Genotoxic effect of Anovlar 21, an oral contraceptive, on mouse bone marrow

Anovlar 21, a combination drug containing the oestrogen ethinyloestradiol and the progestin norethisterone acetate, was studied for its in vivo genotoxic effect on the bone marrow cells of Swiss albino mice. The chromosomal aberration assay and the micronucleus test were employed for the study. 0.08, 0.4, 0.8, 1.6, 3.2, 4.8, 6.4 and 8.0 mg/kg/day of the drug was orally administered for 15 consecutive days to mice. Bone marrow preparations were made 24 h after the final feeding. The lowest dose, 0.08 mg/kg, represents the human therapeutic range. Marrow preparations of mice fed 0.8 mg/kg/day for 15 days were made at 6, 12, 24, 48 and 96 h, and 1, 2 and 3 weeks and a time-yield analysis was carried out. Statistically significant increases in chromosomal aberrations were observed in animal groups fed doses of greater than or equal to 0.4 mg/kg/day. In the time-response study, the maximum frequency of aberrations was noted at 24 h, thereafter decreasing gradually with increasing time. But the drug did not induce a significant increase in the number of micronuclei in bone marrow erythrocytes at any of the doses or time intervals studied.     

The effects of oestrogens and progesterone on oestrogen receptors in female rat liver.

The administration of oestradiol-17 beta or ethynyloestradiol as well as the synthetic progestogen norethisterone acetate resulted in translocation of the oestrogen receptor. Progesterone and the synthetic progestogen (+)-norgestrel were ineffective. The increases in nuclear oestrogen receptor content 1 h after injection of each steroid were similar but different subsequently. The increase with oestradiol-17 beta extended for 3--6 h and for at least 9 h with ethynyloestradiol. With norethisterone acetate, nuclear content was still increased after 24 h. Oestrogen injection resulted in cytosol receptor depletion and a 'deficit' in receptor content extending for 6 h, whereas norethisterone acetate-induced translocation was quantitative. With injections of norethisterone acetate + ethynyloestradiol the increase at 1 h and retention of the nuclear receptors were similar to that with norethisterone acetate alone. In contrast, the depletion of cytosol receptor and its restoration were similar to that seen with ethynyloestradiol alone, suggesting that norethisterone acetate did not interfere with the oestrogen receptor replenishment. Specific binding in vitro of [3H]oestradiol-17 beta in liver cytosols was inhibited by (+)-norgestrel and norethisterone acetate, but not progesterone, at concentrations of 10--100 microM. Nuclear receptors present after norethisterone acetate injection bound oestrogen with high affinity (Kd = 1.52 nM), similar to receptors of oestrogen-injected animals. In the uterus, differential retention of nuclear receptors in response to oestrogens is associated with different cellular responses. The differences in the response of the receptor system in liver to the various steroids suggests that the corresponding tissue responses may also be dissimilar. These results are discussed in relation to the problems of liver dysfunction in oral-contraceptive users.     

Binding of progestagens to receptor proteins in MCF-7 cells

With the aim of finding an explanation for the biological properties of progestagens currently used for contraceptive purposes, we have assessed their specificity for progesterone, androgen and oestrogen receptors in MCF-7 cells. The specificity of progestagens for the progesterone receptors in the cytosol fraction of MCF-7 cells was similar to that for progesterone receptors in human and rabbit myometrial cytosol but different from that for the progesterone receptor in rat myometrial cytosol. At 37 degrees C the relative affinity of 3-keto-desogestrel, the major metabolite of desogestrel, for the progesterone receptor in intact MCF-7 cells was twice that of levonorgestrel and Org 2058, three times that of medroxy-progesterone acetate (MPA), 4.5 times that of norethisterone and 5 times that of progesterone and cyproterone acetate whereas at 4 degrees C in the cytosol fraction of MCF-7 cells exposed to molybdate (nontransformed receptor complexes) 3-keto-desogestrel and Org 2058 displayed similar affinity. The stronger binding of 3-keto-desogestrel in intact cells was due to the higher stability of its complex with the progesterone receptor. At 37 degrees C the relative affinity of 3-keto-desogestrel for the androgen receptor in intact MCF-7 cells was half that of levonorgestrel, similar to that of norethisterone and medroxyprogesterone acetate (MPA) and at least three times higher than that of progestagens with anti-androgenic activity whereas at 4 degrees C in the cytosol fraction exposed to molybdate there was no clear difference between the relative affinities of progestagens with androgenic and anti-androgenic properties. Of the progestagens tested in this study, only norethinodrel displayed measurable but very low relative affinity for the oestrogen receptor in MCF-7 cells. We conclude that the present results of binding studies with intact MCF-7 cells correlate better with the known hormonal properties of progestagens than those obtained with the cytosol fraction exposed to molybdate at 4 degrees C.     

Long-acting contraceptive agents: Structure activity relationships in a series of norethisterone and levonorgestrel esters

A large number of esters of norethisterone (17α-ethynyl-17β-hydroxyestr-4-en-3-one) and levonorgestrel (D-(-)-13β-ethyl-17α-ethynyl-17β-hydroxygon-4-en-3-one) were synthesized and tested for biological activity. The test employed in these studies was the duration of estrus suppression in cycling mature rats. In the norethisterone series several esters exhibited duration of activity comparable to that of norethisterone enarthate. In the levonorgestrel series the butanoic, cyclobutylcarboxylic and cyclopropylcarboxylic esters were longer acting than medroxyprogesterone acetate (17α-acetoxy-6α-methylpregn-4-ene-3, 20-dione) when prepared as aqueous microcrystalline suspensions.     

A novel Candida albicans skin test antigen: efficacy and safety in man

Yeast phase Candida albicans (ATCC No. 10231) was grown in a nonantigenic medium, harvested and lyophilized. Ammonium sulfate fractions of an aqueous extract of the lyophilized cells were evaluated and the fraction yielding the highest specific delayed cutaneous reactivity in sensitized guinea-pigs was used to prepare a C. albicans skin test antigen (CASTA). The safety of the antigen was evaluated by measuring immediate and delayed (0.25, 6, 24, 48 and 72 h) cutaneous reactions in atopic and nonatopic human subjects. The outcome of three repetitive monthly Mantoux skin tests with 0.01-1 microgram antigen doses was used to test for booster effects in 14 subjects and to estimate a safe initial test antigen dose. The utility of a single skin test as a measure of cell-mediated immunity was evaluated in 40 healthy subjects. Reactor rates (greater than or equal to 2 mm, 48 h) of 40% and 85% were detected, respectively, with doses of 0.0316 and 1 microgram. Using a skin test reaction diameter greater than or equal to 5 mm at 48 h, the reactor rate was 50% for the 1-microgram dose. The only adverse reaction (45 mm, 0.25 h) was detected with the 1-microgram dose in an atopic subject who also exhibited exquisite scratch test reaginic hypersensitivity to C. albicans allergen. The prevalence of other adverse reactions to this antigen compared favorably with that to other antigens used for recall antigen testing. These studies suggest the 1-microgram CASTA dose can be used for effective, safe recall antigen skin tests.     

Effect of estradiol on tissue glycogen metabolism in exercised oophorectomized rats

The effect of both physiological and pharmacological doses of estradiol on exercise performance and tissue glycogen utilization was determined in oophorectomized estradiol-replaced (ER) rats. Doses of beta-estradiol 3-benzoate (0.02, 0.04, 0.1, 0.2, 1, 2, 4, or 10 micrograms.0.1 ml of sunflower oil-1.100 g body wt-1) were injected 5 days/wk for 4 wk. Controls were sham injected (SI). After treatment, the animals were run to exhaustion on a motorized treadmill. ER animals receiving the 0.02-microgram dose ran significantly longer and completed more total work than the SI group. ER animals receiving doses of greater than or equal to 0.04 microgram ran longer and performed more work than the 0.02-microgram group. At exhaustion, myocardial glycogen content was significantly decreased in animals that were ER with less than or equal to 0.1 microgram, whereas those replaced with doses greater than 0.1 microgram utilized significantly less glycogen. With the 10-micrograms dose no significant decrease in heart glycogen content was observed at exhaustion. A submaximal 2-h run significantly reduced glycogen content in heart, red and white portions of the vastus lateralis, and the livers of SI animals. The latter effect was attenuated in skeletal muscle and liver, and there was no effect in the hearts of the ER animals receiving 2 micrograms. These data indicate that estradiol replacement in oophorectomized rats influenced myocardial glycogen utilization during exhaustive exercise and spared tissue glycogen during submaximal exercise. These glycogen sparing effects may have contributed to the significant improvements in exercise performance observed in this study.     

Reaginic antibody formation in the mouse. X. Possible role of suppressor T cells in transient IgE antibody responses.

The kinetics of IgE antibody response to alum-absorbed dinitrophenyl derivatives of ovalbumin (DNP-OA) was dependent on the dose of immunogen. A persistent IgE antibody response was obtained when high responder BDF1 mice were immunized with a minimum (0.05 microgram) dose. An increase of the immunogen to 10 microgram depressed IgE antibody responses but enhanced IgG antibody responses of both hapten and carrier specificities. Determination of T helper cell activity and B memory cells after immunization with different doses of antigen indicated that minimum immunogen was favorable for developing helper activity, whereas 1 to 10 microgram immunogen were more favorable than a 0.05-microgram dose for developing both IgE and IgG B memory cells. Nevertheless, neither helper T cells nor B memory cells in the spleen explains a transient IgE antibody response to a high (10 microgram) dose of DNP-OA. Evidence was obtained that immunization with 10 microgram OA induced generation of antigen-specific suppressor T cells, which were not detectable after immunization with 0.05 microgram OA. Transfer of suppressor T cells to DNP-OA-primed mice depressed both anti-hapten and anti-carrier IgE antibody responses. The results suggested strongly that suppressor T cells are involved in a transient IgE antibody response to a high-dose immunogen.     

Assessment of Incremental Dosage Regimen of Combined Oestrogen-Progestogen Oral Contraceptive

Eighty-six women of proved fertility used an incremental dosage regimen of a combined oral contraceptive for a total of 570 cycles over one year. A daily tablet containing 50 μg of ethinyloestradiol and 50 μg D-norgestrel was taken for 11 days and a daily tablet containing 50 μg ethinyloestradiol and 125 μg D-norgestrel for the next 10 days. Withdrawal bleeding occurred during the tabletfree interval of seven days. The new preparation proved to be an efficient contraceptive, well tolerated, and with few side effects. Women who had gained weight while taking other oral contraceptives lost weight when they changed to the new preparation. The regimen allowed a significant reduction in the cycle dose of progestogen, and these results suggest that a further reduction in the cycle dose of both oestrogen and progestogen may be possible without losing contraceptive efficiency.     

Venous effects of oral contraceptives

In a five-year analysis of an oral contraceptive trial by the Council for the Investigation of Fertility Control venous effects were the third most troublesome group of side-effects with both combined and sequential therapy. Vein complaints, leg cramps, and thrombophlebitis were significantly more frequent with the combined preparations that contained a relatively low dose of progestogen and a high dose of oestrogen than with the other groups tested. No cases of thrombophlebitis occurred in women taking the strongly oestrogenic sequential groups.Histological examination of uterine curettings showed that most progestogenic combined preparations were associated with a high incidence of dilated endometrial sinusoids, while the oestrogenic sequential regimens and low-dose progestogen-only regimens had a low incidence. The incidence of stromal condensation round the sinusoids correlated with the incidence of leg cramps, and these effects appeared to be specific for each preparation tested.     

Binding of the gestagens norethisterone and levonorgestrel in blood of various species

This study investigates the binding of 2 widely used contraceptive steroids, levonorgestrel and norethisterone, by plasma from various animal species and compares the results to those obtained with human plasma. Equilibrium dialysis of plasma samples and polyacrylamide gel electrophoresis were performed as previously described. The plasma samples were diluted with phosphate-buffered saline on the percentage of levonorgestrel and norethisterone bound in comparison to human plasma. The concentration of total protein and albumin was measured colorimetrically in each sample. An ammonium sulphate precipitation technique measured the level of sex-hormone binding globulin (SHBG). Results of the equilibrium dialysis show that binding of levonorgestrel and norethisterone in plasma was similar in adult female rhesus monkeys and baboons to that of humans with both high-affinity and low-affinity classes of binding sites. The dissociation constants of the high-affinity class for levonorgestrel was 4-fold lower than that for norethisterone in all 3 primates, indicating levonorgestrel was more tightly bound. Total protein and albumin concentrations were also the same in all 3 primates. SHBG levels in female monkeys and baboons however were 3-4 times those found in normal human females. Although differences exist in the binding of the 2 gestagens between human, baboon, and rhesus monkey plasma, there are no significant differences in the metabolism of the gestagens in the 3 primates. Overall, the results indicate that in the human, baboon, and rhesus monkey, binding of norgestrel and norethisterone occur mainly to SHBG, which had a greater affinity for norgestrel than for norethisterone, and to a lesser extent, albumin. Differences in the binding of gestagens between human and nonprimate species (rat, dog, rabbit) studied suggest that only baboon and rhesus monkeys may be considered appropriate animal models for extrapolation of results of contraceptive studies to humans.     

Effects of Progestogen Oral Contraception with Norethisterone on Blood Clotting and Platelets

The effects on clotting tests and platelet function of six months'' continuous administration of the 19-norsteroid, progestogen-only contraceptive, norethisterone, have been studied in four groups of women. In a group of women who have not previously taken oral contraceptive no acceleration of clotting or platelet factors was found, but in contrast a tendency to reduced coagulability was observed. Women who had previously been taking combined oestrogen-progestogen preparations showed reduced clotting and platelet parameters when norethisterone was substituted. No changes in clotting or platelets were found in women who changed from 17-acetoxysteroid progestogen chloramadinone acetate or in a group of women started postpartum.     

Hormone treatment of the adult transsexual patient

Hormonal reassignment has two aims: (1) to reduce the hormonally induced secondary sex characteristics of the original sex and (2) to induce the secondary sex characteristics of the new sex. In Europe, cyproterone acetate is generally used to inhibit androgens in male-to-female transsexuals. Medroxyprogesterone acetate is an acceptable, though less effective, alternative. To induce feminization there is a wide range of oestrogens. Oral ethinyloestradiol is a potent and inexpensive oestrogen, but it may cause venous thrombosis. Oral 17beta-oestradiol valerate or transdermal 17beta-oestradiol is the treatment of choice. The goal of treatment in female-to-male transsexuals is to induce virilization, including a male pattern of sexual hair, a male voice and male physical contours, and to stop menses. The principal hormonal treatment is a testosterone preparation. Hormone-dependent tumours have been encountered and surveillance is necessary.     

Effects of arginine vasotocin on levels of plasma gonadotropins and prolactin in ovariectomized conscious rats

Arginine vasotocin was injected into the third ventricle or intravenously in conscious, ovariectomized rats and its effect on gonadotropin and prolactin release evaluated. The peptide lowered plasma levels of both LH and prolactin in doses of 40 or 100 ng given intraventricularly. The higher dose was slightly more effective than the lower dose. Intravenous injection of a 1-microgram dose of vasotocin failed to alter plasma LH in the ovariectomized animals; however, a 5-micrograms dose induced a slight depression apparent at only 60 min following injection. Intravenous injection of 1 microgram produced a significant lowering of plasma prolactin, whereas a dramatic lowering followed the injection of the higher dose. Plasma FSH was unaffected in these experiments. Incubation of dispersed anterior pituitary cells from ovariectomized rats with various doses of vasotocin revealed no effect of the peptide on the release of FSH, LH, or prolactin. It also did not alter the response to LHRH, but it partially blocked the action of dopamine to inhibit prolactin release. The data indicate that quite low doses of arginine vasotocin act within the brain to inhibit LH and prolactin secretion in ovariectomized, conscious animals.     

Effect of the progestogens, gestodene, 3-keto desogestrel, levonorgestrel, norethisterone and norgestimate on the oxidation of ethinyloestradiol and other substrates by human liver microsomes

A number of different progestogens, levonorgestrel (LNG), norethisterone (NET), gestodene (GSD), desogestrel (DG) and norgestimate (NORG) are used in combination with the oestrogen ethinyloestradiol (EE2) in oral contraceptive steroid preparations. All the progestogens are acetylenic steroids and previous studies have indicated the potential of acetylenic steroids to cause mechanism-based or "suicide" inactivation of cytochrome P-450. We have compared the effects of the different progestogens on EE2 2-hydroxylation (a reaction catalyzed by enzymes from the P-450IIC, P-450IIIA and P-450IIE gene families) and also the oxidative metabolism of other drug substrates (cyclosporin, diazepam, tolbutamide) by human liver microsomes. On coincubation with EE2 as substrate, GSD, 3-keto desogestrel (3-KD, the active metabolite of desogestrel) and LNG produced some concentration-dependent inhibition of EE2 2-hydroxylation (maximum 32% inhibition at 100 microM 3-keto desogestrel). Ki values determined for GSD and 3-KD were 98.5 +/- 12.3 and 93.2 +/- 10.3 microM (mean +/- SD; n = 4), respectively. Preincubation of progestogens in a small volume (50 microliters) incubation for 30 min in the presence of an NADPH-generating system enhanced the inhibitory potential of all the steroids (at 100 microM, inhibition was for GSD 39%, 3-KD 46%, LNG 46%, NET 51% and NORG 43%). Inhibitory effects were therefore comparable and also similar to the macrolide antibiotic troleandomycin. The most marked inhibition seen was of diazepam N-demethylation and hydroxylation by GSD (71 and 57%, respectively) and 3-KD (62 and 50%, respectively). In preincubation studies involving cyclosporin as the substrate, the order of inhibitory potency was GSD greater than 3-KD greater than NET greater than LNG for production of both metabolite M17 and M21. The results of the study indicate that all the progestogens in common use have the propensity to inhibit a number of oxidative pathways but there is little evidence for one progestogen being more markedly inhibitory than others.     

Comparative trial of nafoxidine and ethinyloestradiol in advanced breast cancer: an E.O.R.T.C. study.

A randomized clinical trial of nafoxidine, a non-steroidal oestrogen antagonist, and ethinyloestradiol in postmenopausal patients with advanced breast cancer produced objective remissions in 31% of 49 women receiving nafoxidine and in 14% of 49 receiving ethinyloestradiol. The differences in remission rates was almost significant (0.05 less than P less than 0.10). Life-threatening complications were more frequent with ethinyloestradiol than with nafoxidine but the latter produced specific toxic reactions on skin and hair that may limit its practical usefulness. Synthetic oestrogen antagonists may occupy a privileged place in the treatment of breast cancer, and other representatives of this new class of compounds should be accurately assessed in randomized clinical trials.     

Fine structure of prolactin cell of female albino rat as affected by some antifertility drugs--a comparative electron microscopic study

One antioestrogenic compound as well as some antifertility drugs have been administered to female albino rats over a period of six months to study their long term effects on fine structures in PRL cell. Almost in all the cases, the dynamics of hormone synthesis and secretion have been affected. Fine structure is suggestive of activation of synthetic machinery of the cell. The cell picture under the estradiol valerate regimen presents a transitional stage progressing towards involution due to accelerated cell cycle. Sparse granulation, frequent granule extrusion and misplaced exocytosis under the influence of tamoxifen citrate or levonorgestrel + ethinyloestradiol are similar to those observed in adenomatous PRL cell. Fine structural correlates of stepped up synthesis are also observed following chronic progesterogenic influences of progesterone and norethisterone heptanoate, but the magnitude of the change is on a lower scale. All the fine structural changes have been discussed in the context of ultrastructural pathology.     

Detection and prevalence of pneumococci with increased resistance to penicillin.

Susceptibility to penicillin was determined for 6000 strains of pneumococci isolated during 1974--76 from patients in Alberta and the adjacent region of the Northwest Territories. Strains were considered to be relatively resistant if the minimum inhibitory concentration (MIC) of penicillin was 0.16 microgram (0.26 U)/mL or more, which is eight or more times greater than the MIC for fully susceptible strains. Resistance was detected in 143 strains (2.4%) isolated from 122 patients and belonging to four capsular types. The MIC of the most resistant strains was 0.32 microgram (0.53 U/mL. Penicillin-resistant strains were highly resistant to oxacillin, the MIC being at least 30 times greater than that for penicillin-susceptible strains. Pneumococci resistant to penicillin may readily be detected by the narrowness or absence of a zone of inhibition around a 1-microgram oxacillin disc in susceptibility tests on blood agar. The degree of resistance reported here is relative and does not necessarily preclude successful treatment with full therapeutic doses of penicillin G, but penicillin preparations that give low blood concentrations may not be suitable for treating infections caused by these strains.     

Steroid sequestration and tightly bound oestrogen-protein complexes in human breast tumours and a breast cancer cell line

Homogenates of breast tumours taken at surgery were prepared in phosphate-buffered medium in the presence or absence of the protease inhibitors N-alpha-p-tosyl-L-arginine methyl ester (TAME, 10 mM) or soy bean trypsin inhibitor (STI, 1 mg/ml). Aliquots (0.25 ml) were incubated in 5 ml medium, with the addition of excess trypsin (2 mg/ml) to experimental flasks. Oestrogen was measured by means of a radioreceptor assay (RRA) based on rat or human uterine cytosolic oestradiol receptor. In oestrogen receptor positive (ER +ve) tumour homogenates, TAME decreased while STI increased ethyl acetate extractable oestrogen in these preparations. The addition of trypsin enhanced yields of oestrogen in the TAME, but not in the STI or control (no inhibitor) preparations. None of these treatments affected RRA detectable oestrogen in homogenates of ER -ve tumours. Suspensions of ZR-75-1 cells, prepared in Krebs Ringer bicarbonate (KRBG) incubated with trypsin also gave greatly enhanced yields of extractable oestrogen. Fractionation of oestrogens from both tumour homogenates and from the cell line showed coincidence of RRA detectable steroid with oestradiol and oestrone, and, particularly in trypsin flasks, very non-polar components were also found. In the cell-line extracts, HPLC fractionation combined with specific radioimmunoassays confirmed the presence of both oestradiol and oestrone. The major extracted component was oestrone. The data suggest the existence within breast tumour tissue of sequestered pools of steroid requiring proteolytic action for their release. One possibility, consistent with reports in the literature, is that the steroids may themselves be directly conjugated to protein. Their presence in ER +ve but not ER -ve tumours strongly suggests some relationship to the development of hormone-sensitive disease. Alternatively, the phenomenon may be associated with the rigid compartmentalization of the paracrine function of the tissue.     

Long-acting contraceptive agents: design of the WHO Chemical Synthesis Programme

The great demand for improved long-acting injectable steroid contraceptives, particularly in developing countries, and the relative lack of interest from the pharmaceutical industry to develop such products stimulated WHO to launch a synthetic and screening programme to find improved, safe and acceptable injectable preparations. More than 210 esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) and levonorgestrel (D-(-)-13 beta-ethyl-17 alpha-ethynyl-17 beta-hydroxygon-4-en-3-one) have been prepared in university-based research laboratories situated mainly in developing countries, and then screened by NICHHD in animal models. The following three compounds, levonorgestrel butanoate, cyclopropylcarboxylate and cyclobutylcarboxylate, proved to be particularly long-acting when administered as microcrystalline suspensions. The overall strategy of this research and development programme is described.     

NSAID use selectively increases the risk of non-fatal myocardial infarction: a systematic review of randomised trials and observational studies

Background

Recent clinical trials and observational studies have reported increased coronary events associated with non steroidal anti-inflammatory drugs (NSAIDs). There appeared to be a disproportionate increase in non-fatal versus fatal events, however, numbers of fatal events in individual studies were too small, and event rates too low, to be meaningful.

Objectives

We undertook a pooled analysis to investigate the effect of NSAIDs on myocardial infarction (MI) risk with the specific aim to differentiate non-fatal from fatal events.

Methods

We searched Pubmed (January, 1990 to March, 2010) for observational studies and randomised controlled trials that assessed the effect of NSAIDs (traditional or selective COX-2 inhibitors [coxibs]) on MI incidence separately for fatal and non-fatal events. Summary estimates of relative risk (RR) for non-fatal and fatal MIs were calculated with a random effects model.

Results

NSAID therapy carried a RR of 1.30 (95% CI, 1.20–1.41) for non-fatal MI with no effect on fatal MI (RR 1.02, 95% CI, 0.89–1.17) in six observational studies. Overall, the risk increase for non-fatal MI was 25% higher (95% CI, 11%–42%) than for fatal MI. The two studies that included only individuals with prior cardiovascular disease presented risk estimates for non-fatal MI on average 58% greater (95% CI, 26%–98%) than those for fatal MI. In nine randomised controlled trials, all investigating coxibs, the pooled RR estimate for non-fatal MI was 1.61 (95% CI, 1.04–2.50) and 0.86 (95% CI 0.51–1.47) for fatal MIs.

Conclusions

NSAID use increases the risk of non-fatal MI with no substantial effect on fatal events. Such differential effects, with potentially distinct underlying pathology may provide insights into NSAID-induced coronary pathology. We studied the association between the use of nonsteroidal anti-inflammatory drugs (NSAIDs) and the risk of myocardial infarction (MI), separating non-fatal from fatal events, summarizing the evidence from both observational studies and randomised controlled trials. An increased risk of non-fatal MI was clearly found in both types of studies while use of NSAID did not confer an increased risk of fatal MI. Our findings provide support for the concept that thrombi generated under NSAID treatment could be different from spontaneous thrombi.