Co-Trimoxazole tablets are indicated in children (>12 to <18 years old) and adults (>18 years old) for the treatment of the following infections when owing to sensitive organisms (see section 5.1):
• Treatment and prevention of Pneumocystis jirovecii pneumonitis or “PJP”.
• Treatment and prophylaxis of toxoplasmosis.
• Treatment of nocardiosis.
The following infections may be treated with Co -Trimoxazole where there is bacterial evidence of sensitivity to Co -Trimoxazole and good reason to prefer the combination of antibiotics in Co - Trimoxazole to a single antibiotic:
• Acute uncomplicated urinary tract infection.
• Acute otitis media.
• Acute exacerbation of chronic bronchitis.
Consideration should be given to official guidance on the appropriate use of antibacterial agents.

Posology

General Dosage Recommendations

Where dosage is expressed as "tablets" this refers to the adult tablet, i.e. 80 mg Trimethoprim BP and 400 mg Sulfamethoxazole BP. If other formulations are to be used appropriate adjustment should be made.

Standard dosage recommendations for acute infections

Adults (>18 years old) :

Children over 12 years old (>12 to <18 years old):
The standard dosage for children is equivalent to approximately 6 mg trimethoprim and 30 mg sulfamethoxazole per kg body weight per day, given in two equally divided doses. The schedules for children are according to the child's age and provided in the table below:

Age	Tablets
>12 to <18 years old	2 tablets every 12 hours

Treatment should be continued until the patient has been symptom free for two days; the majority will require treatment for at least 5 days. If clinical improvement is not evident after 7 days therapy, the patient should be reassessed.

As an alternative to Standard Dosage for acute uncomplicated lower urinary tract infections, short- term therapy of 1 to 3 days duration has been shown to be effective.

Elderly patients:
See Special Warnings and Precautions for Use (Section 4.4). Unless otherwise specified standard dosage applies.
Impaired hepatic function:
No data are available relating to dosage in patients with impaired hepatic function. Impaired renal function:

Dosage recommendation :

Children (>12 to <18 years old) and adults (>18 years old):

Creatinine Clearance (ml/min)	Recommended Dosage
>30	2 tablets every 12 hours
15 to 30	1 tablets every 12 hours
<15	Not recommended

No information available for children aged 12 years and under with renal failure. See section 5.2 for the pharmacokinetics in the paediatric population with normal renal function of both components of Co-Trimoxazole, TMP and SMZ.

Measurements of plasma concentration of sulfamethoxazole at intervals of 2 to 3 days are recommended in samples obtained 12 hours after administration of Co -Trimoxazo le. If the concentration of total sulfamethoxazole exceeds 150 microgram/ml then treatment should be interrupted until the value falls below 120 microgram/ml.

Pneumocystis jirovecii pneumonitis

Treatment - Children (>12 to <18 years old) and adults (>18 years old):

A higher dosage is recommended, using 20 mg trimethoprim and 100 mg sulfamethoxazole per kg of body weight per day in two or more divided doses for two weeks. The aim is to obtain pea k plasma or serum levels of trimethoprim of greater than or equal to 5 microgram/ml (verified in patients receiving 1 -hour infusions of intravenous Co -Trimoxazole). (See 4.8 Undesirable Effects).

Prevention - Adults (>18 years old):

The following dose sch edules may be used:

160 mg trimethoprim/800 mg sulfamethoxazole daily 7 days per week.
160 mg trimethoprim/800 mg sulfamethoxazole three times per week on alternate days.
320 mg trimethoprim/1600 mg sulfamethoxazole per day in two divided doses three times per week on alternate days.

Prevention - Children (>12 to <18 years old):

The standard dosage for children is equivalent to approximately 6 mg trimethoprim and 30 mg sulfamethoxazole per kg body weight per day, given in two equally divided doses. The following dose schedules may be used for the duration of the period at risk:

Age	Tablets
>12 to <18 years old	2 tablets every 12 hours, seven days per week
>12 to <18 years old	2 tablets every 12 hours, three times per week on alternative days
>12 to <18 years old	2 tablets every 12 hours, three times per week on consecutive days
>12 to <18 years old	4 tablets once a day, three times per week on consecutive days

The daily dose given on a treatment day approximates to 150 mg trimethoprim/m ²/day and 750 mg sulfamethoxazole/m ²/day. The total daily dose should not exceed 320 mg trimethoprim and 1600 mg sulfamethoxazole.

Nocardiosis - Adults (>18 years old):

There is no consensus on the most appropriate dosage. Adult doses of 6 to 8 tablets daily for up to 3 months have been used.

Toxoplasmosis:

There is no consensus on the most appropriate dosage for the treatment or prophylaxis of this condition. The decision should be based on clinical experience. For prophylaxis, however, the dosages suggested for p revention of Pneumocystis jirovecii pneumonitis may be appropriate.

Method of administration : 
Oral.

It may be preferable to take Co -Trimoxazole with some food or drink to minimise the possibility of gastrointestinal disturbances.

• Hypersensitivity to the active substance(s) sulphonamides, trimethoprim, co-trimoxazole or to any of the excipients listed in section 6.1. • Co-Trimoxazole should not be given to patients with severe hepatic parenchymal damage. Contra - indicated in severe renal insufficiency where repeated measurements of the plasma concentration cannot be performed. • Co-trimoxazole should not be given to infants during the first 6 weeks of life. • Co-Trimoxazole should not be given to patients with a history of drug -induced immune thrombocytopenia with use of trimethoprim and/or sulphonamides. • Co-Trimoxazole should not be given to patients with acute porphyria.

Fatalities, although very rare, have occurred due to severe react ions including Stevens -Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anaemia, other blood dyscrasias and hypersensitivity of the respiratory tract.

• Life-threatening cutaneous reactions Stevens -Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported with the use of Co -Trimoxazole.
• Patients should be advised of the signs and symptoms and monitored closely for skin reactions. The highest risk for occurrence of SJS or TEN is within the first weeks of treatment.
• If symptoms or signs of SJS or TEN (e.g. progressive skin rash often with blisters or mucosal lesions) are present, Co -Trimoxazole treatment should be discontinued (see section 4.8).
• The best results in managing SJS and TEN come from early diagnosis and immediate discontinuation of any suspect drug. Early withdrawal is associated with a better prognosis.
• If the patient has developed SJS or TEN with the use of Co-Trimoxazole, Co -Trimoxazole must not be re -started in this patient at any time.
Particular care is always advisable when treating elderly patients because, as a group, they are more susceptible to adverse reactions and more likely to suffer serious effects as a result particularly
when complicating conditions exi st, e.g. impaired kidney and/or liver function and/or concomitant use of other drugs.
For patients with known renal impairment special measures should be adopted (see section 4.2).
An adequate urinary output should be maintained at all times. Evidence of c rystalluria in vivo is rare, although sulphonamide crystals have been noted in cooled urine from treated patients. In patients suffering from malnutrition the risk may be increased.
Regular monthly blood counts are advisable when Co -Trimoxazole is given fo r long periods, or to folate deficient patients or to the elderly; since there exists a possibility of asymptomatic changes in haematological laboratory indices due to lack of available folate. Supplementation with folinic acid may be considered during tre atment but this should be initiated with caution due to possible interference with antimicrobial efficacy (see section 4.5).
In glucose -6-phosphate dehydrogenase (G -6-PD) deficient patients haemolysis may occur.
Co-Trimoxazole should be given with caution to patients with severe atopy or bronchial asthma.
Co-Trimoxazole should not be used in the treatment of streptococcal pharyngitis due to Group A beta -haemolytic streptococci ; eradication of these organisms from the oropharynx is less effective than with penicillin.
Trimethoprim has been noted to impair phenylalanine metabolism but this is of no significance in phenylketonuric patients on appropriate dietary restriction.
The administration of Co -Trimoxazole to patients known or suspected to be at risk of po rphyria should be avoided. Both trimethoprim and sulphonamides (although not specifically sulfamethoxazole) have been associated with clinical exacerbation of porphyria.
Close monitoring of serum potassium is warranted in patients at risk of hyperkalaemia and hyponatraemia.
Co-Trimoxazole has been associated with metabolic acidosis when other possible underlying causes have been excluded. Close monitoring is always advisable when metabolic acidosis is suspected.
Except under careful supervision Co -Trimoxazole should not be given to patients with serious haematological disorders (see 4.8 Undesirable Effects). Co -Trimoxazole has been given to patients receiving cytotoxic therapy with little or no additional effect on the bone marrow or peripheral bloo d.
The combination of antibiotics in Co -Trimoxazole should only be used where, in the judgement of the physician, the benefits of treatment outweigh any possible risks; consideration should be given to the use of a single effective antibacterial agent.

Interaction with laboratory tests: trimethoprim may interfere with the estimation of serum/plasma creatinine when the alkaline picrate reaction is used. This may result in overestim ation of serum/plasma creatinine of the order of 10%. The creatinine clearance is reduced: the renal tubular secretion of creatinine is decreased from 23% to 9% whilst the glomerular filtration remains unchanged.

Zidovudine : in some situations, concomitant treatment with zidovudine may increase the risk of haematological adverse reactions to co -trimoxazole. If concomitant treatment is necessary, consideration should be given to monitoring of haematological parameters.

Cyclosporin: reversible deterioration in renal function has been observed in patients treated with co - trimoxazole and cyclosporin following renal transplantation.

Rifampicin: concurrent use of rifampicin and Co -Trimoxazole results in a shortening of the plasma half-life of trimethoprim after a period of about one week. This is not thought to be of clinical significance.

When trimethoprim is administered simultaneously with drugs that form cations at physiological pH, and are also partly excreted by active renal s ecretion (e.g. procainamide, amantadine ), there is the possibility of competitive inhibition of this process which may lead to an increase in plasma concentration of one or both of the drugs.

Diuretics (thiazides): in elderly patients concurrently receivin g diuretics, mainly thiazides, there appears to be an increased risk of thrombocytopenia with or without purpura.

Pyrimethamine: occasional reports suggest that patients receiving pyrimethamine at doses in excess of 25 mg weekly may develop megaloblastic a naemia should co - trimoxazole be prescribed concurrently.

Warfarin: co-trimoxazole has been shown to potentiate the anticoagulant activity of warfarin via stereo -selective inhibition of its metabolism. Sulfamethoxazole may displace warfarin from plasma - albumin protein-binding sites in vitro. Careful control of the anticoagulant therapy during treatment with Co-Trimoxazole is advisable.

Phenytoin: co-trimoxazole prolongs the half -life of phenytoin and if co -administered could result in excessive phenytoin effect. Close monitoring of the patient's condition and serum phenytoin levels are advisable.

Digoxin: concomitant use of trimethoprim with digoxin has been sho wn to increase plasma digoxin levels in a proportion of elderly patients.

Methotrexate: co-trimoxazole may increase the free plasma levels of methotrexate. If Co - Trimoxazole is considered appropriate therapy in patients receiving other anti - folate drugs s uch as methotrexate, a folate supplement should be considered (see section 4.4).

Trimethoprim interferes with assays for serum methotrexate when dihydrofolate reductase from Lactobacillus casei is used in the assay. No interference occurs if methotrexate i s measured by radioimmuno assay.

Lamivudine: administration of trimethoprim /sulfamethoxazole 160 mg/800 mg (co - trimoxazole) causes a 40% increase in lamivudine exposure because of the trimethoprim component. Lamivudine has no effect on the pharmacokineti cs of trimethoprim or sulfamethoxazole.

Interaction with sulphonylurea hypoglycaemic agents is uncommon but potentiation has been reported.

Hyperkalaemia: caution should be exercised in patients taking any other drugs that can cause hyperkalaemia.

Repaglinide: trimethoprim may increase the exposure of repaglinide which may result in hypoglycaemia.

Folinic acid: folinic acid supplementation has been shown to interfere with the antimicrobial efficacy of trimethoprim -sulfamethoxazole. This has been observed in Pneumocystis jirovecii pneumonia prophylaxis and treatment.

Contraceptives: oral contraceptive failures have been reported with antibiotics. The mechanism of this effect has not been elucidated. Women on treatment with antibiotics should temporarily use a barrier method in addition to the oral contraceptive, or choose another method of contraception.

Pregnancy
Trimethoprim and sulfamethoxazole cross the placenta and their safety in pregnant women has not been established. Case -control studies have shown that there may be an association between exposure to folate antagonists and birth defects in humans.

Trimethoprim is a folate antagonist and, in animal studies, both agents have been shown to cause foetal abnorm alities (see section 5.3).

Co-Trimoxazole should not be used in pregnancy, particularly in the first trimester, unless clearly necessary. Folate supplementation should be considered if Co -Trimoxazole is used in pregnancy.

Sulfamethoxazole competes with bil irubin for binding to plasma albumin. As significantly maternally derived drug levels persist for several days in the newborn, there may be a risk of precipitating or exacerbating neonatal hyperbilirubinaemia, with an associated theoretical risk of kernict erus, when Co-Trimoxazole is administered to the mother near the time of delivery. This theoretical risk is particularly relevant in infants at increased risk of hyperbilirubinaemia, such as those who are preterm and those with glucose -6- phosphate dehydro genase deficiency.

Breast -feeding
The components of Co -Trimoxazole (trimethoprim and sulfamethoxazole) are excreted in breast milk. Administration of Co -Trimoxazole should be avoided in late pregnancy and in lactating mothers where the mother or infant ha s, or is at particular risk of developing, hyperbilirubinaemia.
Additionally, administration of Co -Trimoxazole should be avoided in infants younger than eight weeks in view of the predisposition of young infants to hyperbilirubinaemia.

There have been no studies to investigate the effect of Co -Trimoxazole on driving performance or the ability to operate machinery. Further a detrimental effect on such activities cannot be predicted from the pharmacology of the drug. Nevertheless the clinical status of the patient and the adverse events profile of Co -Trimoxazole should be borne in mind when considering the patients ability to operate machinery.

The frequency categories associated with the adverse events below are estimates. For most events, suitable data for estimating incidence were not available. In addition, adverse events may vary in their incidence depending on the indication.

Data from large published clinical trials were used to det ermine the frequency of very common to rare adverse events. Very rare adverse events were primarily determined from post -marketing experience data and therefore refer to reporting rate rather than a "true" frequency.

The following convention has been used for the classification of adverse events in terms of frequency:

Very common ≥1/10, common ≥1/100 and <1/10, uncommon ≥1/1000 and <1/100, rare ≥1/10,000 and <1/1000, very rare <1/10,000.

* see description of selected adverse reactions

¹ Cholestatic jaundice and hepatic necrosis may be fatal.

Description of selected adverse reactions

Aseptic meningitis

Aseptic meningitis was rapidly reversible on withdrawal of the drug, but recurred in a number of cases on re -exposure to either co -trimoxazole or to trimethoprim alone.

Pulmonary hypersensitivity reactions
Cough, dyspnoea and lung infiltration may be early indicators of respiratory hypersensitivity which, while very rare, has been fatal.

Severe cutaneous adverse reactions (SCARs)
Stevens -Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported (see section 4.4).

Effects associated with Pneumocystis jirovecii Pneumonitis (PJP) management.
Very rare: Severe hypersensitivity reactions, rash, pyrexia, neutropenia, thrombocytopenia, hepatic enzyme increased, hyperkalaemia, hyponatraemia, rhabdomyolysis.
At the high dosages used for PJP management severe hypersensitivity reactions have been reported, necessitating cessation of therapy. Severe hypersensitivity reactions have been reported in PJP patients on re -exposure to co -trimoxazole, sometimes after a dosage interval of a few days.

Rhabdomyolysis has been reported in HIV positive patients rec eiving trimethoprim -sulfamethoxazole for prophylaxis or treatment of PJP.

To report any side effect(s):

•  In Saudi Arabia:

- The National Pharmacovigilance and Drug Safety Center (NPC)  Fax: +966-11-205-7662  SFDA call center 19999  Toll free phone: 8002490000  E-mail: npc.drug@sfda.gov.sa  Website: www.sfda.gov.sa/npc

• Other GCC States

Please contact the relevant competent authority.

Symptoms
Nausea, vomiting, dizziness and confusion are likely signs/symptoms of overdosage. Bone marrow depression has been reported in acute trimethoprim overdosage.

Treatment
If vomiting has not occurred, induction of vomiting may be de sirable. Gastric lavage may be useful, though absorption from the gastrointestinal tract is normally very rapid and complete within approximately two hours. This may not be the case in gross overdosage. Dependant on the status of renal function administrat ion of fluids is recommended if urine output is low.

Both trimethoprim and active sulfamethoxazole are moderately dialysable by haemodialysis. Peritoneal dialysis is not effective.

Pharmacotherapeutic group: Combinations of sulfonamides and trimethoprim, incl. derivatives; ATC code: J01EE01
Mechanism of Action
Sulfamethoxazole competitively inhibits the utilisation of para -aminobenzoic acid in the synthesis of dihydrofolate by the b acterial cell resulting in bacteriostasis. Trimethoprim reversibly inhibits bacterial dihydrofolate reductase (DHFR), an enzyme active in the folate metabolic pathway converting dihydrofolate to tetrahydrofolate. Depending on the conditions the effect may be bactericidal. Thus trimethoprim and sulfamethoxazole block two consecutive steps in the biosynthesis of purines and therefore nucleic acids essential to many bacteria. This action produces marked potentiation of activity in vitro between the two agents.

Trimethoprim binds to plasmodial DHFR but less tightly than to the bacterial enzyme. Its affinity for mammalian DHFR is some 50,000 times less than for the corresponding bacterial enzyme.

Mechanism of resistance
In vitro studies have shown that bacterial resistance can develop more slowly with both sulfamethoxazole and trimethoprim in combination that with either sulfamethoxazole or trimethoprim alone.

Resistance to sulfamethoxazole may occur by different mechanisms. Bacterial mutations cause an increase the concentration of PABA and thereby out - compete with sulfamethoxazole resulting in a reduction of the inhibitory effect on dihydropteroate synthetase enzyme. Another resistance mechanism is plasmid -mediated and results from production of an altered dihy dropteroate synthetase enzyme, with reduced affinity for sulfamethoxazole compared to the wild -type enzyme.

Resistance to trimethoprim occurs through a plasmid -mediated mutation which results in production of an altered dihydrofolate reductase enzyme havin g a reduced affinity for trimethoprim compared to the wild-type enzyme.

Trimethoprim binds to plasmodial DHFR but less tightly than to bacterial enzyme. Its affinity for mammalian DHFR is some 50,000 times less than for the corresponding bacterial enzyme.

Many common pathogenic bacteria are susceptible in vitro to trimethoprim and sulfamethoxazole at concentrations well below those reached in blood, tissue fluids and urine after the administration of recommended doses. In common with other antibiotics, howe ver, in vitro activity does not necessarily imply that clinical efficacy has been demonstrated and it must be noted that satisfactory susceptibility testing is achieved only with recommended media free from inhibitory substances, especially thymidine and t hymine.

Susceptibility testing breakpoints

EUCAST

Enterobacteriaceae : S≤ 2 R> 4
S. maltophilia : S≤ 4 R> 4
Acinetobacter : S≤ 2 R> 4
Staphylococcus : S≤ 2 R> 4
Enterococcus : S≤ 0.032 R> 1
Streptococcus ABCG : S≤ 1 R> 2
Streptococcus pneumoniae : S≤ 1 R> 2
Hemophilus influenza : S≤ 0.5 R> 1 
Moraxella catarrhalis : S≤0.5 R >1
Psuedomonas aeruginosa and other non -enterobacteriaceae : S≤ 2* R> 4*

S = susceptible, R = resistant. *These are CLSI breakpoints since no EUCAST breakpoints are currently available for the se organisms.

Trimethoprim: sulfamethoxazole in the ratio 1:19. Breakpoints are expressed as trimethoprim concentration.

Antibacterial Spectrum
The prevalence of resistance may vary geographically and with time for selected species and local information o n resistance is desirable, particularly when treating severe infections. As necessary, expert advice should be sought when the local prevalence of resistance is such that the utility of the agent in at least some types of infections is questionable. This i nformation gives only an approximate guidance on probabilities whether microorganisms will be susceptible to trimethoprim/sulfamethoxazole or not.

Trimethoprim/sulfamethoxazole susceptibility against a number of bacteria are shown in the table below:

Commonly susceptible species:

Gram-positive aerobes:  Staphylococcus aureus Staphylococcus saprophyticus Streptococcus pyogenes

Gram-negative aerobes: Enterobacter cloacae Haemophilus influenzae Klebsiella oxytoca  Moraxella catarrhalis  Salmonella spp. Stenotrophomonas maltophilia  Yersinia spp.

Species for which acquired resistance may be a problem:

Gram-positive aerobes:  Enterococcus faecalis  Enterococcus faecium  Nocardia spp. Staphylococcus  epidermidis Streptococcus  pneumoniae

Gram-negative aerobes: Citrobacter spp.  Enterobacter aerogenes  Escherichia coli  Klebsiella pneumoniae  Klebsiella pneumonia  Proteus mirabilis  Proteus vulgaris  Providencia spp. Serratia marcesans

Inherently resistant organisms:

Gram-negative aerobes:  Pseudomonas  aeruginosa Shigella spp. Vibrio cholera

 

 

Absorption

After oral administration trimethoprim and sulfamethoxazole are rapidly and nearly completely absorbed. The presence of food does not appear to delay absorption. Peak levels in the blood occur between one and four hours after ingestion and the level attained is dose related. Effective levels persist in the blood for up to 24 hours after a therapeutic dose. Steady state levels in adults a re reached after dosing for 2 -3 days. Neither component has an appreciable effect on the concentrations achieved in the blood by the other.

Distribution

Approximately 50% of trimethoprim in the plasma is protein bound.

Tissue levels of trimethoprim are g enerally higher than corresponding plasma levels, the lungs and kidneys showing especially high concentrations. Trimethoprim concentrations exceed those in
plasma in the case of bile, prostatic fluid and tissue, saliva, sputum and vaginal secretions. Level s in the aqueous humor, breast milk, cerebrospinal fluid, middle ear fluid, synovial fluid and tissue (intestinal) fluid are adequate for antibacterial activity. Trimethoprim passes into amniotic fluid and foetal tissues reaching concentrations approximati ng those of maternal serum.

Approximately 66% of sulfamethoxazole in the plasma is protein bound. The concentration of active sulfamethoxazole in amniotic fluid, aqueous humour, bile, cerebrospinal fluid, middle ear fluid, sputum, synovial fluid and tissue (interstitial) fluids is of the order of 20 to 50% of the plasma concentration.

Biotransformation
Renal excretion of intact sulfamethoxazole accounts for 15 -30% of the dose. This drug is more extensively metabolised than trimethoprim, via acetylation, oxidation or glucuronidation. Over a 72 hour period, approximately 85% of the dose can be accounted for in the urine as unchanged drug plus the major (N4 -acetylated) metabolite.

Elimination
The half-life of trimethopri m in man is in the range 8.6 to 17 hours in the presence of normal renal function. It is increased by a factor of 1.5 to 3.0 when the creatinine clearance is less than 10 ml/minute. There appears to be no significant difference in elderly patients compared with young patients.

The principal route of excretion of trimethoprim is renal and approximately 50% of the dose is excreted in the urine within 24 hours as unchanged drug. Several metabolites have been identified in the urine. Urinary concentrations of t rimethoprim vary widely.

The half-life of sulfamethoxazole in man is approximately 9 to 11 hours in the presence of normal renal function.

There is no change in the half -life of active sulfamethoxazole with a reduction in renal function but there is prolon gation of the half -life of the major, acetylated metabolite when the creatinine clearance is below 25 ml /minute.

The principal route of excretion of sulfamethoxazole is renal; between 15% and 30% of the dose recovered in the urine is in the active form.
Gram-negative aerobes: Pseudomonas aeruginosa Shigella spp.
Vibrio cholera
The pharmacokinetics in the paediatric population with normal renal function of both components of Co-Trimoxazole, TMP and SMZ are age dependent. Elimination of TMP -SMZ is reduced in neonates, during the first two months of life, thereafter both TMP and SM Z show a higher elimination with a higher body clearance and a shorter elimination half -life. The differences are most prominent in young infants (> 1.7 months up to 24 months) and decrease with increasing age, as compared to young children (1 year up to 3 .6 years), children (7.5 years and < 10 years) and adults (see section 4.2).

In elderly patients there is a reduced renal clearance of sulfamethoxazole.

Special patient population

Renal impairment

The elimination half -life of trimethoprim is increased by a factor of 1.5 -3.0 when the creatinine clearance is less than 10 mL/minute. When the creatinine clearance falls below 30 mL/min the dosage of Co -Trimoxazole should be reduced (see section 4.2).

Hepatic impairment
Caution should be exercised when treatin g patients with severe hepatic parenchymal damage as there may be changes in the absorption and biotransformation of trimethoprim and sulfamethoxazole.

Elderly patients
In elderly patients, a slight reduction in renal clearance of sulfamethoxazole but not trimethoprim has been observed.

Paediatric population
See special dosage regimen (see section 4.2).

At doses in excess of recommended human therapeutic dose, trimethoprim and sulfamethoxazole have been reported to cause cleft palate and other foetal abnormalities in rats, findings typical of a folate antagonist. Effects with trimethoprim were preventable by administration of dietary folate. In rabbits, foetal loss was seen at doses of trimethoprim in excess of human therapeutic doses.

Tablets
Sodium starch glycollate Povidone
*Dioctyl sodium sulphosuccinate
*Docusate sodium Magnesium stearate
*alternative ingredients.

See drug interactions.

4 years.

Do not store above 25°C. Keep container in the outer carton.

Amber glass bottles with low density polyethylene snap -fit closures and PVC/Aluminium blister packs.
Pack size: 50 and 100
Round enamelled tins with lever lids. 
Pack size: 5000.

Trimethoprim interferes with assays for serum methotrexate when dihydrofolate reductase from Lactobacillus casei is used in the assay. No interference occurs if methotrexate is measured by radioimmuno assay.

Trimethoprim may interfere with t he estimation of serum/plasma creatinine when the alkaline picrate reaction is used. This may result in overestimation of serum/plasma creatinine of the order of 10%.
Functional inhibition of the renal tubular secretion of creatinine may product a spurious fall in the estimated rate of creatinine clearance.