Bactrim (Trimethoprim)

Common Use

Bactrim is a combination antibiotic that contains two active ingredients: sulfamethoxazole and trimethoprim. Together, they work by blocking two consecutive steps in the production of folic acid, which bacteria need to survive and multiply. Bacteria cannot absorb folic acid from their environment—they must produce it themselves. By blocking this process, Bactrim effectively stops the growth of many types of bacteria.

Bactrim is effective against a wide range of bacteria, including:

Streptococci – cause strep throat, pneumonia, and other infections

Staphylococci – cause skin infections, abscesses, and other conditions

Pneumococci – a common cause of pneumonia and ear infections

Bacillus dysentery – causes dysentery (severe diarrhea with blood)

Typhoid fever – a serious bacterial infection spread through contaminated food and water

E. coli – a common cause of urinary tract infections

Proteus – can cause urinary tract infections and kidney stones

Bactrim is not effective against:

Mycobacterium tuberculosis (causes tuberculosis)

Spirochetes (such as those that cause syphilis)

Pseudomonas aeruginosa (a type of bacteria that often causes hospital-acquired infections)

Bactrim is used to treat a variety of bacterial infections, including:

Pneumonia – including a type called Pneumocystis jirovecii pneumonia (PCP), which is common in people with weakened immune systems

Respiratory tract infections – such as bronchitis, sinusitis, and otitis media (ear infections)

Gastrointestinal system infections – such as traveler’s diarrhea and certain types of bacterial gastroenteritis

Urinary tract infections (UTIs) – including cystitis and kidney infections

Infections that develop after surgery (postoperative infections)

Skin and soft tissue infections – such as cellulitis and abscesses

Other bacterial infections as determined by a doctor

Dosage and Direction

Bactrim can be taken two or three times a day, with or without food—whatever suits you best. Take it with a glass of water to help prevent crystals from forming in the urine.

The dosage depends on the type and severity of the infection, your weight, and your kidney function

Patients with severe kidney failure require a dose adjustment (reduced dose or extended interval)

It is important to complete the full course of treatment, even if you start feeling better, to prevent the infection from returning and to reduce the risk of antibiotic resistance

Precautions

Avoid exposure to sunlight or tanning beds while taking Bactrim, as it can make your skin more sensitive to UV rays and cause severe sunburn

Antibiotic medicines can cause diarrhea. If you develop severe or persistent diarrhea, inform your doctor—this could be a sign of Clostridium difficile-associated colitis

Warn your doctor if you suffer from asthma or have severe kidney or liver disorders

Contraindications

Bactrim should not be used in the following situations:

Allergy to sulfamethoxazole, trimethoprim, or any other sulfonamide medications

Pregnancy – especially during the first trimester and near term, as it may affect the baby

Breastfeeding – the medication passes into breast milk and may affect the nursing infant

Anemia caused by folic acid deficiency (megaloblastic anemia)

Premature babies and newborns – especially those under 2 months of age

Severe liver or kidney impairment – unless dose-adjusted

Possible Side Effects

Seek immediate medical attention if you experience signs of a serious allergic reaction or severe adverse effects:

Hives, difficulty breathing, swelling of the face, lips, tongue, or throat

Fever, sore throat, and headache with a severe blistering skin rash (Stevens-Johnson syndrome)

Pale skin, easy bruising or bleeding (signs of blood disorders)

Diarrhea that is watery or bloody – may be a sign of C. difficile infection

Hallucinations

Slow heart rate, weak pulse

Nausea, stomach pain

Urinating less than usual or not at all (signs of kidney problems)

Common side effects may include:

Nausea, vomiting, loss of appetite

Mild diarrhea

Headache

Skin rash

Drug Interactions

Bactrim can interact with many medications. Inform your doctor about all prescription and non-prescription/herbal products you are using.

Important interactions:

Dofetilide – should not be co-administered with Bactrim due to risk of serious heart rhythm problems

Methenamine – should not be taken with Bactrim as it increases the risk of crystals in the urine

Anti-diabetic medications – Bactrim may increase the effect of certain diabetes drugs, leading to low blood sugar (hypoglycemia)

Blood thinners (such as warfarin) – Bactrim may increase the risk of bleeding; INR should be monitored

Cyclosporine – Bactrim may increase the risk of kidney problems

Digoxin – Bactrim may increase digoxin levels in some patients

Potassium-sparing diuretics (such as spironolactone) – Bactrim may increase potassium levels (hyperkalemia)

Live vaccines – Bactrim may reduce their effectiveness

Tricyclic antidepressants – may increase the risk of heart rhythm problems

Missed Dose

Never take a double dose of this medication. If you miss a dose and it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take extra to make up for a missed dose.

Overdose

If you have taken too much Bactrim, you may experience:

Dizziness or drowsiness

Nausea, vomiting, loss of appetite

Stomach pain

Headache

Yellowing of the skin or eyes (jaundice)

Blood in the urine

Fainting

In case of serious side effects, seek immediate medical help.

Storage

Store Bactrim at room temperature between 15–25°C (59–77°F), away from light and moisture. Keep it out of reach of children and pets.

Disclaimer

We provide only general information about medications, which does not cover all directions, possible drug interactions, or precautions. Information on this site cannot be used for self-treatment or self-diagnosis. Any specific instructions for a particular patient should be agreed upon with your healthcare adviser or the doctor in charge of your case. We disclaim reliability of this information and any mistakes it may contain. We are not responsible for any direct, indirect, special, or other indirect damage as a result of any use of the information on this site, nor for the consequences of self-treatment.

About Our Service Cydoctors.com is an online pharmacy based right here in Cyprus. We know that when a bacterial infection strikes, getting your antibiotic quickly and reliably is essential—so we’ve made our service straightforward, dependable, and built with your convenience in mind. Because we’re local to the island, we can arrange delivery in the shortest possible time. For our customers in Nicosia, Limassol, and Larnaca, we’re pleased to offer overnight delivery, so your Bactrim can be with you by the next day, ready to help you fight off that infection and get back to feeling like yourself again.