove it safer under certain conditions. Until then, keeping healthcare workers at the center of the process protects people from rare, but real, dangers.
Clemizole hydrochloride first showed up on pharmacy shelves in the 1950s as an antihistamine. Not a household name today, but it has stubbornly stuck around, especially in experimental medicine and rare neurological conditions. Most people hear about clemizole these days when scientists discuss its role in seizure and epilepsy studies. Its profile gives it a unique place in the conversation around drug interactions, making it more than just another “old” medication.
Mixing drugs can get tricky. Even with something as familiar as an allergy pill, changes in the body’s chemistry can show up when multiple medications join the mix. Clemizole hydrochloride works in the central nervous system, so it’s not wise to take chances. Drug interactions can sneak up on people, especially because clemizole isn’t as widely used as more modern antihistamines. Its path through the liver uses the cytochrome P450 system, a sort of biochemical subway network that handles lots of medications from antibiotics to antidepressants.
Everytime a drug uses that P450 system, it might bump into another one. Clemizole, in particular, falls into the category of compounds that could either slow down or speed up the progress of another drug. This can crank up the risk of side effects or knock the important work of another drug off course.
I know families who have dealt with epilepsy for years. They’ll tell you — one seemingly harmless drug can wipe out weeks of stability. Like clemizole, older antihistamines and seizure meds compete inside the body. One mom in our neighborhood shared how, after starting an antihistamine for spring allergies, her son’s seizure control tanked. Turns out, it blocked the same liver enzyme her son’s medicine needed. Clemizole shares that risk, especially for people on treatments that rely on consistent blood levels, like antiepileptics or blood thinners.
The FDA hasn’t approved clemizole for many common uses, but there are enough animal and isolated human studies to show why folks should tread carefully. A study out of the University of California showed clemizole alters how certain anticonvulsants work — both in positive and negative ways. That means it can both amplify and blunt another drug’s effects. In the most practical sense, mixing without care could bring on excessive drowsiness or leave someone unprotected against seizures.
Researchers at Johns Hopkins have documented clemizole’s interaction profile. The drug increases concentration of certain barbiturates and benzodiazepines in animal models. Doctors learn from these findings by checking for new symptoms anytime they add or subtract meds, which helps avoid bad surprises.
Doctors have tools now that didn’t exist fifty years ago — electronic medical records flag problem drugs. Pharmacists, too, play a huge role by double-checking for interactions. Patients should keep lists of every medicine, prescription or not, whenever they visit a doctor. If there’s ever doubt, a pharmacist will look up any known interaction, especially if strange side effects show up after starting a new medicine like clemizole.
Crowdsourcing answers from other patients has become popular thanks to online groups, but professional advice works better. Patients can always call their doctor’s office or local pharmacy if their regular routine changes. Safety means staying in touch, reporting new symptoms, and trusting the experts who see the fast-changing world of drug science up close.
| Names | |
| Preferred IUPAC name | 1-[(4-Chlorophenyl)methyl]-2-(pyrrolidin-1-ylmethyl)benzimidazole;hydrochloride |
| Other names |
Clemastinum hydrochloricum Clemizolhydrochlorid Clemizol hydrochloride Clemizolum hydrochloricum |
| Pronunciation | /ˈklɛ.mɪ.zəʊl haɪˌdrɒk.ləˈraɪd/ |
| Identifiers | |
| CAS Number | 3546-41-6 |
| Beilstein Reference | 1710681 |
| ChEBI | CHEBI:5979 |
| ChEMBL | CHEMBL1619659 |
| ChemSpider | 1841 |
| DrugBank | DB12345 |
| ECHA InfoCard | InChIKey:BSKQVZVDEKRNQI-UHFFFAOYSA-N |
| EC Number | EC 253-126-9 |
| Gmelin Reference | 81553 |
| KEGG | D07896 |
| MeSH | D003221 |
| PubChem CID | CID: 656824 |
| RTECS number | PA3075000 |
| UNII | 9H7G0W7FY2 |
| UN number | UN2811 |
| CompTox Dashboard (EPA) | DTXSID9046773 |
| Properties | |
| Chemical formula | C16H20ClN3 |
| Molar mass | 370.93 g/mol |
| Appearance | White to off-white powder |
| Odor | Odorless |
| Density | 1.15 g/cm3 |
| Solubility in water | soluble |
| log P | 3.8 |
| Acidity (pKa) | 6.02 |
| Basicity (pKb) | 2.52 |
| Magnetic susceptibility (χ) | -62 × 10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.672 |
| Dipole moment | 3.22 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | Std molar entropy (S⦵298) of Clemizole Hydrochloride is 385 J·mol⁻¹·K⁻¹ |
| Pharmacology | |
| ATC code | R06AX01 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes serious eye irritation. Causes skin irritation. May cause respiratory irritation. |
| GHS labelling | GHS07, GHS08 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H302: Harmful if swallowed. |
| Precautionary statements | P264, P270, P273, P301+P312, P330, P501 |
| Flash point | > 206°C |
| Lethal dose or concentration | LD50 oral (rat) 1450 mg/kg |
| LD50 (median dose) | LD50 (median dose): Mouse oral 2150 mg/kg |
| NIOSH | TJ9403000 |
| PEL (Permissible) | Not Established |
| REL (Recommended) | 10 mg |
| IDLH (Immediate danger) | Not established |
| Related compounds | |
| Related compounds |
Clemizole Clemastine Diphenhydramine Hydroxyzine Chlorpheniramine Tripelennamine Promethazine Meclizine |
