Trimethoprim

TRIMETHOPRIM

Complete information including dosage, side effects, interactions and pregnancy & breastfeeding warnings for patient and professional use.

Overview and uses

Trimethoprim is an anti bacterial either used as a single drug or in combination with Sulfamethoxazole or sulfadiazine for the treatment of certain type of infections mentioned further in this article along with dosage.

Indication (uses):

Efficacy of Trimethoprim alone can be demonstrated only in below mentioned conditions. For other conditions, best results are obtained when combined with sulfonamides like Sulfamethoxazole or sulfadiazine.

  • Urinary tract infections in adults and children.
  • Prostatitis in adults and children.

For prostatitis, there is no significant advantage of using Trimethoprim in combination with Sulfamethoxazole or sulfadiazine over Trimethoprim alone as these drugs are not concentrated in prostate.

Pharmacological classification: anti bacterial

Brand names: Primsol, Prolomprim, Trimpex.

Dosage form:

  • Available as tablets and oral solution.

Mechanism of action:

Trimethoprim inhibits the formation of bacterial folic acid by inhibiting the formation of tetrahydrofolate by inhibiting dihydrofolate reductase.

Dosage:

  • ADULT DOSE:
    • For urinary tract infections
      • 100 mg orally twice a day (every 12 hours) for 10 days or 200 mg orally once a day for 10 days.
    • For prostatitis
      • 100 mg orally twice a day (every 12 hours) for 10 days or 200 mg orally once a day for 10 days.
    • PEDIATRIC DOSE (based on body weight):
      • 6 mg/kg/day in 2 divided doses.

Renal dose adjustment

  • Creatinine clearance (CrCl) equal to or more than 15 but less than 30 ml/min:
    • Usual dose should be reduced to 50%.
  • Creatinine clearance (CrCl) equal to or more than 15 but less than 30 ml/min:
    • Not recommended for usage in this case.

Hepatic dose adjustments

It is advisable to exercise caution while using Trimethoprim in patients with impaired hepatic functions.

OVERDOSAGE

  • Peritoneal dialysis is not effective.
  • Hemodialysis is moderately effective.
  • Vital signs should be monitored and supportive treatment should be given as and when required.

Side effects or unwanted effects:

  • Occurrence of hypersensitivity or anaphylaxis with Trimethoprim use, though rare but cannot be neglected.
    • Nausea, vomiting, diarrhea, dizziness, abdominal pain, fainting, low blood pressure, rapid heartbeat, tightness of the throat, troubled breathing, hives or urticaria are some of the symptoms.
    • Consult your doctor as soon as possible if you observe any of the above mentioned symptoms. This may require immediate medical attentions and probably discontinuation of the therapy.
  • Occurrence of cholestatic jaundice is also rare with Trimethoprim use.
    • Itchiness, dark stools, pale coloured urine, yellowing of the skin and whites of the eye are some of the symptoms.
    • Consult your doctor as soon as possible if you observe any of the above mentioned symptoms. This may require immediate medical attentions and probably discontinuation of the therapy.
  • Nausea, vomiting, glossitis, sore mouth, abdominal pain and epigastric distress are some of the common side effects observed with Trimethoprim use.
    • Sore and tender tongue, difficulty in speaking, swallowing or chewing, swelling of the tongue and tongue color changes are some of the symptoms of glossitis. Consult your doctor as this may require an antibiotic or steroid.
  • Occurrence of maculopapular, morbilliform and pruritic skin rash is common with Trimethoprim use.
    • Small red spots on skin, fever, headache, nausea and vomiting, measles like rash, difficulty in breathing, severe head or neck pain, swelling of the face or extremities are some of the symptoms.
    • Consult your doctor as soon as possible if you observe any of the above mentioned symptoms along with a skin rash. This may require immediate medical attention.
  • Hypersensitivity reaction including epidermal necrolysis, erythema multiforme, Stevens – Johnson syndrome and photo sensitization.
    • Consult your doctor as soon as possible if you observe skin rash, red or purple colored skin rash, facial swelling, swelling of the tongue, hives on the skin, joint pain, a painful red area on the skin that spreads quickly, peeling of the skin without blistering, fever, shortness of breath during exercise at first and then at night time while lying down, abnormal heart beat, light headedness, sharp or stabbing chest pain and fatigue are some of the symptoms. This may require immediate medical attention and discontinuation of the therapy.

Warnings and precautions

  • Safety and effectiveness of Trimethoprim as a single drug is not established in pediatric patients less than 12 years of age.
  • Safety and effectiveness of Trimethoprim is not established in pediatric patients less than 2 months of age.

Pregnancy

Category C, which means animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Nursing:

  • Trimethoprim is secreted in human breast milk.
  • Caution should be exercised while administering drug to a nursing mother as it may interfere with folic acid metabolism of the infant.
  • Though no severe side effects have been reported, it is advisable to either stop breast feeding or stop Trimethoprim use in nursing mothers.

Interactions

Drug – drug interactions

  • Use of Trimethoprim with angiotensin converting enzyme (ACE) inhibitors like captopril, enalapril, lisinopril, perindopril, fosinopril, trandolapril, ramipril, imidapril, benazepril and quinapril is contraindicated as it may cause or worsen the pre-existing hyperkalemia.
  • Use of Trimethoprim with angiotensin receptor blockers like losartan, candesartan, irbesartan, valsartan, telmisartan and fimasartan is contraindicated as it may cause or worsen the pre-existing hyperkalemia.
  • Use of Trimethoprim with anti fungals like ketoconazole, fluconazole and itraconazole is contraindicated as it may cause or worsen the pre-existing hyperkalemia.
  • Concomitant use of cyclosporine, spironolactone, digoxin, penicillin G, pentamidine, tacrolimus, succinylcholine, heparin, triamterene and amilioride is contraindicated as it may cause or worsen the pre-existing hyperkalemia.
  • Use of Trimethoprim with beta blockers like atenolol, acebutolol, propranolol, sotalol, timolol, pindolol, labetalol, carvedilol, metoprolol, bisoprolol, esmolol, betaxolol, celiprolol and nebivolol is contraindicated as it may cause or worsen the pre-existing hyperkalemia.
  • Use of Trimethoprim or any combination containing Trimethoprim should be done with caution when used with NSAID (non steroidal anti inflammatory diseases) as these drugs are known to cause water and salt retention.
  • Dofetilide use with Trimethoprim is contraindicated as it imposes a potential for severe heart problems.

Drug-food interactions:

  • Trimethoprim can be taken with or without food.
  • Trimethoprim does not interact with alcohol. However, it’s best to avoid consuming alcohol when taking any medicine.

Click here to go to Trimethoprim forums

Note: The sole purpose of every information shared on this article is to bring awareness. Do not use this information as a medical advice or prescription advice or as a tool for the treatment, diagnosis or prevention of the disease.

By |2017-12-20T13:33:19+00:00May 3rd, 2017|medicines|0 Comments

About the Author:

B. Pharm (K.L.E. society's S.V.V. Patil College of Pharmacy, Bengaluru) M. Pharm (Maharishi Arvind Institute of Pharmacy, Jaipur)

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