Sulfamethoxazole
Encyclopedia
Sulfamethoxazole is a sulfonamide
bacteriostatic antibiotic
.
It is most often used as part of a synergistic combination with trimethoprim
in a 5:1 ratio in co-trimoxazole (abbreviated SMZ-TMP and SMX-TMP, or TMP-SMZ and TMP-SMX), also known under trade names such as Bactrim
, Septrin, or Septra; in Eastern Europe
it is marketed as Biseptol. Its primary activity is against susceptible forms of Streptococcus
, Staphylococcus aureus
(including MRSA
), Escherichia coli
, Haemophilus influenzae
, and oral
anaerobes. It is commonly used to treat urinary tract infections. In addition it can be used as an alternative to amoxicillin
-based antibiotics to treat sinusitis
. It can also be used to treat toxoplasmosis
and it is the drug of choice for Pneumocystis pneumonia
, which affects primarily patients with HIV.
Other names include: sulfamethylisoxazol, sulfisomezole, MS 53, RO 4 2130, and sulfamethazole.
(PABA). They inhibit normal bacterial utilization of PABA for the synthesis of folic acid
, an important metabolite in DNA synthesis
. The effects seen are usually bacteriostatic in nature. Folic acid is not synthesized in humans, but is instead a dietary requirement. This allows for the selective toxicity to bacterial cells (or any cell dependent on synthesizing folic acid) over human cells. Bacterial resistance to sulfamethoxazole is caused by mutations in the enzymes involved in folic acid synthesis that prevent the drug from binding to it.
A TMP-SMZ (also TMP-SMX or TMP-Sulfa) disk is a combination of trimethoprim and sulfamethoxazole that acts synergistically for bactericidal action. A bacterial culture impregnated with a trimethoprim and sulfamethoxazole disk may be used to help identify an organism as Gardnerella vaginalis; it is sensitive to the TMP-SMZ disk.
of sulfamethoxazole/trimethoprim is gastrointestinal upset. Allergies to sulfa-based medications typically cause skin rashes, hives, or trouble breathing or swallowing and warrant immediate discontinuation of the medication and contact with doctor immediately. Sulfamethoxazole/trimethoprim is also known to increase blood concentrations of the drug warfarin
(U.S. brand name: Coumadin) and can cause an unexpected increase in clotting time and uncontrolled bleeding. Neutropenia
and thrombocytopenia
also are rare adverse effects to be monitored if a patient is placed on long-term therapy. Sulfamethoxazole is also a Stevens–Johnson syndrome (SJS) inducing substance.
Sulfamethoxazole can also cause nausea, severe stomach, or abdomen pains. Headaches commonly occur when taking sulfamethoxazole. Muscle pains sometimes occur when taking this medicine. If symptoms persist, one should contact his/her physician. If trouble breathing or swelling of the face, mouth, or tongue occurs, one should discontinue the medicine and get emergency medical help. These are often symptoms of a severe allergic reaction.
Sulfamethoxazole/trimethoprim can lead to a megaloblastic anemia in some patients because it is a folate antagonist.
Sulfonamide (medicine)
Sulfonamide or sulphonamide is the basis of several groups of drugs. The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame...
bacteriostatic antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
.
It is most often used as part of a synergistic combination with trimethoprim
Trimethoprim
Trimethoprim is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections.It belongs to the class of chemotherapeutic agents known as dihydrofolate reductase inhibitors...
in a 5:1 ratio in co-trimoxazole (abbreviated SMZ-TMP and SMX-TMP, or TMP-SMZ and TMP-SMX), also known under trade names such as Bactrim
Co-trimoxazole
Trimethoprim/sulfamethoxazole or co-trimoxazole is a sulfonamide antibiotic combination of trimethoprim and sulfamethoxazole, in the ratio of 1 to 5, used in the treatment of a variety of bacterial infections.The name co-trimoxazole is the British Approved Name, and has been marketed worldwide...
, Septrin, or Septra; in Eastern Europe
Eastern Europe
Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region"...
it is marketed as Biseptol. Its primary activity is against susceptible forms of Streptococcus
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
, Staphylococcus aureus
Staphylococcus aureus
Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...
(including MRSA
Methicillin-resistant Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus...
), Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
, Haemophilus influenzae
Haemophilus influenzae
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...
, and oral
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
anaerobes. It is commonly used to treat urinary tract infections. In addition it can be used as an alternative to amoxicillin
Amoxicillin
Amoxicillin , formerly amoxycillin , and abbreviated amox, is a moderate-spectrum, bacteriolytic, β-lactam antibiotic used to treat bacterial infections caused by susceptible microorganisms. It is usually the drug of choice within the class because it is better absorbed, following oral...
-based antibiotics to treat sinusitis
Sinusitis
Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...
. It can also be used to treat toxoplasmosis
Toxoplasmosis
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...
and it is the drug of choice for Pneumocystis pneumonia
Pneumocystis pneumonia
Pneumocystis pneumonia or pneumocystosis is a form of pneumonia, caused by the yeast-like fungus Pneumocystis jirovecii...
, which affects primarily patients with HIV.
Other names include: sulfamethylisoxazol, sulfisomezole, MS 53, RO 4 2130, and sulfamethazole.
Mechanism of action
Sulfonamides are structural analogs and competitive antagonists of para-aminobenzoic acid4-Aminobenzoic acid
4-Aminobenzoic acid is an organic compound with the formula H2NC6H4CO2H. PABA is a white grey crystalline substance that is only slightly soluble in water...
(PABA). They inhibit normal bacterial utilization of PABA for the synthesis of folic acid
Folic acid
Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
, an important metabolite in DNA synthesis
DNA synthesis
DNA synthesis commonly refers to:*DNA replication - DNA biosynthesis *Polymerase chain reaction - enzymatic DNA synthesis *Oligonucleotide synthesis - chemical synthesis of nucleic acids...
. The effects seen are usually bacteriostatic in nature. Folic acid is not synthesized in humans, but is instead a dietary requirement. This allows for the selective toxicity to bacterial cells (or any cell dependent on synthesizing folic acid) over human cells. Bacterial resistance to sulfamethoxazole is caused by mutations in the enzymes involved in folic acid synthesis that prevent the drug from binding to it.
Side effects
The most common side effectAdverse drug reaction
An adverse drug reaction is an expression that describes harm associated with the use of given medications at a normal dosage. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs...
of sulfamethoxazole/trimethoprim is gastrointestinal upset. Allergies to sulfa-based medications typically cause skin rashes, hives, or trouble breathing or swallowing and warrant immediate discontinuation of the medication and contact with doctor immediately. Sulfamethoxazole/trimethoprim is also known to increase blood concentrations of the drug warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
(U.S. brand name: Coumadin) and can cause an unexpected increase in clotting time and uncontrolled bleeding. Neutropenia
Neutropenia
Neutropenia, from Latin prefix neutro- and Greek suffix -πενία , is a granulocyte disorder characterized by an abnormally low number of neutrophils, the most important type of white blood cell...
and thrombocytopenia
Thrombocytopenia
Thrombocytopenia is a relative decrease of platelets in blood.A normal human platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. These limits are determined by the 2.5th lower and upper percentile, so values outside this range do not necessarily indicate disease...
also are rare adverse effects to be monitored if a patient is placed on long-term therapy. Sulfamethoxazole is also a Stevens–Johnson syndrome (SJS) inducing substance.
Sulfamethoxazole can also cause nausea, severe stomach, or abdomen pains. Headaches commonly occur when taking sulfamethoxazole. Muscle pains sometimes occur when taking this medicine. If symptoms persist, one should contact his/her physician. If trouble breathing or swelling of the face, mouth, or tongue occurs, one should discontinue the medicine and get emergency medical help. These are often symptoms of a severe allergic reaction.
Sulfamethoxazole/trimethoprim can lead to a megaloblastic anemia in some patients because it is a folate antagonist.