Sulfamethoxazole/Trimethoprim (Intravenous)

Sulfamethoxazole and trimethoprim combination is used to treat urinary or intestinal tract infections. It can also be used to treat pneumocystis carinii


Sulfamethoxazole and trimethoprim combination is an antibiotic drug that is used in the treatment of certain urinary or intestinal tract infections. It can also be used to treat pneumocystis carinii pneumonia (PCP). Pneumocystis carinii pneumonia is seen most commonly in patients whose immune systems are compromised, such as cancer patients, patients with acquired immune deficiency syndrome (AIDS), and transplant patients.

Sulfamethoxazole and trimethoprim combination works by killing and therefore eliminating the harmful bacteria that can cause many different types of infections. However, this drug is not designed for the treatment of common colds, influenza, or other viral infections.

Sulfamethoxazole and trimethoprim combination is only available on prescription from your doctor and comes in solution form for intravenous administration.

Conditions treated

  • urinary tract infections
  • intestinal tract infections
  • pneumocystis carinii pneumonia (PCP)

Type of medicine

  • antibiotic
  • solution for intravenous use

Side effects

The use of sulfamethoxazole and trimethoprim combination is intended to eliminate bacterial infections, however you may experience some unwanted side effects while you are taking it. Before you commence using sulfamethoxazole and trimethoprim combination, be sure to inform your doctor about any allergic reactions that you have experienced while taking any other drugs. You should also mention any health problems or bad reactions that you have had when taking over-the-counter products, including herbal remedies or vitamin supplements.

Some medications may contain animal derivatives, preservatives or dyes and you must mention to your doctor if you have any known allergies to any of these.

The side effects that are outlined below are known to sometimes occur in patients taking sulfamethoxazole and trimethoprim combination. However, it is important to note that this list is not exhaustive. If you notice any of the following side effects or if you begin to feel unwell while taking this medication, you must consult your doctor straight away:

  • yellow eyes or skin
  • wheezing
  • weight gain
  • weakness or heaviness of legs
  • weakness in hands or feet
  • vomiting of blood
  • unusual weight loss
  • unusual tiredness or weakness
  • unusual bleeding or bruising
  • unpleasant breath odor
  • tinnitus
  • tightness in chest
  • swollen or painful glands
  • swelling or inflammation of the mouth
  • swelling of face, hands, legs, and feet
  • stomach pain
  • stiff neck or back
  • soreness of muscles
  • sore throat
  • shakiness and unsteady walk
  • severe diarrhea, which may also be bloody
  • scaly skin
  • redness, swelling, or soreness of tongue
  • redness of the white part of the eyes
  • red skin lesions, often with a purple center
  • red irritated eyes
  • rash
  • rapid heart rate
  • raised red swellings on the skin, the buttocks, legs or ankles
  • puffiness or swelling of the eyelids or around the eyes, face, lips or tongue
  • problems with muscle control or coordination
  • pinpoint red spots on skin
  • pale-colored stools
  • pale skin
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • painful knees and ankles
  • pain, tenderness, or swelling of foot or leg
  • pain or burning while urinating
  • numbness or tingling in hands, feet, or lips
  • not able to pass urine
  • nosebleeds
  • nausea
  • muscle or joint pain
  • lower back or side pain
  • loss of heat from the body
  • loss of appetite
  • large, flat, blue or purplish patches in the skin
  • joint or muscle pain
  • irregular heartbeat
  • indigestion
  • increased thirst
  • increased blood pressure
  • hives or itching
  • hearing loss
  • headache
  • hair loss
  • feeling tired or weak
  • general feeling of discomfort or illness
  • general body swelling
  • fever with or without chills
  • fainting spells
  • dizziness or lightheadedness
  • difficulty swallowing
  • difficulty breathing
  • decreased frequency or amount of urine
  • crawling, itching, numbness, painful, prickling, "pins and needles", or tingling feelings
  • cough or hoarseness
  • convulsions
  • constipation
  • confusion
  • clumsiness or unsteadiness
  • cloudy or dark urine
  • chills
  • chest pain
  • changes in skin color
  • burning of face or mouth
  • bluish-colored lips, fingernails, or palms
  • blood in urine or stools
  • bloating
  • blistering, peeling, or loosening of skin
  • blindness or vision changes
  • bleeding under the skin
  • bleeding gums
  • black, tarry stools
  • back, leg, or stomach pains
  • abdominal tenderness

If you do start to suffer from any of the following side effects when you begin taking sulfamethoxazole and trimethoprim combination, you may find that they resolve themselves within a few days, as your body gets used to the new medicine. In the meantime, your doctor or pharmacist may be able to suggest ways in which you can prevent or reduce some of the more bothersome side effects that are affecting you:

  • trouble sleeping
  • trouble concentrating
  • pain in the stomach, feeling over-full
  • sleeplessness
  • severe sunburn
  • sensation of spinning
  • seeing, hearing, or feeling things that are not there
  • redness or other discoloration of skin
  • passing of gas
  • nervousness
  • loss of interest or pleasure
  • lack of feeling or emotion
  • irritability
  • skin more sensitive to sunlight than usual
  • hives or welts
  • feelings of discouragement
  • feeling sad or empty
  • feeling of constant movement of self or surroundings

You should be reassured that not all patients experience side effects when taking sulfamethoxazole and trimethoprim combination, but you should always consult your doctor if you have any concerns about any unusual effects that you do experience.


You will be given this medication by a nurse or other trained medical practitioner. The drug is given through a needle placed into one of your veins. The drug is given via slow infusion over a duration of 60 to 90 minutes. The dose is calculated based on the condition for which you are being treated, your body weight, and your response to the treatment.

In the event that you are self-administering this medication, check that the liquid does not contain any particles of discoloration. If it does, contact your doctor for a fresh prescription.

While taking this medication you should drink plenty of water to reduce the risk of you developing kidney stones.

This medication is most effective when used at evenly spaced times during the day. If possible, try to ensure that you use the medicine at the same time each day. Use the whole course of medication, even if you start to feel better after a few days. If you stop taking the drug too early, the bacteria may continue to grow and your infection could return.

If you start to feel worse or your condition does not improve, ask your doctor for advice.

The recommended dosage of this medicine will vary between patients. Always take your medication as per your doctor's instructions or refer to the directions on the dispensed product pack.

In the event that you miss a dose of your treatment, take the medication as soon as possible. Do not double-dose. If it is very close to the time of your next scheduled dose, omit one dose and resume your usual regimen.

Drug interactions

Although there are some drugs that should never be used in tandem, in some cases it may be appropriate to use multiple different drugs, even though an interaction may occur. Your doctor will decide whether to adjust the dose or may suggest that you take other precautions.

If you are prescribed sulfamethoxazole and trimethoprim combination and you are already taking other medication, including herbal preparations, vitamin supplements or over-the-counter medicines, tell your doctor immediately.

Some foodstuffs should be avoided when taking certain types of medication, as should consuming alcohol and tobacco, as interactions may occur. Discuss with your doctor the possible implications of eating, consuming alcohol, and tobacco products with sulfamethoxazole and trimethoprim combination before you begin taking it.

Taking sulfamethoxazole and trimethoprim combination with any of the following medications is not recommended. Because of this, your doctor may decide to change some of your other drugs.

  • dofetilide
  • levomethadyl
  • methenamine

It is not generally recommended to use sulfamethoxazole and trimethoprim combination with the following drugs. However, your doctor may prescribe both medicines together with alterations to the dose and frequency of one or more of them:

  • Zotepine
  • Zofenopril
  • Warfarin
  • Vasopressin
  • Valsartan
  • Trimipramine
  • Trifluoperazine
  • Triamterene
  • Trandolapril
  • Telmisartan
  • Telithromycin
  • Tedisamil
  • Sultopride
  • Spironolactone
  • Spiramycin
  • Sotalol
  • Sertindole
  • Sematilide
  • Risperidone
  • Ramipril
  • Quinidine
  • Quinapril
  • Pyrimethamine
  • Propafenone
  • Prochlorperazine
  • Procainamide
  • Probucol
  • Prajmaline
  • Pirmenol
  • Perindopril
  • Pentamidine
  • Olmesartan Medoxomil
  • Octreotide
  • Nortriptyline
  • Moexipril
  • Methotrexate
  • Mercaptopurine
  • Mefloquine
  • Losartan
  • Lorcainide
  • Lisinopril
  • Lidoflazine
  • Leucovorin
  • Isradipine
  • Isoflurane
  • Irbesartan
  • Imipramine
  • Ibutilide
  • Hydroquinidine
  • Halothane
  • Haloperidol
  • Halofantrine
  • Gemifloxacin
  • Fosinopril
  • Foscarnet
  • Fluoxetine
  • Fluconazole
  • Flecainide
  • Erythromycin
  • Eprosartan
  • Eplerenone
  • Enflurane
  • Enalaprilat
  • Enalapril
  • Eltrombopag
  • Droperidol
  • Doxepin
  • Dolasetron
  • Disopyramide
  • Digoxin
  • Dibenzepin
  • Desipramine
  • Clarithromycin
  • Cholera Vaccine, Live
  • Chlorpromazine
  • Chloroquine
  • Chloral Hydrate
  • Ceritinib
  • Captopril
  • Candesartan Cilexetil
  • Bretylium
  • Benazepril
  • Azimilide
  • Azilsartan Medoxomil
  • Azilsartan
  • Azathioprine
  • Astemizole
  • Arsenic Trioxide
  • Aprindine
  • Amoxapine
  • Amitriptyline
  • Amiodarone
  • Amiloride
  • Ajmaline
  • Acenocoumarol
  • Acecainide

Taking sulfamethoxazole and trimethoprim combination in combination with any of the following medications could cause an increased risk of some side effects. Your doctor may alter the dose or the frequency of use of your medicines to mediate this:

  • Tolbutamide
  • Rosiglitazone
  • Rifabutin
  • Repaglinide
  • Phenytoin
  • Fosphenytoin
  • Didanosine
  • Anisindione
  • Amantadine
  • Acetohexamide

Some medication interacts with some foods, alcohol or tobacco. Tell your doctor if you have a preference for eating certain types of foods, if you use tobacco, or if you drink alcohol. Note that ethanol can cause certain side effects when used with sulfamethoxazole and trimethoprim combination.


Take sulfamethoxazole and trimethoprim combination exactly as instructed by your doctor. Do not intentionally take more than you are prescribed or take it more frequently than you have been told to. If you take too much of the medication, the side effects may be increased.

You should mention any existing health conditions that you have to your doctor before you start taking sulfamethoxazole and trimethoprim combination.

Studies have shown that sulfamethoxazole and trimethoprim combination can present a risk to the fetus. If you are pregnant, tell your doctor immediately before beginning your course of treatment. While you are taking this medication, use effective contraceptive methods to ensure that you do not become pregnant.

Research has shown that this medication can pass into breast milk. Do not breastfeed or express breast milk for later use while taking this medication. Ask your midwife or doctor for advice on alternative feeding options for your baby until you have finished your course of treatment with sulfamethoxazole and trimethoprim combination.

If you suffer from any existing medical conditions, you should tell your doctor before commencing treatment with this medication, especially the following:

  • Sulfamethoxazole and trimethoprim combination must not be used in patients who are suffering from megaloblastic anemia.

The medication should be used with caution in patients who have a history of the following medical conditions:

  • asthma
  • folate deficiency
  • glucose-6-phosphate dehydrogenase (G6PD) deficiency
  • HIV or AIDS
  • liver disease
  • kidney disease
  • seizures

This medication can sometimes cause severe side effects. You should contact your doctor immediately if you experience any of the following effects:

  • skin rash
  • very pale or yellow skin color
  • skin with purple spots
  • sore throat
  • fever
  • muscle pains
  • breathing problems
  • cough

Consult your doctor immediately if you begin to experience the following symptoms that could be signs of a serious intestinal infection:

  • stomach cramps
  • bloating
  • watery or severe diarrhea
  • bloody diarrhea
  • nausea
  • vomiting
  • ¬†unusual weakness or feeling tired

In some people, sulfamethoxazole and trimethoprim combination can cause anaphylaxis. This condition is very serious and can sometimes be fatal if not treated immediately. The following symptoms are indicative or anaphylaxis:

  • rash
  • swelling of the tongue and throat
  • breathing difficulties
  • shortness of breath
  • chest pain

These symptoms usually occur within a few minutes of the injection. If you are receiving this treatment in hospital, alert your nurse immediately. If you are at home, call 911.


Always keep your supply of sulfamethoxazole and trimethoprim combination in a sealed, airtight container and keep it at room temperature. Do not freeze this medication.

Do not leave this medicine in direct sunlight or where it could be exposed to heat or moisture.

Keep the medication well away from children and pets. In the event that a pet consumes sulfamethoxazole and trimethoprim combination, seek veterinary advice immediately.

Do not use sulfamethoxazole and trimethoprim combination that has passed its use-by date, if the packaging appears to be damaged or opened, or if the solution is cloudy or contains floating particles.

Ask your doctor or pharmacist for advice on how to dispose of any out-of-date medication. Never flush leftover solution down the toilet or drain, or throw it out with your trash where it could be discovered and eaten by children or animals.


Sulfamethoxazole and trimethoprim combination is an antibiotic that is often used to treat urinary or intestinal tract infections. This drug can also be used to treat pneumocystis carinii pneumonia (PCP). Pneumocystis carinii pneumonia is seen most commonly in patients whose immune systems are compromised, such as cancer patients, patients with acquired immune deficiency syndrome (AIDS), and transplant patients.

There is a wide range of prescription and non-prescription drugs that should not be used while you are receiving treatment with sulfamethoxazole and trimethoprim combination, because unwanted interactions may occur. There are also a number of medical conditions that could be exacerbated by the use of this drug. Always tell your doctor if you are currently taking any medication and make sure that your treating physician is fully aware of your medical history.

Sulfamethoxazole and trimethoprim combination is a highly effective antibiotic treatment. However, you must always make the effort to communicate with your doctor or health care provider during the course of your treatment. This medication should clear up your infection and prevent it from recurring, but in order to achieve the best results, it is important that you complete your full course of treatment.

Last Reviewed:
December 23, 2017
Last Updated:
April 03, 2018