Abstract: In this update, we found an additional 42 trials and added them to the original 254 studies. The update consists of 296 trials that evaluated dose-related efficacy of atorvastatin in 38,817 participants. Included are 242 before-and-after trials and 54 placebo-controlled RCTs. Log dose-response data from both trial designs revealed linear dose-related effects on blood total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides. The Summary of findings table 1 documents the effect of atorvastatin on LDL-cholesterol over the dose range of 10 to 80 mg/d, which is the range for which this systematic review acquired the greatest quantity of data. Over this range, blood LDL-cholesterol is decreased by 37.1% to 51.7% (Summary of findings table 1). The slope of dose-related effects on cholesterol and LDL-cholesterol was similar for atorvastatin and rosuvastatin, but rosuvastatin is about three-fold more potent. Subgroup analyses suggested that the atorvastatin effect was greater in females than in males and was greater in non-familial than in familial hypercholesterolaemia. Risk of bias for the outcome of withdrawals due to adverse effects (WDAEs) was high, but the mostly unclear risk of bias was judged unlikely to affect lipid measurements. Withdrawals due to adverse effects were not statistically significantly different between atorvastatin and placebo groups in these short-term trials (risk ratio 0.98, 95% confidence interval 0.68 to 1.40). This update resulted in no change to the main conclusions of the review but significantly increases the strength of the evidence. Studies show that atorvastatin decreases blood total cholesterol and LDL-cholesterol in a linear dose-related manner over the commonly prescribed dose range. New findings include that atorvastatin is more than three-fold less potent than rosuvastatin, and that the cholesterol-lowering effects of atorvastatin are greater in females than in males and greater in non-familial than in familial hypercholesterolaemia. This review update does not provide a good estimate of the incidence of harms associated with atorvastatin because included trials were of short duration and adverse effects were not reported in 37% of placebo-controlled trials.

Plain-language summary: This represents the first update of this review, which was published in 2012 (Adams 2012). Atorvastatin is one of the most widely prescribed drugs and the most widely prescribed statin in the world. It is an HMG-CoA reductase inhibitor that is prescribed to prevent adverse cardiovascular events and to lower blood total cholesterol and LDL-cholesterol. It is therefore important to know the magnitude of the effect that atorvastatin has on cholesterol. We searched for all evidence obtained from three- to 12-week trials reporting the effect of atorvastatin on blood cholesterol. This update found 42 additional trials and reports on 296 trials in 38,817 participants. Atorvastatin showed a consistent effect in lowering blood cholesterol over the dose range of 2.5 to 80 mg daily. The effect was greater with higher doses than with lower doses. Atorvastatin works similarly to rosuvastatin in lowering cholesterol but is about three-fold less potent. Risk of bias for all assessed trials was high. Review authors were unable to assess harms of atorvastatin because the included trials were too short, and because only 34 included trials assessed harms.