Sulfamethoxazole and Trimethoprim - Uses, Dosage, Side Effects, Drug Warnings, and Precautions

Overview:

Sulfamethoxazole and Trimethoprim are fixed combination drugs used to treat several bacterial infections, including lung infections, bacterial meningitis, skin infections, sinusitis, urinary tract infections, traveler’s diarrhea, and certain types of pneumonia. Sulfamethoxazole and Trimethoprim are available as oral tablets, suspensions (liquids), and injections (which can only be administered by a healthcare professional). This medication stops the growth of bacteria and is employed in specific types of bacterial infections only. Do not take this drug if there is a history of allergy or hypersensitivity to Sulfamethoxazole, Trimethoprim, or any other doses of the medication. In case of skin rash or any other unusual symptoms while using the medicine, report to the doctor immediately.

Drug Group:

Sulfamethoxazole and Trimethoprim come under the broad class of antimicrobials. The combination is commonly referred to as Co-trimoxazole. Sulfamethoxazole belongs to the class of antibiotics called the Sulfonamides, and Trimethoprim comes under folic acid inhibitors. The medicines in this group are primarily against specific bacterial infections.

What Is Sulfamethoxazole and Trimethoprim Combination For?

This drug combination is used to treat the following bacterial infections:

• Sinusitis (inflammation of the sinus).

• Bacterial meningitis (inflammation of the meninges-membrane covering the brain and spinal cord).

• Urinary tract infections.

• Shigellosis (infection caused by Shigella bacteria).

• Skin infections.

• Osteomyelitis (inflammation of the bone by bacteria).

• Bacteremia (bacteria in the blood).

• Traveler’s diarrhea.

Sulfamethoxazole, Trimethoprim, or any antibiotic, will not work for infections (cold, flu) caused by viruses. Never take Sulfamethoxazole Trimethoprim or any other medicine without consulting the doctor first.

How Does Sulfamethoxazole and Trimethoprim Combination Work?

Sulfamethoxazole and Trimethoprim are a combination of two antibiotics with different mechanisms of action, and the net effect has an additive or synergistic effect against bacteria. The mechanism of action is as follows:

• Sulfamethoxazole is a sulfonamide. The action of this class is inhibiting the bacterial synthesis of dihydrofolic acid. Now, dihydrofolate is an essential dose in synthesizing nucleic acids. Nucleic acids make up the genetic material of the bacteria and hence are vital for its survival.

• Trimethoprim, in a similar manner, inhibits the synthesis of tetrahydrofolic acid, which is again synthesized from dihydrofolic acid.

Hence, both the antibiotics in this combination prevent the subsequent steps of nucleic acid synthesis and thereby kill the bacteria.

The Onset of Action:

About 97% (Sulfamethoxazole) and 90% (Trimethoprim) of the drug reach the blood circulation. The drug reaches its maximum concentration in blood in one to four hours post-oral administration. It is excreted mainly through the kidneys, and around 85% of Sulfamethoxazole and 66 % of Trimethoprim is excreted through urine.

In short, the onset of action for this medication is between one to four hours after oral administration. And the action may last as long as 6 to 12 hours.

Habit-Forming:

There have been no reports of habit-forming tendencies in people taking this drug.

Expiry Date:

Do not continue the use of this medicine after it expires. The expiry date will be provided on the back of the drug packet.

What Is the Dosage of Sulfamethoxazole and Trimethoprim Drug Combination?

The dosing will depend on the type and severity of the infection. The doctor may adjust the dose and duration based on the response and if you are experiencing any side effects.

Sulfamethoxazole and Trimethoprim are available in the following doses and dosage forms:

• Oral Tablet: (Sulfamethoxazole and Trimethoprim) 400 mg-80 mg, 800 mg-160 mg.

• Oral Suspension: (Sulfamethoxazole and Trimethoprim) 200 mg/5 ml-40 mg/5 ml.

• Injection: (Sulfamethoxazole and Trimethoprim) 80 mg/1 ml-16 mg/1 ml.

It is also used for specific bacterial infections in HIV (human immunodeficiency virus) patients. The dosing will be as directed by the physician.

In the case of children, women, and patients with kidney and liver disease, the doctor will adjust the dosage.

How to Use Sulfamethoxazole and Trimethoprim Combination?

Tablet:

Swallow the tablet as a whole with a glass of water.

Suspension:

Before each dose, thoroughly shake this medication. Utilize a measuring tool or spoon to precisely measure the dosage. As directed by the doctor, take this medication by mouth with a full glass of water.

• Take it with food or milk in case of stomach trouble.

• Unless the doctor instructs, stay hydrated while taking this medication to reduce the minor risk of developing kidney stones.

• Take this antibiotic at regular intervals. Administer the medication at the same time(s) every day to make it easier to remember.

• Even if symptoms go away after a few days, keep taking this medication until the entire advised dosage is gone. If it is stopped too soon, the bacteria might be able to continue to thrive and cause an infection to recur.

Missed Dose:

While on therapy on this drug, take it as soon as the patient remembers if a dose is missed. However, if it is already time for the next dose, avoid double dosing, as it might result in severe adverse reactions. Just skip the missed dose and take the next dosage.

Overdose:

In case the medication is taken, then the prescribed amount and unusual symptoms arise, contact the emergency department or the nearest poison control center immediately.

What Are the Contraindications of Sulfamethoxazole and Trimethoprim Combination?

The use of the Sulfamethoxazole and Trimethoprim combination is strictly unadvised under the following conditions:

• Previous allergy to the drug or its doses.

• For infants less than two years of age.

• Liver damage.

• Kidney insufficiency.

• While on therapy with the drug Dofetilide.

What Are the Drug Warnings and Precautions?

Let the doctor know if any of the following conditions are present:

1. Allergies: Any history of allergy to any of the doses of the medication. Avoid use in such cases.

2. Folic Acid Deficiency: The drug may reduce folic acid levels. Therefore, notify the doctor if there is a history of folic acid deficiency.

3. Kidney Disease: Dose adjustment may be required. Alert the doctor in case of any kidney diseases.

4. Liver Diseases: Avoid use in case of significant liver diseases.

5. Blood Disorders: Inform the doctor there is a history of porphyria (blood disorder).

6. High Potassium Levels: May elevate potassium levels. Inform the healthcare provider if the potassium levels are high.

7. Low Sodium Levels: Inform the doctor that this drug may reduce sodium levels.

8. Sun Exposure: The patient can become more sun-sensitive due to this treatment. Keep sun exposure to a minimum. Avoid using sunlamps and tanning booths. When outdoors, wear protective gear and sunscreen. If the patient experiences skin blisters or redness, seek medical attention immediately.

9. Diabetes: The blood sugar may be impacted by this product. As advised, check the blood sugar frequently, and inform the doctor of the results. Call the doctor immediately if the patient experiences low blood sugar symptoms.

10. Older Population: The adverse effects of this medication, particularly skin responses, blood problems, easy bleeding or bruising, and high potassium blood levels, may be more noticeable in older persons. The doctor will make the necessary adjustments.

11. Pregnancy: The drug might be harmful to the fetus. If the patient is pregnant or intends to get pregnant, let the doctor know for necessary intervention.

12. Breastfeeding: This medication enters breast milk. Therefore, if breastfeeding, speak with the doctor.

What Are the Side Effects of Sulfamethoxazole and Trimethoprim Combination?

The common side effects include:

• If the patient experiences symptoms of an allergic reaction or a severe skin reaction, seek emergency medical attention right once (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

• Sensitivity to light.

• Severe abdominal pain and bloody or watery diarrhea (even if it happens months after the previous dose).

• Fever.

• Breathing difficulty.

• Nausea or vomiting.

• Yellowing of skin or eyes.

• Joint pain.

• Seizures.

• Change in urine color.

• High Potassium: Seek medical help if the patient experiences nausea, weakness, tingling, chest pain, irregular heartbeats, and loss of movement, or if the patient has a history, inform the doctor immediately.

• Low Sodium Levels: Symptoms include shakiness, dizziness, and loss of consciousness. Get medical help immediately.

Seek medical help if the patient experiences these symptoms if they become severe or do not go away.

What Are the Interactions of Sulfamethoxazole and Trimethoprim Drug Combination?

Drugs normally have interactions with other drugs, food, and supplements. These may lead to unwanted reactions. Some of the interactions of the drug are as follows:

1. With Other Drugs:

• Acenocoumarol.

• Amiloride.

• Amiodarone.

• Amitriptyline.

• Benazepril.

• Bretylium.

• Candesartan Cilexetil.

• Captopril.

• Ceritinib.

• Chloral Hydrate.

• Chloroquine.

• Chlorpromazine.

• Cholera Vaccine, Live.

• Clarithromycin.

• Digoxin.

• Disopyramide.

• Enalapril.

• Erythromycin.

• Flecainide.

• Fluconazole.

• Fluoxetine.

• Foscarnet.

• Fosinopril.

• Gemifloxacin.

• Ibutilide.

• Imipramine.

• Leucovorin.

• Lidoflazine.

• Lisinopril.

• Losartan.

• Mefloquine.

• Octreotide.

• Olmesartan Medoxomil.

• Probucol.

• Quinapril.

• Quinidine.

• Ramipril.

• Risperidone.

• Sotalol.

• Spiramycin.

• Spironolactone.

• Telmisartan.

• Valsartan.

• Warfarin.

• Zofenopril.

• Zotepine.

This list does not include all the interacting drugs with Sulfamethoxazole and Trimethoprim. Consult the doctor or pharmacist to check for interactions with the patient's medications.

2. With Alcohol: Avoid drinking alcohol to avoid unpleasant side effects like rapid heartbeat, warmth or redness under the skin, tingling, nausea, and vomiting.

3. With Food: Do not consume anything that contains propylene glycol as its ingredient, as it may cause serious interaction. It is a common component in processed foods and beverages.

What Are the Common Brands or Trade Names of the Sulfamethoxazole and Trimethoprim Combination?

• Tablet Antrima (800mg/160mg).

• Tablet Bactrim (100mg/20mg).

• Suspension Bactrim (200mg/40mg/5mL).

• Septran (200mg/40mg/5mL).

• Tablet Septran (100mg/20mg).