Co-trimoxazole

Co-trimoxazole MODE OF ACTION

Co-trimoxazole is generally bactericidal; it acts by sequential blockade of folic acid enzymes in the synthesis pathway. The sulfamethoxazole component inhibits formation of dihydrofolic acid from para-aminobenzoic (PABA), whereas trimethoprim inhibits dihydrofolate reductase.


Brands of CO-trimoxazole in Kenya

Alprim, Elys
Bactrim, Roche
Biotrim, Biodeal
Ciplin, Cipla
Cosatrim, Cosmos
Cotreich, GSK
Cotrimoxazole, Flamingo
Cotri, Elys
Diuride, Global
Gestrim, Gesto
Lecotrim, Lab and Allied
Maxotrim, Mac’s
Metrim, Medipharm
Osstrim, Oss-Chemie
Septrimed, Medivet
Septrin, GSK
Shetrim, Shelys
Sulfran, Universal
Sulprim, Sphinx
Trimoprim DS, Medreich
Trimoxol, Dawa
Trizole, PMC
Unitrim, Regal pharmaceuticals
Vircot, Virchow

PHARMACOKINETICS

Cotrimoxazole is rapidly and well absorbed from the gastrointestinal tract and peak plasma concentration reached between 1-4 hours after oral dose.
When orally administered the plasma concentration of Trimethoprim and Sulfamethoxazole are generally around the optimal ratio 0f 1:20
About 50% Co-trimoxazole is excreted in urine in 24 hours

INDICATIONS:

Urinary Tract Infections
For the treatment of urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis and Proteus vulgaris. It is recommended that initial episodes of uncomplicated urinary tract infections be treated with a single effective antibacterial agent rather than the combination.
Acute Otitis Media
For the treatment of acute otitis media in pediatric patients due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae when in the judgment of the physician sulfamethoxazole and trimethoprim offers some advantage over the use of other antimicrobial agents. To date, there are limited data on the safety of repeated use of sulfamethoxazole and trimethoprim oral suspension, USP in pediatric patients under two years of age. Sulfamethoxazole and trimethoprim oral suspension, USP is not indicated for prophylactic or prolonged administration in otitis media at any age.
Acute Exacerbations of Chronic Bronchitis in Adults
For the treatment of acute exacerbations of chronic bronchitis due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae when a physician deems that sulfamethoxazole and trimethoprim , could offer some advantage over the use of a single antimicrobial agent.
Shigellosis
For the treatment of enteritis caused by susceptible strains of Shigella flexneri and Shigella sonnei when antibacterial therapy is indicated.
Pneumocystis jiroveci Pneumonia
For the treatment of documented Pneumocystis jiroveci pneumonia and for prophylaxis against P. jiroveci pneumonia in individuals who are immunosuppressed and considered to be at an increased risk of developing P. jiroveci pneumonia.
Traveler’s Diarrhea in Adults
For the treatment of traveler’s diarrhea due to susceptible strains of enterotoxigenic E. coli.

CONTRA-INDICATIONS

Sulfamethoxazole and trimethoprim is contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides, in patients with a history of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides, and in patients with documented megaloblastic anemia due to folate deficiency.
Sulfamethoxazole and trimethoprim  is contraindicated in pediatric patients less than 2 months of age.
Sulfamethoxazole and trimethoprim oral suspension is also contraindicated in patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored.

ADVERSE DRUG REACTIONS:

The most common adverse effects are gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (such as rash and urticaria).
Hematologic
Agranulocytosis, aplastic anemia, thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia.
Allergic Reactions
Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylaxis, allergic myocarditis, erythema multiforme, exfoliative dermatitis, angioedema, drug fever, chills, Henoch-Schoenlein purpura, serum sickness-like syndrome, generalized allergic reactions, generalized skin eruptions, photosensitivity, conjunctival and scleral injection, pruritus, urticaria and rash. In addition, periarteritis nodosa and systemic lupus erythematosus have been reported.
Gastrointestinal
Hepatitis (including cholestatic jaundice and hepatic necrosis), elevation of serum transaminase and bilirubin, pseudomembranous enterocolitis, pancreatitis, stomatitis, glossitis, nausea, emesis, abdominal pain, diarrhea, anorexia.
Genitourinary
Renal failure, interstitial nephritis, BUN and serum creatinine elevation, toxic nephrosis with oliguria and anuria, crystalluria and nephrotoxicity in association with cyclosporine.
Metabolic and Nutritional
Hyperkalemia, hyponatremia
Neurologic
Aseptic meningitis, convulsions, peripheral neuritis, ataxia, vertigo, tinnitus, headache.
Psychiatric
Hallucinations, depression, apathy, nervousness.
Endocrine
The sulfonamides bear certain chemical similarities to some goitrogens, diuretics (acetazolamide and the thiazides) and oral hypoglycemic agents. Cross-sensitivity may exist with these agents. Diuresis and hypoglycemia have occurred rarely in patients receiving sulfonamides.
Musculoskeletal
Arthralgia and myalgia. Isolated cases of rhabdomyolysis have been reported with sulfamethoxazole and trimethoprim, mainly in AIDS patients.
Respiratory
Cough, shortness of breath and pulmonary infiltrates
Miscellaneous
Weakness, fatigue, insomnia.
Overdosage:
Treatment should consist of gastric lavage within an hour of ingestion. Increased fluid intake will increase the elimination of sulfamethoxazole. General support measures are recommended.

DRUG INTERACTIONS:

Trimethoprim is an inhibitor of CYP2C8 as well as OCT2 transporter. Sulfamethoxazole is an inhibitor of CYP2C9. Caution is recommended when sulfamethoxazole and trimethoprim is co-administered with drugs that are substrates of CYP2C8 and 2C9 or OCT2.
In elderly patients concurrently receiving certain diuretics, primarily thiazides, an increased incidence of thrombocytopenia with purpura has been reported.
It has been reported that sulfamethoxazole and trimethoprim may prolong the prothrombin time in patients who are receiving the anticoagulant warfarin (a CYP2C9 substrate). This interaction should be kept in mind when sulfamethoxazole and trimethoprim is given to patients already on anticoagulant therapy, and the coagulation time should be reassessed.
Sulfamethoxazole and trimethoprim may inhibit the hepatic metabolism of phenytoin (a CYP2C9 substrate). Sulfamethoxazole and trimethoprim, given at a common clinical dosage, increased the phenytoin half-life by 39% and decreased the phenytoin metabolic clearance rate by 27%. When administering these drugs concurrently, one should be alert for possible excessive phenytoin effect.
Sulfonamides can also displace methotrexate from plasma protein binding sites and can compete with the renal transport of methotrexate, thus increasing free methotrexate concentrations.
There have been reports of marked but reversible nephrotoxicity with coadministration of sulfamethoxazole and trimethoprim and cyclosporine in renal transplant recipients.
Increased digoxin blood levels can occur with concomitant sulfamethoxazole and trimethoprim therapy, especially in elderly patients. Serum digoxin levels should be monitored.
Increased sulfamethoxazole blood levels may occur in patients who are also receiving indomethacin.
Occasional reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses exceeding 25 mg weekly may develop megaloblastic anemia if sulfamethoxazole and trimethoprim is prescribed.
The efficacy of tricyclic antidepressants can decrease when coadministered with sulfamethoxazole and trimethoprim.
Sulfamethoxazole and trimethoprim potentiates the effect of oral hypoglycemics that are metabolized by CYP2C8 (e.g., pioglitazone, repaglinide, and rosiglitazone) or CYP2C9 (e.g., glipizide and glyburide) or eliminated renally via OCT2 (e.g., metformin). Additional monitoring of blood glucose may be warranted.

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References/ Citation:

Sulfamethoxazole and trimethoprim