FOMULA: C₁₄H₁₈N₄O₃ 
Mol. mass: 290.32 g/mol 
EINECS: 212-006-2 
Index of Refraction: 1.608
Molar Refractivity: 80.25 cm³
Molar Volume: 231.8 cm³
Surface Tension: 53.9 dyne/cm
Density: 1.252 g/cm³
Flash Point: 271.9 °C
Enthalpy of Vaporization: 80.02 kJ/mol
Boiling Point: 526 °C at 760 mmHg
Vapour Pressure: 3.74E-11 mmHg at 25°C 
Storage temp of Trimethoprim is 2-8°C.Trimethoprim,its melting point is about  199-203 °C;appearance is white powder|
Stability: Stable. Incompatible with strong oxidizing agents, acids
Water solubility is less than 0.1 g/100 mL at 24 ^oC
Product Categories: Pharmaceutical;Inhibitors;Intermediates & Fine Chemicals;Pharmaceuticals;Peptide Synthesis/Antibiotics
 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5) belongs to the class of chemotherapeutic agents known as dihydrofolate reductase inhibitors. It was formerly marketed by GlaxoSmithKline under trade names including Monotrim,  Proloprim and Triprim.In clinical use it is often abbreviated TRI or TMP; its common laboratory abbreviation is W.
Following is the molecular structure of 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5):

 

Since 1980 in the UK,Trimethoprim was used as monotherapy,it is indicated for the prophylaxis and treatment of urinary tract infections. Co-trimoxazole, with its greater efficacy against a limited number of bacteria, remains indicated for some infections.

 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5) is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections. It was commonly used in a 1:5 combination with Sulfamethoxazole , a sulfonamide antibiotic , which inhibits an earlier step in the folate synthesis pathway.

Hazard Codes: T
Risk Statements: 25 
R25: Toxic if swallowed
Safety Statements: 45 
S45: In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)
RIDADR: 3249
WGK Germany: 3
RTECS: UV8225000
F: 8-10-21 
F 8: Photosensitive
F 10: Keep under argon
F 21: Sensitive to humidity
HazardClass: 6.1(b)
PackingGroup: III 
Use of 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5) is contraindicated during pregnancy, especially the first trimester, and for sufferers of certain blood disorders. It is contraindicated to use trimethoprim during pregnancy, especially the first trimester, and for sufferers of certain blood disorders. 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5) also may be involved in a reaction similar to disulfiram when alcohol is consumed after it is used, particularly when used in combination with sulfamethoxazole .It can also reduce clearance of creatinine at renal tubules.

Tetrahydrofolic acid is an essential precursor in the de novo synthesis of the intermediate THYMIDINE monophoshpate (dTMP), precursor of DNA metabolite THYMIDINE triphosphate. 2,4-Diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (CAS NO.738-70-5) is also called as Trimethoprim ; Bactrim ; Bactrim ; Cotrim ; SMZ/TMP ; Septra ; Sulfatrim ; 2,4-Pyrimidinediamine, 5-((3,4,5-trimethoxyphenyl)-methyl)- ; 5-((3,4,5-Trimethoxyphenyl)methyl)-2,4-pyrimidinediamine ; 5-25-13-00429 (Beilstein Handbook Reference) ; Abaprim ; Anitrim ; BRN 0625127 ; Bacidal ; Bacticel ; CCRIS 2410 ; Co-Trimoxizole ; Cotrimel ; EINECS 212-006-2 ; Espectrin ; Fortrim ; Kombinax ; Monoprim ; Pancidim ; Resprim Forte ; Sinotrim ; Sulmeprim ; Trimethoprime [INN-French] ; UNII-AN164J8Y0X ; Velaten ; component of Bactrim and so on.