Trimethoprim
Trimethoprim is an antibiotic for urinary tract infections and traveller's diarrhoea, sold here with sulfamethoxazole as co-trimoxazole tablets in 400/80mg and 800/160mg, under the names Bactrim and Co-trimoxazole.
Co-trimoxazole
Sulfamethoxazole, Trimethoprim
400/80/800/160mg
Co-trimoxazole tablets combine sulfamethoxazole with trimethoprim, in 400/80mg and 800/160mg strengths, for urinary tract infections and other bacterial illness.
What trimethoprim clears up
Most people reach for it because of a urinary tract infection (an infection in the bladder or the tubes that carry urine), which announces itself with burning, urgency and constant trips to the toilet. Trimethoprim stops the bacteria behind those symptoms from multiplying. Given with other medicines, it also treats certain types of pneumonia, and it is used for traveller's diarrhoea. Colds, flu and other viral illnesses are not affected, because there is no bacterium for it to act on.
Two products, one pair of antibiotics
A bacterium that cannot recycle folate cannot copy itself, and trimethoprim shuts down the enzyme that does the recycling. People are spared because we get folate from food. Alongside it sits sulfamethoxazole, which interrupts an earlier step in the same chain, and the partnership reaches more kinds of bacteria than trimethoprim would alone. That pairing is co-trimoxazole, and it is what both products hold.
Bactrim is the brand name and Co-trimoxazole tablets sells under the name of the combination; each is a tablet of 400/80mg or 800/160mg. The numbers run sulfamethoxazole first and trimethoprim second, so the larger tablet carries 800mg with 160mg. Most courses are two tablets a day, morning and evening. Both products sit under Antibiotics.
Side effects, and the ones that need help fast
Most people who have trouble get it in the stomach: nausea, vomiting or loose stools, which usually settle within the first days. Taking the tablet with a meal can calm it, and a mild rash or itching sometimes shows up too. Drink water through the day and finish the course even when the burning has gone.
Some reactions are different. Hives, swelling of the face or throat, and trouble breathing or swallowing need urgent treatment, and so do a sore throat with fever or chills, mouth sores, bruising or bleeding you cannot explain, yellow skin or eyes, unusual paleness, aching joints, or a bluish tinge to the nails, lips or skin.
What not to take alongside it
Potassium is the interaction that matters most. Trimethoprim raises the level in the body, and ACE inhibitors, ARBs (two widely used families of blood pressure medicine) and potassium-sparing water tablets (diuretics) do the same, so together they can push it too high. Co-trimoxazole also strengthens warfarin, a blood thinner, and changes how the body handles methotrexate and phenytoin, an epilepsy medicine.
Sources
- Trimethoprim: MedlinePlus Drug Information — National Library of Medicine
- CDC - Antibiotic Use — CDC
Is Trimethoprim available to order in Hong Kong?
Trimethoprim can be ordered online with delivery to Hong Kong. Both listings, generic Bactrim and Co-trimoxazole tablets, are co-trimoxazole, trimethoprim with sulfamethoxazole, in 400/80mg and 800/160mg. A parcel that does not arrive within the delivery window, or arrives damaged, is sent again free, and if that is not possible the order is refunded.
How much do Trimethoprim products cost in Hong Kong?
Each of the two trimethoprim products has its own price per pack, shown on its page in HKD or your selected currency; larger packs usually cost less per unit.
Do I need a prescription to order Trimethoprim?
PockDose does not ask you to upload a prescription when you order trimethoprim. See the ordering FAQ for details.
What is another name for sulfamethoxazole and trimethoprim?
Bactrim is a brand name of sulfamethoxazole and trimethoprim, which are also sold as Septra and Septrin. Here, sulfamethoxazole and trimethoprim can be bought online as generic Bactrim and co-trimoxazole tablets. These are generics, not the original brand.
Is Co-trimoxazole the same as Bactrim?
Yes. Both products are co-trimoxazole, so each tablet contains sulfamethoxazole with trimethoprim in the same 400/80mg or 800/160mg amounts. The names are the only difference: Bactrim is the familiar brand name, while the other product is sold under the name of the combination.
What do the numbers 400/80mg and 800/160mg mean?
Co-trimoxazole strengths are written as sulfamethoxazole first and trimethoprim second. A 400/80mg tablet holds 400mg of sulfamethoxazole with 80mg of trimethoprim, and the 800/160mg tablet doubles both while keeping the same fixed ratio of the two antibiotics.
How quickly does trimethoprim work for a UTI?
Burning and the constant need to urinate usually begin to ease within the first few days. The infection clears more slowly than the symptoms do, which is why the tablets are still needed after you feel normal again.
Can I take trimethoprim with my blood pressure tablets?
Trimethoprim lifts the potassium level in the body, and so do ACE inhibitors, ARBs and potassium-sparing water tablets, so taking them together can raise potassium too far. Most other blood pressure medicines do not increase potassium.
Does trimethoprim affect the pill?
Trimethoprim and co-trimoxazole do not make the combined pill, the patch or the ring less reliable; only enzyme-inducing antibiotics such as rifampicin and rifabutin do. Vomiting or severe diarrhoea can still stop a pill being absorbed, and that matters for the days you are unwell.