Sulfamethoxazole/Trimethoprim – Oral

As an antibiotic, oral sulfamethoxazole/trimethoprim is used to treat a wide range of bacterial infections including bronchitis, middle ear infections and more.

Overview

Oral sulfamethoxazole/trimethoprim is prescribed to patients suffering from one or more of a wide range of illnesses caused by bacterial infections. These include bronchitis, shigellosis (also known as bacillary dysentery), middle ear infections (also known as otitis media), urinary tract infections and traveler's diarrhea. It is also designed to treat (and, furthermore, prevent) certain types of pneumonia, including pneumocystis carinii pneumonia (also known as PCP) or pneumocystis jiroveci pneumonia.

The medication works by targeting the cause of your condition, which is the bacteria behind the infection. You should be aware that oral sulfamethoxazole/trimethoprim will not work on viral infections, and this includes influenza (flu) and the common cold.

This antibiotic is only available with a prescription from your physician, and it comes in either tablet or suspension format. This medication is known by a wide range of brand names, and you may see it referred to in this way in the store, the pharmacy or online. In the USA, these are Sulfatrim Pediatric, Bactrim, SMZ-TMP Pediatric, Septra DS, Bactrim DS, Septra, and Sulfatrim. In Canada, it is known as Novo-Trimel, Nu-Cotrimox, Septa Pediatric, Apo-Sulfatrim and Septra Pediatric Suspension.

Conditions Treated

  • Bronchitis
  • Shigellosis (also known as bacillary dysentery)
  • Urinary tract infections
  • Traveler's diarrhea
  • Middle ear infections (also known as otitis media)
  • Pneumocystis jiroveci pneumonia
  • Pneumocystis carinii pneumonia

Type of Medicine

  • Antibiotic

Side Effects

As with most medications, taking oral sulfamethoxazole/trimethoprim can cause unpleasant and unwanted side effects in addition to relief from your symptoms.

Generally, the side effects that can potentially occur as a result of taking oral sulfamethoxazole/trimethoprim can be split into two categories.

The first category of side effects includes those which are more serious in nature, and which need to be dealt with by a doctor straight away.

In the event that you experience any of these symptoms, you should not panic but should get in touch with your doctor as soon as possible. If they are not available, you should consult another medical professional. You or someone with you should inform this person that you are currently taking oral sulfamethoxazole/trimethoprim.

Serious side effects related to digestion and excretion-related problems include the following symptoms:

  • Black stools
  • Pain in the stomach or abdomen
  • Dark urine
  • Diarrhea
  • Vomiting of blood
  • Difficulty passing urine

Serious symptoms related to throat and breathing functions:

  • Pronounced cough or hoarseness
  • Sore throat
  • Extended shortness of breath
  • Tightness in the chest

Rare but serious side effects that are skin-related:

  • Sudden peeling or loosening of the skin
  • Emergence of blisters
  • Changes to your skin's hue
  • Feeling of chills running down your skin
  • Itchiness
  • Pale skin
  • Rashes
  • Lesions with a purple center

General rare side effects that may require attention from a doctor:

  • Feeling of weakness or fatigue
  • Headache
  • Pain in the muscles or lower back
  • Swelling of the foot
  • Bad breath

In addition to these rare side effects, there are more serious side effects with incidences which are not currently known. In the event that you experience any of these, you should consult your doctor immediately.

These side effects include a range of pains throughout the body, including in your back, legs and stomach, tenderness around your abdomen, pain in your chest, and more.

Urine-related side effects:

  • Blood in the urine (or in the stools)
  • Cloudy urine
  • Decrease in the amount of urine produced or the number of times you need to pass it
  • Pain while passing urine or the inability to pass it whatsoever.

General serious side effects:

  • Hair loss
  • Hearing loss
  • Sudden increase in thirst
  • Feeling of indigestion
  • Irregular heartbeat
  • Eye redness around the part that is usually white
  • Unusual or unplanned gain or loss of weight
  • Weakness in parts of the body such as the feet, hands or legs

Miscellaneous side effects:

  • Bleeding gums
  • Changes to vision or even blindness
  • Bloating
  • Unusual blue tinge to your nails or lips
  • Convulsions
  • Feelings of confusion
  • Ringing in the ears.

In addition, a range of skin-related problems - such as pins and needles, a tingling sensation, itchiness, blue patches or red pinpoints on your skin or numbness - are all included in the serious category. In the event that you experience any of these side effects, you should consult your physician right away.

Some side effects which you may experience as a result of taking oral sulfamethoxazole/trimethoprim are less serious and do not ordinarily require medical attention.

Usually, you do not need to consult your doctor if you experience any of these side effects, as they are simply the body's natural response to the drugs you are taking and often will go away on their own accord within a few days. The only circumstances in which you need to consult your doctor if you experience these side effects is if they are persistent and do not go away, or if they are causing you lots of problems.

A common, less serious side effect of taking oral sulfamethoxazole/trimethoprim is the passing of gas. The incidences of other less serious side effects of this medication are not currently known. This category, however, includes a wide range of mental health problems such as feelings of sadness, increased irritability, inability to feel emotions, loss of interest in activities previously enjoyed, hallucinations or hearing things which are not actually real, and nervousness.

In addition, you may experience other general side effects such as redness of the skin, a spinning sensation, increased sensitivity to light and to the sun, difficulty concentrating or falling asleep, or a feeling of disorientation or that you or your surroundings are moving. Again, you only need to go to your physician if these side effects persist or if they are causing you extensive problems.

Remember, not all patients experience the same side effects. Experiences taking oral sulfamethoxazole/trimethoprim can and do vary from patient to patient, so there is no guarantee that you will or will not experience a particular side effect.

These lists of potential side effects are not exhaustive, and you should always consult the full list of possible side effects which should come inside the packaging of your medication.

If you are concerned about any of the possible side effects or you need some advice on how to mitigate the effects of them, it is a good idea to speak to your physician or healthcare professional. Not only will they be able to put your mind at rest, they will hopefully also be able to offer you some tips on how to manage your symptoms as your course of oral sulfamethoxazole/trimethoprim runs on.

Dosage

When it comes to taking oral sulfamethoxazole/trimethoprim, your physician will always prescribe you a dosage which is bespoke to you and which is designed with your needs in mind. You should always follow these instructions, and you should never change your dosage without the permission of your physician.

In addition to the precise dosage, you should also again never change other aspects of your prescription - such as the frequency of doses, the number of tablets to be taken, the intervals to leave in between, and so on - without the permission of your physician.

However, there are some standard dosages which have been released as guidelines. These differ based on the specific condition which is being treated.

For patients who are taking this medication to treat bacterial infections, the standard dosage also varies based on weight. Those adults and children who weigh over 40 kilograms (kg) are often prescribed 800 milligrams (mg) of sulfamethoxazole and 160 mg of trimethoprim for this condition. Generally, they are asked to take it once every 12 hours for a period of between ten and 14 days.

Children who are aged older than two months and who weigh up to 40 kg will usually have a precise dosage, based on body weight, calculated by their physician. Usually, 40 mg of sulfamethoxazole will be prescribed per kilogram of body weight, and 8 mg per kilogram of body weight of trimethoprim will be prescribed alongside. Ordinarily, this will be given in two doses (divided) at intervals of every 12 hours for a period of 10 days.

For children under two months, this medication is not usually recommended for use.

Those who are taking this medication to treat traveler's diarrhea will need to use it differently.

Often, adults will be prescribed 800 mg of sulfamethoxazole followed by 160 mg of trimethoprim, and they will need to take this at intervals of 12 hours for a period of five days.

For children who are aged two months and older, the relevant dosage will need to be determined by a doctor. It is not recommended that children under the age of two months take this medication.

Patients who are taking this medication to treat (as opposed to prevent) pneumocystis jiroveci pneumonia or pneumocystis carinii pneumonia (PCP) will again take a different level of the drug.

Adults and children who are aged over two months will again have their exact dosage determined by their physician as a result of their body weight. Usually, this will be around 75 to 100 mg per every kilogram of body weight for sulfamethoxazole, while 15 to 20 mg will be prescribed per kilogram of body weight for trimethoprim.

Usually, this will be taken in doses once every six hours for a period of 14 to 21 days, and the doses will be equally divided.

Again, usage of this medication is not recommended for children under the age of two months.

Finally, patients who are taking this medication in order to prevent (as opposed to treat) pneumocystis jiroveci pneumonia or pneumocystis carinii pneumonia (PCP) will have a slightly different treatment regimen to follow.

For adults, 800 mg of sulfamethoxazole will need to be taken alongside 160 mg of trimethoprim, and this will need to happen once a day. For children who are aged older than two months, the dose will be based on body size and as a result will need to be decided by a physician.

Usually, 750 mg of sulfamethoxazole will be prescribed per day per square meter of body surface, followed by 150 mg of trimethoprim - again per square meter of body surface and per day. Usually, your physician will instruct you to give this to your child in doses divided up equally twice per day for three days in a week, and it will often be stipulated that this needs to happen on consecutive days. For example, your child may be required to take the medication on Thursday, Friday and Saturday. Often, the total dose will be capped at around 1600 mg of sulfamethoxazole and 320 mg of trimethoprim per day.

Once again, use of this medication is not recommended for children under the age of two months.

Interactions

As with many other drugs, oral sulfamethoxazole/trimethoprim can interact with a wide range of other drugs once inside your body.

There are many drugs which interact with oral sulfamethoxazole/trimethoprim, and for that reason, you should always provide your physician with an up to date list of the medications you currently take. This is essential, as your physician may opt to alter the current configuration of your medication depending on what other drugs you take.

Firstly, if you are currently taking any drugs which thin the blood, you should tell your physician. These include warfarin, as well drugs such as methenamine.

In addition, you should bear in mind that antibiotics do in some cases interact with hormonal birth control and can cause a drop in their effectiveness. Speak to your physician if you rely on a hormonal form of birth control, as you may need to take other precautions to prevent getting pregnant.

There are lots of medications which may interact with this drug, and they can broadly be split into three categories. The first category of drug which can interact with this medication contains those which can cause serious interactions. This category includes drugs such as Singulair (montelukast), Azor (amlodipine/olmesartan), cyclosporine, Glu-K (potassium chloride), K-Effervescent (potassium bicarbonate) and Micardis HCT (hydrochlorothiazide/telmisartan).

Secondly, some drugs can cause moderate level interactions with this medication. These include ProAir HFA (albuterol), Azithromycin Dose Pack (azithromycin), Afrezza (rapid-acting insulin inhalation), Tri-Norinyl (ethinyl estradiol/norethindrone) and Triquilar 28 (ethinyl estradiol/levonorgestrel).

Finally, there are also some medications which can cause only low-level interactions with this medication. Again, some of these are over the counter medications which can be bought in stores and pharmacies without a prescription from a medical professional, so you should always alert your physician to the full list of drugs you are taking - even those which you bought over the counter.

Drugs in this category include Synthroid (levothyroxine), Zyrtec (cetirizine) and Xanax (alprazolam). Tylenol (acetaminophen) is also included here. A number of vitamins are also included, such as Vitamin C (ascorbic acid), Vitamin B12 (cyanocobalamin), Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).

Warnings

When it comes to taking oral sulfamethoxazole/trimethoprim, it's important to bear in mind that there are a number of warnings associated with taking this drug. These will be listed in full in the information booklet which comes with your medication, so you should consult this if you are unsure.

You should be aware that there is a risk that this medication will lower the number of platelets which exist in your blood. Because these are required for your blood to clot properly, bleeding for longer periods or acquiring infections may become more common.

In addition, there is a chance that this medication will cause you to experience severe diarrhea. Although this may seem like an embarrassing problem, it is vital that you speak to your doctor if you plan to take medication to deal with this problem. You are advised to keep an eye on this problem in the long term, too, as it could happen two months or more after you cease to take oral sulfamethoxazole/trimethoprim.

You are also advised that this medication can cause anaphylaxis, a severe allergic reaction. This condition is often signified by problems such as a swollen throat, face or tongue, as well as rashes, itchy areas or chest pain. In the event that you experience any of these symptoms, you should speak to your physician right away, or pay a visit to the emergency room as soon as possible. Once there, you or someone with you should tell the staff on duty that you are taking oral sulfamethoxazole/trimethoprim.

Finally, there is also a possibility that you will experience electrolyte problems as a direct consequence of using this medicine. These issues include high levels of potassium in the bloodstream, known as hyperkalemia, or low levels of sodium in the bloodstream, known as hyponatremia. These conditions may be indicated by symptoms such as weakness, confusion, an irregular heartbeat, difficulty breathing, or extended muscle twitching. Again, if you happen to experience any of these symptoms while taking this medication, you should consult your physician right away - and if that is not possible, you should attend the nearest emergency room as soon as possible. Once you arrive, you or someone with you should tell the staff on duty that you are taking oral sulfamethoxazole/trimethoprim.

Remember, this list of warnings is not exhaustive. You should speak to your physician or other healthcare professionals if you have any concerns, as they will be able to put your mind at ease.

Storage

When it comes to storing your oral sulfamethoxazole/trimethoprim, it's vital that you follow some precautions in order to make sure that you do not accidentally damage the drugs before you take them.

Firstly, you should ensure that your oral sulfamethoxazole/trimethoprim is always stored out of the reach of children. This is essential in preventing accidental consumption. If you don't have children living with you at your home, you should still ensure that you keep your medication stored in a location where children cannot reach it. That way, you won't be running a risk if children come to visit you in the future and you don't remember to move your medication. Suitable locations include the top shelves of high up kitchen cupboards.

Secondly, you should keep your oral sulfamethoxazole/trimethoprim in an environment which does not damage the medication. This means storing it out of the line of direct light sources such as sunlight, while also making sure that your medication is not stored in an area where it would be exposed to heat, moisture or other adverse environmental conditions. You should never freeze your oral sulfamethoxazole/trimethoprim, as this can damage the medication and prevent it from working at its full capacity.

Although you should never stop using your medication unless a physician advises you to, it's vital that you dispose of any excess oral sulfamethoxazole/trimethoprim in the correct way once you've finished using it. This prevents your medication falling into the wrong hands. If you're not sure how to go about doing this, you should speak to your physician or healthcare professional.

Summary

This medication is designed to treat a range of bacterial infections, including bronchitis, shigellosis (also known as bacillary dysentery), traveler's diarrhea and more. It works by tackling the bacteria causing the infection. This medication does not work for viral infections, such as the flu.

This antibiotic is only available via a prescription from your physician and has a large number of brand names in North America.

As with many drugs, there are some possible side effects as a result of taking this medication. These include serious side effects such as dark stools, pain in the stomach, difficulty passing urine and more. In the event that you experience any of these symptoms, you should not panic but should get in touch with your doctor straight away. If they are not available, you should consult another medical professional.

Your dosage will be determined by your doctor, and you should always follow their advice on dosage as well as other key elements of your medication's course such as the frequency of doses, the intervals necessary between each dose, and more. Standard dosages exist as guidelines only. For children under two months, this medication is not usually recommended for use. Your use of this medication is likely to vary based on what condition you are suffering from.

This medication can interact with a number of other drugs once inside your body. For that reason, you should always ensure your physician has an up to date list of all the medications you are currently taking to prevent any problems further down the line.

This medication comes with a wide range of warnings, and they are often located in the advice booklet which comes along with your medication. You should retain this booklet and ensure you familiarise yourself with the possible problems this medication can cause. If you have any questions, you should speak to a medical professional as soon as possible to put your mind at ease.

It is important to store your medication correctly to prevent it from falling into the wrong hands or creating a safety risk. This means storing it high up out of the reach of children, even if you do not have children living in your house. In addition, you should also ensure you store your medication in good environmental conditions, away from direct light, heat, moisture and more. Do not freeze this medication, and always ensure you dispose of your medication in an appropriate fashion. If you're unsure how to go about doing this, consult your physician or other healthcare professional.

 

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Last Reviewed:
January 30, 2018
Last Updated:
January 27, 2018
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