Finding a loose white tablet marked H 49 can leave you unsure about what it is or whether it is safe to take. A refill may also look different from the tablets you received before, even when the prescription name is the same.
The H49 pill contains sulfamethoxazole 800 mg and trimethoprim 160 mg. It is a prescription combination antibiotic commonly called sulfamethoxazole/trimethoprim, SMX-TMP, TMP-SMX, or co-trimoxazole. Confirm any loose or unfamiliar pill with a pharmacist before taking it because an imprint search cannot confirm where the tablet came from or how it was stored.
What is the H49 pill?
The H49 pill is a double-strength sulfamethoxazole and trimethoprim tablet. These are the same active ingredients and strength found in Bactrim DS and Septra DS.
The tablet is white to off-white, oval, and about 19 mm long. It has H 49 on one side and a deep score line on the other.
| Feature | Details |
|---|---|
| Imprint | H 49 |
| Active ingredients | Sulfamethoxazole and trimethoprim |
| Strength | 800 mg/160 mg |
| Color | White to off-white |
| Shape | Oval with beveled edges |
| Size | 19 mm |
| Reverse side | Deep score line |
| Drug type | Combination antibiotic |
| Availability | Prescription only |
| Controlled substance | No |
| Common brand names | Bactrim DS and Septra DS |
More than one company has sold or repackaged tablets with the H49 imprint, so the National Drug Code (NDC) can vary. Check the pharmacy bottle for the company, NDC, lot number, and directions connected with your prescription.
Is H49 the same as Bactrim DS?
H49 is a generic double-strength sulfamethoxazole/trimethoprim tablet. Bactrim DS is a brand name for the same active ingredients and strength. The tablets can have different imprints, inactive ingredients, packaging, and manufacturers.
Is H49 a narcotic or painkiller?
H49 is an antibiotic and is not a narcotic, opioid, or controlled substance. It does not directly relieve pain. Pain caused by an infection may improve as the correct treatment controls that infection.
What is the difference between H49 and H48?
H49 and H48 contain the same 2 active ingredients at different strengths:
| Imprint | Appearance | Strength |
|---|---|---|
| H 49 | White to off-white oval tablet | 800 mg/160 mg |
| H 48 | White to off-white round tablet | 400 mg/80 mg |
The difference in strength matters. Check the full imprint and prescription label before taking either tablet.
What is the H49 pill used for?
Sulfamethoxazole and trimethoprim treat infections caused by certain bacteria. A prescriber may use this combination for:
- Urinary tract infections (UTIs)
- Certain middle ear infections in children
- Certain flare-ups of chronic bronchitis in adults
- Shigellosis
- Traveler’s diarrhea caused by susceptible bacteria
- Treatment or prevention of Pneumocystis jirovecii pneumonia
Doctors may also prescribe it for certain skin and soft-tissue infections, including some caused by methicillin-resistant Staphylococcus aureus (MRSA). The choice depends on the suspected bacteria, test results, and local resistance patterns.
Is H49 a strong antibiotic?
The usefulness of H49 depends on the infection and whether the bacteria are sensitive to sulfamethoxazole/trimethoprim. It may work well against one infection and have little effect against another. A urine culture, wound culture, or another laboratory test may guide treatment when resistance is a concern.
Is H49 a sulfa drug, amoxicillin or penicillin?
H49 contains sulfamethoxazole, a sulfonamide antibiotic often called a sulfa drug, plus trimethoprim. It is not amoxicillin or a penicillin antibiotic. A person with a penicillin allergy may still have a separate sulfa allergy or another medical reason that makes H49 unsuitable.
Does H49 treat colds or the flu?
H49 does not treat colds, influenza, or other viral infections. Using an antibiotic when it is not needed can cause side effects and increase antibiotic resistance.
How does the H49 pill work?
Bacteria need folate to grow and survive. Sulfamethoxazole and trimethoprim block 2 different steps that bacteria use to produce folate. Blocking both steps can stop susceptible bacteria from multiplying.
Can H49 treat a UTI?
Sulfamethoxazole/trimethoprim can treat some bladder and urinary tract infections. The bacteria must be sensitive to it, and resistance rates differ by location.
Burning during urination does not always mean a simple UTI. Similar symptoms can occur with kidney infections, sexually transmitted infections, stones, and other conditions. Seek prompt medical care for urinary symptoms if you have fever, vomiting, back or side pain, blood in the urine, worsening symptoms, or are pregnant.
Can H49 treat a tooth infection?
H49 is not a routine treatment for ordinary tooth pain. Most dental pain and localized swelling need dental treatment, such as drainage, a root canal, or treatment of the damaged tooth.
The American Dental Association recommends dental treatment for most tooth pain and swelling. A dentist may prescribe an antibiotic when an infection has spread or causes signs such as fever or feeling generally unwell. Do not use leftover H49 tablets for tooth pain.
Can H49 treat chlamydia?
H49 is not a CDC-recommended treatment for chlamydia. The CDC chlamydia treatment guidance lists doxycycline as the recommended treatment for most adolescents and adults. Azithromycin or levofloxacin may be used in certain situations.
Testing matters because chlamydia may cause no symptoms and can occur with other sexually transmitted infections. If a test confirms chlamydia, recent sexual partners need evaluation, testing, and treatment.
H49 dosage and how to take it safely
The numbers 800 mg/160 mg describe the strength of one H49 tablet. They do not tell every patient how often to take it or how many days treatment should last.
For some infections, an adult may be prescribed one double-strength tablet every 12 hours. The correct schedule depends on the infection, kidney function, age, laboratory results, and other medicines. Pneumocystis pneumonia requires a different dosing plan. Follow the directions printed on your prescription label.
These steps can reduce medication errors and some side effects:
- Take each dose at the prescribed time.
- Swallow the tablet with a full glass of water.
- Drink enough fluids during treatment unless a clinician has limited your fluid intake.
- Finish the prescribed course, even if you begin to feel better.
- Do not share the medicine or save leftover tablets for another illness.
- Use sunscreen and protective clothing because the medicine can make your skin more sensitive to sunlight.
- Split the scored tablet only when your prescription directions or pharmacist tell you to do so.
Children need a dose based on their weight and the infection. Sulfamethoxazole/trimethoprim should not be given to babies younger than 2 months. Kidney problems may require a lower dose or a different dosing interval.
Can you take H49 with food?
You can usually take H49 with or without food. Taking it with food may reduce nausea or stomach discomfort. Drink enough water because this can reduce the chance of crystals forming in the urine.
Can you drink alcohol while taking H49?
Evidence for a direct interaction is limited, though reactions involving flushing, nausea, vomiting, a fast heartbeat, or low blood pressure have been reported. Alcohol may also worsen dizziness or dehydration. The safest choice is to avoid it during treatment or ask your pharmacist about your situation.
How long does H49 take to work?
You may not feel better after the first dose. Symptoms often take a few days to improve, depending on the infection and its severity. Contact the prescriber if symptoms worsen or do not improve within the time they gave you.
H49 pill side effects
Some medication side effects are mild, but this medicine can cause rare and serious reactions. The difference between a side effect and an allergic reaction matters because a new rash needs prompt medical advice.
| What you notice | What to do |
|---|---|
| Nausea, vomiting, reduced appetite, or mild diarrhea | Contact the prescriber if it is severe, persistent, or prevents you from taking fluids |
| Headache, tiredness, or increased sun sensitivity | Ask a pharmacist or prescriber if it continues or interferes with normal activity |
| Any new rash | Stop taking H49 and contact the prescriber immediately |
| Blisters, peeling skin, painful rash, mouth sores, or red and irritated eyes | Get urgent medical care |
| Facial or throat swelling, trouble breathing, fainting, or collapse | Call 911 |
Severe skin and allergic reactions
Sulfamethoxazole/trimethoprim has been linked to Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS), and other severe skin reactions. Stop taking H49 and contact the prescriber immediately if a new rash or another sign of a serious reaction appears. Get emergency help for blistering or peeling skin, swelling of the face or throat, or trouble breathing.
Severe or delayed diarrhea
Antibiotics can allow Clostridioides difficile, often called C. diff, to grow in the intestines. Severe watery or bloody diarrhea, fever, and stomach cramps can begin during treatment or even 2 months or more after the last dose. Contact a clinician promptly. Do not treat severe diarrhea with an over-the-counter product unless a clinician tells you to do so.
Other symptoms that need medical care
Contact a healthcare professional promptly if you develop:
- Unusual bruising, bleeding, fever, sore throat, or mouth sores
- Yellow skin or eyes, dark urine, or severe upper abdominal pain
- Less urine, swelling, or sudden weight gain
- Muscle weakness, tingling, confusion, or an irregular heartbeat
- New or worsening cough, fever, chest pain, or trouble breathing
- Severe fatigue, pale skin, or repeated infections
These symptoms may point to a blood disorder, liver injury, kidney injury, an electrolyte problem, or a lung reaction.
Who should avoid H49 or speak with a clinician first?
Check these conditions with a prescriber before taking H49. Some make the medicine unsafe, and others may require closer monitoring.
When H49 should not be used
Do not take H49 if you:
- Have an allergy to sulfamethoxazole, trimethoprim, or a sulfonamide antibiotic
- Previously developed immune thrombocytopenia, a serious drop in platelets, after taking trimethoprim or a sulfonamide
- Have megaloblastic anemia caused by low folate
- Have severe liver damage
- Have severe kidney problems that cannot be monitored
- Have porphyria or thyroid dysfunction
- Take dofetilide
H49 must not be given to a baby younger than 2 months.
Conditions to discuss before taking H49
Tell the prescriber before starting H49 if you have:
- Kidney or liver disease
- G6PD deficiency, an inherited enzyme condition
- Low blood cell or platelet levels
- High potassium or low sodium
- HIV or AIDS
- Poor nutrition or a folate deficiency
- A history of severe allergies or asthma
Tell the prescriber about every medical condition before starting treatment. Blood tests, kidney tests, or potassium monitoring may be needed for some patients.
Pregnancy and breastfeeding
Tell the prescriber if you are pregnant, may be pregnant, or are planning a pregnancy. Sulfamethoxazole/trimethoprim can affect folate metabolism and may pose risks during pregnancy. The decision depends on the infection, stage of pregnancy, available treatments, and the risk of leaving the infection untreated.
Breastfeeding advice depends on the baby’s age and health. Extra caution is needed if the baby was premature, is jaundiced or ill, is younger than 2 months, or has G6PD deficiency. Ask the baby’s clinician and your prescriber before breastfeeding during treatment.
Children and older adults
For children aged 2 months and older, the dose depends on weight and the infection.
Older adults may have a greater chance of kidney problems, high potassium, folate deficiency, low platelets, and drug interactions. Their prescriber may order blood tests or change the dose.
H49 drug interactions
Sulfamethoxazole/trimethoprim can change the effects or blood levels of several medicines. Some combinations need closer monitoring, a dose change, or a different antibiotic. This table covers major examples, not every possible interaction.
| Medicine or group | Possible concern |
|---|---|
| Dofetilide | Do not take these medicines together; the combination can cause a dangerous heart rhythm |
| Warfarin | Stronger blood-thinning effect and a higher bleeding risk |
| Methotrexate | Higher risk of bone marrow problems and other serious side effects |
| Phenytoin | Higher phenytoin levels and side effects |
| ACE inhibitors, ARBs, spironolactone, or other potassium-raising medicines | High potassium levels, especially in older adults and people with kidney disease |
| Digoxin | Increased digoxin levels, especially in older adults |
| Cyclosporine | Kidney injury |
| Certain diabetes medicines | Low blood sugar |
| Thiazide diuretics | Increased risk of low platelets in some older adults |
| Leucovorin during Pneumocystis pneumonia treatment | Reduced treatment effect in certain patients |
Give the prescriber and pharmacist a complete list of your medicines and supplements. Do not start a new medicine during treatment without checking for interactions.
What should you do after missing an H49 dose?
Take the missed dose when you remember it. If it is almost time for the next dose, skip the missed one and continue with the regular schedule. Do not take 2 doses at the same time.
Ask a pharmacist when you are unsure whether the next dose is too close.
What should you do after taking too much H49?
Call Poison Control at 1-800-222-1222 in the United States if someone may have taken too much. Call 911 if the person collapses, has a seizure, cannot be awakened, or has trouble breathing.
Possible overdose symptoms include vomiting, loss of appetite, dizziness, confusion, blood in the urine, yellow skin or eyes, severe drowsiness, or loss of consciousness. Do not make the person vomit unless a medical professional instructs you to do so.
Was the H49 pill recalled?
A California Board of Pharmacy notice shows that Aurobindo Pharma recalled 3 batches of sulfamethoxazole/trimethoprim 800 mg/160 mg tablets in 2020 after metal was found in one tablet from each batch. The recall covered NDC 65862-420-05 and these batches:
| Batch | Expiration |
|---|---|
| STSD19109-A | 05/2022 |
| SP1D19083AA3 | 08/2022 |
| SP1D19084AA3 | 08/2022 |
Those batches are expired. The notice did not cover every H49 tablet.
If you are concerned about a current prescription, check the NDC and lot number on the original bottle or contact the dispensing pharmacy. Recall information can change, so verify it through the pharmacy or the FDA drug recall page.
How to store and dispose of H49 tablets
Store H49 tablets at room temperature in a closed container away from moisture and light. Keep them out of reach of children and pets.
Use a pharmacy or community medication take-back program for unused tablets. Ask a pharmacist about local disposal options when a take-back location is unavailable.
Medical disclaimer
This information is for general education and does not replace medical advice, diagnosis or treatment. Take prescription medication only as directed by a licensed healthcare professional. Contact a pharmacist or prescriber with questions about your dose, side effects, interactions, pregnancy, or breastfeeding.
References
- DailyMed: Sulfamethoxazole and Trimethoprim Tablet
- Drugs.com: H 49 Pill Identifier
- Drugs.com: Sulfamethoxazole and Trimethoprim
- Mayo Clinic: Sulfamethoxazole and Trimethoprim
- Cleveland Clinic: Sulfamethoxazole and Trimethoprim Tablets
- WebMD: Sulfamethoxazole/Trimethoprim
- CDC: Chlamydial Infections Treatment Guidelines
- American Dental Association: Antibiotics for Dental Pain and Swelling
- California Board of Pharmacy: Aurobindo Recall Notice
- FDA: Drug Recalls
- Infectious Diseases Society of America: Skin and Soft-Tissue Infections
- National Institute on Alcohol Abuse and Alcoholism: Alcohol-Medication Interactions