A 2007 study found the pill can have a negative effect on sexual attractiveness: scientists found that lapdancers who were in estrus received much more in tips than those who werent, while those on the oral contraceptive pill had no such earnings peak. Depression
Low levels of serotonin, a neurotransmitter in the brain, have been linked to depression. High levels of estrogen, as in first-generation COCPs, and progestin, as in some progestin-only contraceptives, have been shown to lower the brain serotonin levels by increasing the concentration of a brain enzyme that reduces serotonin. A growing body of research evidence has suggested that hormonal contraception may have an adverse effect on womens psychological health. In 2016, a large Danish study of one million women (followed-up from January 2000 to December 2013) showed that use of COCPs, especially among adolescents, was associated with a statistically significantly increased risk of subsequent depression, although the sizes of the effects are small (for example, 2.1% of the women who took any form of oral birth control were prescribed anti-depressants for the first time, compared to 1.7% of women in the control group). Similarly, in 2018, the findings from a large nationwide Swedish cohort study investigating the effect of hormonal contraception on mental health amongst women (n=815,662, aged 12–30) were published, highlighting an association between hormonal contraception and subsequent use of psychotropic drugs for women of reproductive age. This association was particularly large for young adolescents (aged 12–19).
Escherichia coli
Proteus mirabilis
Klebsiella pneumoniae
Enterobacter species
Coagulase-negative Staphylococcus species, including S. saprophyticus
Streptococcus pneumoniae
Haemophilus influenzae

Side effects
Common
Nauseas
Change in taste
Vomiting
Diarrhea
Rashes
Sun sensitivity
Itchiness

Rare
Can cause thrombocytopenia (low levels of platelets) by lowering folic acid levels; this may also cause megaloblastic anemia. Trimethoprim antagonizes the epithelial sodium channel  in the distal tubule, thus acting like amiloride. This can cause increased potassium levels in the body (hyperkalemia). Can compete with creatinine for secretion into the renal tubule. This can cause an artificial rise in the serum creatinine. Use in EHEC infections may lead to an increase in expression of Shiga toxin. Contraindications
Known hypersensitivity to trimethoprim
History of megaloblastic anemia due to folate deficiency

Pregnancy
Based on the studies that show that trimethoprim crosses the placenta and can affect folate metabolism, there has been growing evidence of the risk of structural birth defects associated with trimethoprim, especially during the first trimester of pregnancy. It may be involved in a reaction similar to disulfiram when alcohol is consumed after it is used, in particular when used in combination with sulfamethoxazole. The trophoblasts in the early fetus are sensitive to changes in the folate cycle. A recent study has found a doubling in the risk of miscarriage in women exposed to trimethoprim in the early pregnancy. Mechanism of action
Trimethoprim binds to dihydrofolate reductase and inhibits the reduction of dihydrofolic acid (DHF) to tetrahydrofolic acid (THF). THF is an essential precursor in the thymidine synthesis pathway and interference with this pathway inhibits bacterial DNA synthesis.