Phthalylsulfathiazole has roots stretching back to the golden age of antibiotic discovery, emerging in the early 1940s as infectious diseases struck fear across the globe. Its story started after German chemists unlocked the secrets of sulfonamides. They were racing to find compounds both potent against harmful bacteria and gentle enough for everyday patient care. By attaching a phthalic acid group to sulfathiazole, researchers got a molecule less likely to leave the stomach and more likely to focus its power in the digestive tract. World War II accelerated the need for weapons against dysentery and foodborne bugs, and phthalylsulfathiazole soon joined the battle. Hospitals and armies saw value in an orally-dosed, locally-acting remedy during a time where infections could spread rapidly in camps and barracks. Its clinical debut marked a significant leap in giving doctors more options when older drugs fell short or caused trouble.
This tablet, capsule, or powder does more than just sit on a shelf. Its primary role targets gut infections, especially those caused by shigella, salmonella, and other invaders eager to stir up trouble in the intestines. The compound shines brightest in treating bacterial dysentery and enteritis, where many systemic antibiotics can’t reach high enough concentrations in the gut to win the microbial war. Pharmacists often include it in combination regimens since its local action spares much of the rest of the body from side effects, and its broad coverage of Gram-negative and some Gram-positive bacteria helps patch holes in treatment plans. In markets where bacterial diarrhea still places a heavy burden on healthcare systems, it continues to anchor basic lists of antimicrobial drugs.
Phthalylsulfathiazole looks like a pale yellow or beige powder, with a fine, easy-to-handle consistency suited for mixing into tablets or capsules. At a molecular level, its formula reads C17H13N3O5S2, which puts it in the upper range for molecular weight among sulfonamides. Its melting point sits at about 203-206°C, and the substance doesn’t dissolve well in cold water, which partly explains its targeted gut action after oral intake. The molecule contains a phthalimide ring, thiazole segment, and a sulfonamide group, all fused into a structure sturdy enough to survive stomach acid but ready to do its work lower in the digestive tract. Scientists often notice its slight odor and bitter taste during manufacturing. Handling the powder in the lab means respecting its dustiness and potential to irritate the eyes, nose, or skin with prolonged exposure.
Phthalylsulfathiazole usually comes with purity minimums set between 98-99%, checked using modern analytical tools like HPLC or UV spectroscopy. Labels must display batch number, manufacturing date, and expiration period, along with any essential regulatory warnings about possible allergies or cross-reactivity with other sulfonamides. Packing manufacturers avoid moisture contamination by using sealed, opaque containers to prevent chemical breakdown, especially in hot or humid storage spaces. Tablets and capsules often contain 500 mg per dose, aligned with pharmacopoeial standards established by organizations such as the United States Pharmacopeia (USP) or the European Pharmacopoeia (Ph. Eur.). Labels warn of rare but serious side effects, including bone marrow suppression and hypersensitivity, reflecting modern regulatory guidance shaped by decades of pharmacovigilance data.
The synthesis of phthalylsulfathiazole starts with sulfathiazole, itself a product of reacting 2-aminothiazole with p-acetamidobenzenesulfonyl chloride. The next step takes this base molecule and brings it together with phthalic anhydride. The reaction happens in the right organic solvent—often pyridine—under gentle heating, knitting the phthalyl group to the amino function of sulfathiazole. The mixture cools, and crystals of phthalylsulfathiazole tumble out when water is added. Chemists then filter, wash, and dry the product, checking the color and melting point before weighing out doses for the next production stage. Yields tend to run high, but the process requires careful attention to temperature, timing, and purity of raw materials to avoid impurity build-up in the final batch.
The compound’s structure takes well to modification, with chemists exploring changes in the thiazole ring or swapping in different ring substituents to tweak antibacterial power or safety. Its sulfonamide group remains the key for activity, forming a competitive blockade at bacterial folic acid synthesis sites. In some labs, researchers run mild hydrolysis on phthalylsulfathiazole to see how quickly it converts back to active sulfathiazole or new metabolites, since breakdown rate changes how long the drug lingers in the gut. Adding different protecting groups or lengthening the phthalyl segment can shift solubility or absorption further, but most modifications try to preserve that crucial local effect while cutting down side reactions.
Ask across different countries or regulatory agencies, and you’ll hear phthalylsulfathiazole go by a handful of other names: phthalylsulphathiazole, sulphathalazole, and under trade names like Phthalazole or FTALAZOL. Pharmaceutical catalogs sometimes list it using its CAS number (85-73-4) for precise identification. In practice, doctors and pharmacists stick with the common name or the brand name most available on local hospital tenders or supplier contracts.
Anyone working with phthalylsulfathiazole needs to follow strict operational standards set by agencies such as OSHA, ECHA, and their national equivalents. Manufacturers set up dust extraction and containment at tablet presses and blending tanks, requiring operators to wear masks, gloves, and sometimes full gowns to avoid skin and eye contact. Pharmacies handle the finished product much like any sulfonamide, watching patient records for history of allergies, previous bone marrow problems, or kidney disease. Hospitals brief patients about warning signs—rash, persistent fever, sore throat—urging them to report problems quickly. Disposal of out-of-date or spilled compound often gets treated as hazardous pharmaceutical waste, incinerated at controlled temperatures so fragments don’t leach into the water supply.
Phthalylsulfathiazole draws most of its clinical value from treating infections of the lower digestive system. Gastroenterologists and infectious disease doctors prescribe it for simple and complicated bacterial diarrhea, especially after lab tests or clinical signs point to enteric pathogens. In veterinary medicine, it finds a place in managing outbreaks of colitis in cattle and poultry, since animals also face tough gastrointestinal bugs in crowded farm conditions. Some countries include it in travel medicine kits for relief from foodborne illness in areas where access to intravenous drugs or sophisticated lab testing is out of reach. It rarely makes an appearance in respiratory infections or in settings with newer, more targeted antimicrobials, but it remains useful in curbing resistance by sparing broad systemic agents.
Ongoing research keeps exploring ways to stretch phthalylsulfathiazole’s value in the modern pharmacological toolkit. Some scientists study its combinations with probiotics or gut-targeted anti-inflammatories to see if recovery times shorten or relapse rates drop in tough-to-treat cases. Others sift through data on resistant bacterial strains, searching for mutations that might dodge sulfonamides, then using that information to adjust dosing guidelines. Laboratory teams also try to develop formulations that release drug more predictably over time, using smart polymers or granulation techniques to improve patient adherence. With newer molecular biology tools, a few groups map the compound’s interaction with gut flora, aiming to minimize knock-on effects like secondary infections or imbalance in helpful bacteria.
Safety research on phthalylsulfathiazole paints a careful picture. Data show it poses less risk of kidney injury and crystal-induced blockages compared to some older sulfonamides, since its low absorption means it leaves much of the body untouched. Still, rare allergic reactions—from mild rashes to life-threatening anaphylaxis—can emerge, particularly in people sensitive to sulfa drugs. Bone marrow suppression appears with warning frequency in medical texts, demanding regular blood count checks for anyone on extended courses. In animal models, high doses sometimes knock out white blood cells or trigger neurological symptoms, pointing to a narrow toxicological window. Regulatory agencies keep updating acceptable daily intake and occupational exposure limits as new animal and clinical findings surface.
Looking forward, phthalylsulfathiazole stands at a crossroads. Newer, more specific antibiotics siphon demand in wealthy regions, but its reliability, cost-effectiveness, and proven track record offer a lifeline in low-resource settings. As antimicrobial resistance rises, the search for localized therapies could swing interest back to agents with gut-specific effects. Formulators and biotech startups eye possibilities to combine this drug with modern delivery systems, like nanoparticle encapsulation or intestine-focused timed-release matrices. Research may also open up non-human applications, from companion animal care to agricultural disease management. Its historical importance shows how well-understood drugs can reach a new generation of patients with the right updates—and a deep respect for medical history’s lessons.
Phthalylsulfathiazole, with a name that doesn’t roll off the tongue, has worked for decades as a go-to antibacterial medicine—especially in parts of the world where resources are tight and fast solutions matter. Doctors turn to it mostly for fighting infections in the gut, tackling trouble like dysentery, colitis, and some stubborn causes of diarrhea. This isn’t the first option pulled from the pharmacy shelf in countries with broad antibiotic access, but its value shows up in settings where advanced drugs carry big price tags or pose concerns over growing resistance issues.
This medicine doesn’t wander through the whole body. Instead, it zeroes in on the digestive tract since it isn’t absorbed from the intestines. That means fewer worries about effects elsewhere and puts its power right where the sick gut needs it. Many old-school antibiotics scatter to organs far and wide, tugging along side effects that leave you worn down or queasy. Phthalylsulfathiazole stays local, which keeps risks lower for folks already feeling rough.
There’s a real need to take resistance seriously in the world of antibiotics. Phthalylsulfathiazole came on strong during an age before bacteria learned to dodge the attacks of many medicines. Now, overuse—a big problem everywhere—has nudged more bacteria to outsmart it. Some experts blame loose regulations and leftover drugs sitting on medicine shelves at home.
Growing bacterial resistance isn’t theory anymore. The World Health Organization reports increased rates of gut infections that laugh in the face of older medicines, including this one. Street clinics in several countries report cases where this antibiotic no longer helps, which ends up risking the patient’s health and stretching the slim budgets of local hospitals. In places that stick with these medicines because buying newer ones just isn’t in the cards, the risk for treatment failure hangs heavy.
Working in a rural community clinic in the early 2000s, phthalylsulfathiazole would often show up at our small pharmacy. Patients came in with persistent diarrhea or cramping gut pain, and this was one of the few oral antibiotics stocked for intestinal infections. We all knew the script—avoid giving antibiotics for viral stomach bugs, save them for dangerous cases, and warn everyone not to cut the course short. But habits stick, and demand from worried parents can be strong. It’s tough to turn someone away when cheap treatment is trusted by the community, even if government warnings urge more cautious use.
Given time and experience, a pattern became obvious. Some kids bounced back fast, but others needed a change in prescription—proof that resistance doesn’t just live in science journals; it lands right at the clinic’s cracked linoleum floor.
Doctors and policy makers can reduce dependency on medicines like phthalylsulfathiazole only by pairing better diagnostic tools with public education. Fast stool tests, for instance, help figure out what type of infection sits at the core, so antibiotics don’t get tossed around like candy. Meanwhile, patients deserve to know when antibiotics help and when they harm.
Manufacturers can also look into safer, more targeted options, especially for places where new drugs are simply too expensive. If governments and nonprofits put effort into training programs and prescription oversight, antibiotics like this one could hold on as a backup rather than a first line of defense. Sharing accurate health information matters most—especially in communities where old habits and limited drug options meet the challenge of changing bacterial threats.
Phthalylsulfathiazole often pops up in conversations about gut infections or traveler’s diarrhea. It works as an antibiotic that mostly stays in the gut, which helps wipe out certain bacteria causing stomach problems. That local action brings relief, but it doesn’t come without some risk. Let’s not pretend otherwise—side effects come with many medicines, and this one demands respect, especially from people who feel antibiotics work like magic bullets.
Gastrointestinal issues go hand-in-hand with this drug. Nausea shows up quickly for some after a dose. It doesn’t always leave quietly, either. Vomiting, loss of appetite, and abdominal cramping: these symptoms knock on the door as the body adjusts to the medicine. Diarrhea can even worsen unexpectedly, which feels cruel when someone just wants the runs to stop. The irony isn’t lost on folks who try to patch up their gut and end up with more problems.
Allergic reactions don’t stay rare, either. Rashes, itching, or redness sometimes push people to call their doctor straight away. A wise move, since ignoring an allergic reaction never ends well. In rare cases, the problem turns serious—angioedema or even signs of Stevens-Johnson syndrome, where skin and mucous membranes blister. My own time in a hospital memory includes a middle-aged man who came for stomach pain and suddenly developed a rash and blistering. He got immediate care and turned out fine, but that’s a reminder not to dismiss skin changes when on any sulfonamide antibiotic, including phthalylsulfathiazole.
Blood changes sometimes hide until they show in a lab test. Leukopenia, thrombocytopenia, or even hemolytic anemia can appear, particularly in people with existing health conditions or those who take the drug for longer than a few days. Sulfonamides can knock down blood cell counts, even if someone feels fine. I have seen friends lose their appetite or get pale, thinking it’s nothing—until a blood test shows something deeper at play. That’s not rare drama, it’s the body’s quiet protest.
On rare occasions, folks report nervous system symptoms. Headache, sleepiness, or dizziness sneak in. Most people shrug them off, but for some, these symptoms linger or interfere with work. One time, a student confided that the brain fog after antibiotics made it almost impossible to focus in class. In hindsight, her medicine list included a sulfonamide.
Gut bacteria pay a price with each course. Phthalylsulfathiazole wipes out not just the villains, but the good ones too. Disrupted flora can trigger yeast overgrowth or bring on new infections. I remember a neighbor who celebrated his diarrhea relief, only to complain about burning from a yeast infection a few weeks later. Current clinical evidence supports these stories: antibiotics often shift the whole gut balance, not just the obvious symptoms.
Anyone on phthalylsulfathiazole owes it to themselves to pay attention: allergic reactions, new rashes, unexplained fevers, or fatigue should push people to reach out to their health team. Doctors today urge patients to finish courses as prescribed, to slow resistance, but personal monitoring matters just as much. People with a history of sulfa allergies or blood problems need to weigh in with doctors before starting this medicine. And gut health needs a long view, with probiotics or dietary support sometimes making a difference during or after treatment.
Phthalylsulfathiazole handles tough cases, but it’s not a free ride. Side effects deserve respect and real discussion, both between patient and doctor, and among people sharing their stories in waiting rooms or online. Knowledge pulls people out of confusion and gives them a path to honest decision-making.
Phthalylsulfathiazole often sits on the pharmacy shelf under different names, but one thing stands out: it’s a sulfonamide antibiotic. Doctors reach for it when the gut gets knocked out of balance by certain bacteria. Folks traveling, or those with stomach upsets brought on by questionable food or water, sometimes hear about it as a backup plan.
In my experience, popping antibiotics like candy never worked out for anyone. There’s always that temptation—maybe you want to feel better faster, maybe you’ve heard a neighbor swear by it. Still, following the doctor’s orders pays off every time. For Phthalylsulfathiazole, the dose your doctor picks depends on the type and intensity of your infection, plus your age and general health. Most adults start with 1 to 2 tablets, four times daily, after meals. The doctor usually sets a defined course, often around a week. Stopping midway through often means the infection sticks around longer or gets angry and harder to treat next time.
Any medicine can cause problems. I’ve seen folks shrug off a rash or an upset stomach—thinking it’ll pass. With Phthalylsulfathiazole, side effects sometimes creep in, and they deserve attention. That means keeping an eye out for hives, fever, or yellow skin and eyes. Sometimes, allergies to sulfa drugs cause trouble fast, and that needs quick medical help. Nausea, vomiting, or headache show up sometimes, too. My advice: keep your healthcare provider in the loop. There’s no bonus prize for toughing it out.
A doctor once told me, “Fluids keep everything moving.” Taking Phthalylsulfathiazole with a full glass of water helps your body flush out the drug and reduces the chances of kidney stones. Staying hydrated also helps your body cope with the infection itself. Folks with kidney or liver problems, or anyone on a complicated mix of medications, should double-check before starting something new.
It feels easy to stop antibiotics once you start to feel better. I remember someone close to me doing just that, only to end up sicker weeks later, now with germs no longer afraid of the medicine. Finishing the full round keeps bacteria from learning to dodge the treatment next time. That protects you and everyone else down the line.
Many people deal with leftover pills in the medicine cabinet. That’s risky—reusing or sharing ends up as a gamble no one wins. Pharmacies offer safe disposal solutions for unused antibiotics. Trusting the right source of medicine matters, too. Counterfeits lurk online, especially in countries with loose pharmacy rules. Stick to trusted and regulated pharmacies for peace of mind.
Phthalylsulfathiazole won’t work on viruses; don’t count on it for a cold or the flu. Some countries require a prescription. If you travel, check local rules. Some foods and supplements mess with antibiotics, so ask your doctor or pharmacist about any diet restrictions before starting therapy.
More folks using antibiotics responsibly means fewer superbugs in the future. I’ve seen communities change habits after awareness campaigns, leading to fewer hospital stays and fewer emergency room visits. Each of us gets a part to play by respecting prescriptions, finishing the course, and talking with our doctors about any side effects. It’s a small effort that helps everyone.
Walk into a pharmacy in many parts of the world, and you’ll notice strict shelves meant for antibiotics. For those used to popping into a clinic and walking out with a prescription, it feels routine. Phthalylsulfathiazole, a sulfa-based antibacterial, has found its place not only in medical textbooks but also in the medicine cabinets of certain countries. Yet, ask for it without a script in the United States or much of Europe, and you’ll be met with a firm “No.”
Rules differ a lot from country to country. In places like Russia and some sections of Eastern Europe, antibiotics sometimes line pharmacy counters like candy bars, with barely a question or raised eyebrow before the sale goes through. In other countries, you’ll notice pharmacists exercise more control, following strict regulations not just because of the law, but out of a concern for rising drug resistance. Growing up in a border town, I saw travelers smuggle in whole blister packs just to dodge their doctor’s desk. Where there are loopholes, the determined find them.
Phthalylsulfathiazole treats bacterial infections, especially in the gut. That’s appealing when food poisoning or traveler’s diarrhea hits, and waiting in a doctor’s lobby feels like a waste. But stories of using it for stubborn colds or mystery stomach pain pop up across forums and social feeds. That’s where trouble brews. Tossing antibiotics at viral infections doesn’t help; it just encourages bacteria to grow tougher. The World Health Organization lists antibiotic resistance among the greatest threats to global health. Misusing a drug like this, even with good intentions, chips away at the shield we rely on to keep infections in check.
Allergies, drug interactions, and wrong diagnoses haunt the world of self-prescribing. Years ago, I watched my neighbor nearly collapse from a rash after taking sulfa drugs gifted by a well-meaning relative. No one had asked about her allergies. No local pharmacist checked other meds she used daily. She ended up in the hospital.
Buying medications from online stores brings convenience, but not safety. Sellers offer phthalylsulfathiazole without asking for a prescription. Sometimes, these outlets sidestep national regulations, ship from secretive warehouses, and slap labels in languages few can read. One study in The BMJ showed fake or substandard drugs flooding these shady online markets, missing active ingredients or carrying dangerous contaminants. Taking those pills turns into a gamble.
Tighter rules and pharmacy crackdowns help, but people need solid information. It’s tempting to trust a neighbor who swears by a yellow box from overseas, or a website that guarantees fast shipping. Reality bites back hard if the wrong drug fuels resistance or triggers severe side effects. Healthcare providers should speak plainly about why prescription-only policies exist—not to frustrate patients, but to keep treatments working and communities safe. Access to trustworthy information in local languages deserves just as much attention as police checks or customs policies.
Asking about safe use and legal access points back toward one question: Are we doing enough to make sure people understand the risks and real benefits of antibiotics? Phthalylsulfathiazole, like all antibiotics, works best with oversight, honesty, and common sense—not as a souvenir from a distant pharmacy shelf or a late-night internet impulse buy.
Phthalylsulfathiazole often comes up in medical discussions about treating bacterial infections, particularly those affecting the gut. People look for quick fixes when experiencing uncomfortable symptoms, but not all antibiotics fit everyone’s situation. Doctors stress matching the right drug to the right patient, since one person's solution can turn into another's problem.
Sulfonamide allergies can range from hives to life-threatening reactions. Phthalylsulfathiazole belongs to the sulfa drug family, so anyone who has broken out in rashes or had trouble breathing after taking sulfa medications should leave this one alone. Reports show that about 3% of people on these drugs run into allergic reactions. Swelling, difficulty swallowing, and skin blistering don't count as minor side effects — they’re red flags that demand immediate medical attention.
Infants and toddlers process medicines in unique ways. Their bodies haven't developed the enzymes needed to break down certain compounds. Giving this drug to kids younger than the age of three has led to dangerous builds-up in the blood and serious complications. Pediatricians keep it off their list for this age group for a reason—safer, tested alternatives exist.
Doctors bring up the risks with pregnant women for good reason. Animal studies and a handful of older human trials have hinted at problems for unborn babies, especially during the last trimester. Babies could develop jaundice or other blood-related issues. For mothers who breastfeed, the drug can slip into the milk. Tiny traces sometimes pose risks for the baby too. People planning a pregnancy, already expecting, or actively breastfeeding should talk through options with their healthcare team instead of grabbing whatever’s within reach at the pharmacy.
The liver and kidneys handle most of the clean-up work after a person swallows medication. If either organ doesn’t function well, the drug can stick around too long and spark trouble — think vomiting, yellowing eyes, or confusion. Studies show patients with liver or kidney trouble run a greater risk of side effects or toxicity. Doctors keep a close eye and often turn to different treatments altogether for these patients.
Phthalylsulfathiazole messes with blood cells for some folks. People with conditions like anemia or low white blood cell counts stand on shaky ground here. If someone has a history involving bone marrow problems or rare blood diseases, health professionals usually steer clear of this drug.
Mixing this medicine with antidiabetic drugs, some blood thinners, or other sulfa medications can cause unpredictable reactions. These interactions might lead to low blood sugar, bleeding problems, or extra strain on the body’s filtration system. Pharmacists and doctors use detailed lists to check if something conflicts. Anyone taking regular prescription or over-the-counter meds should come clean about their complete list before starting antibiotics.
Many antibiotics work wonders in the right hands, but a mismatch can land patients in the hospital. Doctors rely on history, lab results, and allergy details to make safe choices. Pharmacies and clinics have a duty to ask tough questions before handing out medication. People shouldn't hide anything from medical staff or rush into self-diagnosis; protecting health sometimes means passing on a drug, not taking it.
| Names | |
| Preferred IUPAC name | 4-[(2-Sulfamoylphenyl)carbamoyl]benzenesulfonamide |
| Other names |
Phthalylsulfathiazole Phthalylsulphathiazole Sulphathiazole phthalyl Sulfathiazole phthalyl Phthalylsulfathiazolum Talasol |
| Pronunciation | /fthal-uhl-sul-fa-THAI-uh-zohl/ |
| Identifiers | |
| CAS Number | 85-73-4 |
| Beilstein Reference | 1207034 |
| ChEBI | CHEBI:8516 |
| ChEMBL | CHEMBL1401 |
| ChemSpider | 26721 |
| DrugBank | DB01332 |
| ECHA InfoCard | 100.008.826 |
| EC Number | EC 215-945-3 |
| Gmelin Reference | 85367 |
| KEGG | C07485 |
| MeSH | D010801 |
| PubChem CID | 4927 |
| RTECS number | WS2975000 |
| UNII | 263U589NW5 |
| UN number | UN2811 |
| CompTox Dashboard (EPA) | DTXSID7023209 |
| Properties | |
| Chemical formula | C17H13N3O5S2 |
| Molar mass | 383.40 g/mol |
| Appearance | White or yellowish crystalline powder |
| Odor | Odorless |
| Density | 1.7 g/cm³ |
| Solubility in water | Slightly soluble |
| log P | -1.14 |
| Acidity (pKa) | 2.02 |
| Basicity (pKb) | 6.94 |
| Magnetic susceptibility (χ) | -69.0·10⁻⁶ cm³/mol |
| Refractive index (nD) | 1.693 |
| Dipole moment | 5.8 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | Std molar entropy (S⦵298) of Phthalylsulfathiazole: 435 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -831.7 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -1562 kJ mol⁻¹ |
| Pharmacology | |
| ATC code | A07AB03 |
| Hazards | |
| Main hazards | Harmful if swallowed. Causes serious eye irritation. May cause respiratory irritation. |
| GHS labelling | GHS07, GHS09 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Hazard statements | H302: Harmful if swallowed. H319: Causes serious eye irritation. |
| Precautionary statements | Precautionary statements: "P261, P264, P270, P272, P273, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P363, P501 |
| NFPA 704 (fire diamond) | 2-1-0 |
| Flash point | 119°C |
| Autoignition temperature | 660 °C |
| Lethal dose or concentration | LD50 oral, rat: 13 g/kg |
| LD50 (median dose) | LD50 (median dose): 13,000 mg/kg (rat, oral) |
| NIOSH | Not Listed |
| PEL (Permissible) | Not established |
| REL (Recommended) | 1 g daily |
| IDLH (Immediate danger) | Not listed |
| Related compounds | |
| Related compounds |
Sulfasalazine Sulfanilamide Sulfathiazole Phthalic anhydride |
