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Primsol Side Effects

Generic Name: trimethoprim

Note: This page contains side effects data for the generic drug trimethoprim. It is possible that some of the dosage forms included below may not apply to the brand name Primsol.

For the Consumer

Applies to trimethoprim: oral solution, oral tablet

As well as its needed effects, trimethoprim (the active ingredient contained in Primsol) may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking trimethoprim, check with your doctor immediately:

Less common:
  • Skin rash or itching
  • Black, tarry stools
  • blood in urine or stools
  • bluish fingernails, lips, or skin
  • changes in facial skin color
  • chills
  • difficult breathing or shortness of breath
  • fever with or without chills
  • general feeling of discomfort or illness
  • headache
  • joint or muscle pain
  • nausea
  • neck stiffness
  • pale skin
  • pinpoint red spots on skin
  • redness, blistering, burning, tenderness, peeling, or loosening of skin or mucous membranes
  • redness, swelling, or soreness of tongue
  • red skin lesions, often with a purple center
  • sore throat
  • swelling
  • thickened or scaly skin
  • unusual bleeding or bruising
  • unusual tiredness or weakness

Minor Side Effects

Some trimethoprim side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

Less common:
  • Diarrhea
  • loss of appetite
  • nausea or vomiting
  • stomach cramps or pain

For Healthcare Professionals

Applies to trimethoprim: compounding powder, oral solution, oral tablet


The incidence of rash was 2.9% to 6.7% at recommended doses of 200 mg/day.

A higher incidence of rash was reported in clinical trials using large doses of trimethoprim (the active ingredient contained in Primsol) These rashes had an onset of 7 to 14 days after begin of therapy and were maculopapular, morbilliform, pruritic, and mild to moderate in severity.

One case report described Stevens-Johnson syndrome, arthritis, and uveitis associated with trimethoprim.[Ref]

Common (1% to 10%): Rash (up to 6.7%)
Rare (less than 0.1%): Stevens-Johnson syndrome, exfoliative dermatitis, erythema multiforme, toxic epidermal necrolysis (Lyell syndrome)
Frequency not reported: Pruritus, phototoxic skin eruptions[Ref]


Common (1% to 10%): Diffuse, often pruritic, maculopapular or urticarial rashes (up to 7%)
Rare (less than 0.1%): Anaphylaxis, diffuse pneumonitis
Frequency not reported: Fixed drug eruption, linear fixed drug eruption[Ref]

A Dutch retrospective analysis identified 13 cases of probable or possible anaphylaxis with a probable or definite causal relationship to trimethoprim.[Ref]


Rare cases of Clostridium difficile pseudomembranous colitis have been reported during or after trimethoprim (the active ingredient contained in Primsol) therapy.

Frequency not reported: Epigastric distress, nausea, vomiting, glossitis, Clostridium difficile associated diarrhea, mild abdominal distress, pseudomembranous colitis


Since trimethoprim (the active ingredient contained in Primsol) inhibits a step of folate synthesis in vivo, megaloblastic anemia was more likely in patients with folate deficiency, such as alcoholics, the malnourished, and in patients with chronic hemolytic anemia.[Ref]

Frequency not reported: Leukopenia, megaloblastic anemia, methemoglobinemia, neutropenia, thrombocytopenia[Ref]


Frequency not reported: Hyperkalemia, hyponatremia[Ref]


Trimethoprim may inhibit renal tubular creatinine secretion, resulting in increased serum levels. Some data indicated a significant decrease in creatinine clearance associated with trimethoprim (the active ingredient contained in Primsol) These changes appeared to be completely reversible upon discontinuation of therapy.

Trimethoprim acts like amiloride and blocks apical membrane sodium channels in the distal nephron. This resulted in inhibition of potassium secretion and mild hyperkalemia in some cases. Up to 20% of patients with AIDS who were given trimethoprim-sulfamethoxazole developed mild hyperkalemia due to the effect of trimethoprim, not sulfamethoxazole, on the kidney.[Ref]

Frequency not reported: Increased BUN, increased serum creatinine levels, renal tubular creatinine secretion inhibited, decreased creatinine clearance, aldosterone-antagonistic effect in the renal tubule[Ref]

Nervous system

Trimethoprim-induced aseptic meningitis was characterized by a sterile cerebral spinal fluid pleocytosis (usually lymphocytic) associated with meningismus. Trimethoprim-associated aseptic meningitis, like that associated with some nonsteroidal anti-inflammatory medications, may be more likely in patients with underlying connective tissue diseases, such as systemic lupus erythematosus or Sjogren's syndrome. Occult bacterial, viral, and atypical etiologies of meningitis must also be considered. Cases of aseptic meningitis have been reported in AIDS patients.[Ref]

Rare (less than 0.1%): Aseptic meningitis[Ref]


Rare (less than 0.1%): Cholestatic jaundice
Frequency not reported: Elevated serum transaminases, elevated bilirubin[Ref]


Frequency not reported: Fever


One case report described Stevens-Johnson syndrome, arthritis, and uveitis associated with trimethoprim (the active ingredient contained in Primsol) [Ref]

Rare (less than 0.1%): Arthritis (at least 1 case)[Ref]


One case report described Stevens-Johnson syndrome, arthritis, and uveitis associated with trimethoprim (the active ingredient contained in Primsol) [Ref]

Rare (less than 0.1%): Uveitis (at least 1 case)[Ref]


1. Arola O, Peltonen R, Rossi T "Arthritis, uveitis, and Stevens-Johnson syndrome induced by trimethoprim." Lancet 351 (1998): 1102

2. Gibson J "Recurrent trimethoprim-associated fixed skin eruption." Br Med J 284 (1982): 1529-30

3. Kanwar A, Bharija S, Singh M, Belhaj M "Fixed drug eruption to trimethoprim." Dermatologica 172 (1986): 230-1

4. Wanat KA, Anadkat MJ, Klekotka PA "Seasonal variation of Stevens-Johnson syndrome and toxic epidermal necrolysis associated with trimethoprim-sulfamethoxazole." J Am Acad Dermatol 60 (2009): 589-94

5. Nwokolo C, Byrne L, Misch K "Toxic epidermal necrolysis occurring during treatment with trimethoprim alone." Br Med J 296 (1988): 970

6. Chandler M "Recurrence of phototoxic skin eruption due to trimethoprim." J Infect Dis 153 (1986): 1001

7. Higgins T, Niklasson P "Hypersensitivity pneumonitis induced by trimethoprim." Br Med J 300 (1990): 1344

8. OzkayaBayazit E, Baykal C "Trimethoprim-induced linear fixed drug eruption." Br J Dermatol 137 (1997): 1028-9

9. Bijl AMH, VanderKlauw MM, VanVliet ACM, Stricker BHC "Anaphylactic reactions associated with trimethoprim." Clin Exp Allergy 28 (1998): 510-2

10. Alonso MD, Marcos C, Davila I, et al "Hypersensitivity to trimethoprim." Allergy 47 (1992): 340-2

11. OzkayaBayazit E, Gungor H "Trimethoprim-induced fixed drug eruption: positive topical provocation on previously involved and uninvolved skin." Contact Dermatitis 39 (1998): 87-8

12. "Product Information. Trimpex (trimethoprim)." Roche Laboratories, Nutley, NJ.

13. Hughes BR, Holt PJ, Marks R "Trimethoprim associated fixed drug eruption." Br J Dermatol 116 (1987): 241-2

14. Hedlund J, Aurelius E, Andersson J "Recurrent encephalitis due to trimethoprim intake." Scand J Infect Dis 22 (1990): 109-12

15. Chan M, Beale D, Moorhead J "Acute megaloblastosis due to cotrimoxazole." Br J Clin Pract 34 (1980): 87-8

16. Sheehan J "Trimethoprim-associated marrow toxicity." Lancet 2 (1981): 692

17. Choi MJ, Fernandez PC, Patnaik A, Coupaye-Gerard B, D'Andrea D, Szerlip H, Kleyman TR "Brief report: trimethoprim-induced hyperkalemia in a patient with AIDS." N Engl J Med 328 (1993): 703-6

18. Perlmutter EP, Sweeney D, Herskovits G, Kleiner M "Severe hyperkalemia in a geriatric patient receiving standard doses of trimethoprim-sulfamethoxazole." Am J Med Sci 311 (1996): 84-5

19. Smith GW, Cohen SB "Hyperkalaemia and non-oliguric renal failure associated with trimethoprim." Br Med J 308 (1994): 454

20. Alappan R, Perazella MA, Buller GK "Hyperkalemia in hospitalized patients treated with trimethoprim-sulfamethoxazole." Ann Intern Med 124 (1996): 316-20

21. Greenberg S, Reiser IW, Chou SY "Hyperkalemia with high-dose trimethoprim-sulfamethoxazole therapy." Am J Kidney Dis 22 (1993): 603-6

22. Schlanger LE, Kleyman TR, Ling BN "K+-sparing diuretic actions of trimethoprim - inhibition of na+ channels in a6 distal nephron cells." Kidney Int 45 (1994): 1070-6

23. Kastrup J, Petersen P, Bartram R, Hansen JM "The effect of trimethoprim on serum creatinine." Br J Urol 57 (1985): 265-8

24. Myre S, McCann J, First M, Cluxton R "Effect of trimethoprim on serum creatinine in healthy and chronic renal failure volunteers." Ther Drug Monit 9 (1987): 161-5

25. Gabriels G, Stockem E, Greven J "Potassium-sparing renal effects of trimethoprim and structural analogues." Nephron 86 (2000): 70-8

26. Berg K, Nordby G, Rootwelt K, et al "Effects on renal function of combined treatment with trimethoprim and cyclosporine A in kidney transplant patients." Transplant Proc 20 (1988): 413-5

27. Myre SA, McCann J, First MR, Cluxton RJ "Effect of trimethoprim on serum creatinine in healthy and chronic renal failure volunteers." Ther Drug Monit 9 (1987): 161-5

28. McCue J, Zandt J "Acute psychoses associated with the use of ciprofloxacin and trimethoprim-sulfamethoxazole." Am J Med 90 (1991): 528-9

29. Carlson J, Wiholm BE "Trimethoprim associated aseptic meningitis." Scand J Infect Dis 19 (1987): 687-91

30. Pashankar D, Mcardle M, Robinson A "Co-trimoxazole induced aseptic meningitis." Arch Dis Child 73 (1995): 257-8

31. Derbes SJ "Trimethoprim-induced aseptic meningitis." JAMA 252 (1984): 2865-6

32. Jurado R, Carpenter SL, Rimland D "Trimethoprim-sulfamethoxarole-induced meningitis in patients with HIV infection." Am J Med Sci 312 (1996): 27-9

33. Harrison MS, Simonte SJ, Kauffman CA "Trimethoprim-induced aseptic meningitis in a patient with AIDS: case report and review." Clin Infect Dis 19 (1994): 431-4

34. Tanner A "Hepatic cholestasis induced by trimethoprim." Br Med J 293 (1986): 1072-3

35. Kowdley K, Keeffe E, Fawaz K "Prolonged cholestasis due to trimethoprim-sulfamethoxazole." Gastroenterology 102 (1992): 2148-50

It is possible that some side effects of Primsol may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.