Common side effects observed with statin therapyThomson PD et al., JACC 2016
Statin-associated side effects
Thomson PD, Panza G, Zaleski A, et al.
IntroductionStatins are hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors that are well tolerated but are associated with various statin-associated symptoms (SAS) like statin-associated muscle symptoms (SAMS), diabetes mellitus (DM) and central nervous system (CNS) complaints. It is not clear whether statins are the direct cause of these symptoms. Nevertheless, they often result in reduction or discontinuation of therapy. SAS is favoured over the term statin intolerance because many patients with SAS can tolerate reduced doses of these drugs. A meta-analysis of 15 studies observed a 45% and 15% increase in all-cause mortality respectively CVD events in patients taking less than 80% of their prescribed statin versus patients who were more adherent . Some patients tolerate one statin better than another.
Statin-associated muscle symptoms (SAMS)SAMS are the most common SAS and are reported in 10-25% of statin-treated patients [2,3]. SAMS can occur without creatinine kinase (CK) elevations. Syndromes range from myalgia to marked CK elevations and/or clinical rhabdomyolysis. Several definitions of SAMS have been proposed [4-7], but these are useful for quantifying SAMS in clinical trials but less useful in clinical practice.
Diagnosis of SAMSThe diagnosis of SAMS is often subjective for patient and physician because there are no validated clinical tests or diagnostic criteria. The National Lipid Association (NLA) proposed a point/scoring system on the basis of observational studies, such as the PRIMO and STOMP studies [2,6,8]. Consensus maintains that muscle pain and aching (myalgia), cramps and weakness can be manifestations of SAMS. Symptoms are usually bilateral and involve large muscle groups. In contrast, cramping is usually unilateral and may involve small muscles of the hand and feet. Symptoms may be more frequent in physically active patients . Symptoms often appear early after starting therapy or after increasing a dose and SAMS should usually resolve or reduce within weeks after discontinuation of therapy. Several clinical trials have been performed to identify SAMS but these illustrate the difficulty to recognize them [2,8-11]. This hampers also estimation of incidence and prevalence of SAMS.
Risk of SAMSThe risk of SAMS may be increased by increased serum statin concentrations (such as increased dose, affected statin intestinal absorption, catabolism or metabolism) or reduced body muscle mass. Furthermore, female sex, advanced age, physical disability and a lower body mass index are associated with lower plasma volumes and reduced muscle mass and are SAMS risk factors [12,13]. Also compounds such as alcohol affect muscles and may increase the risk of SAMS. Serious SAMS are more frequent with simvastatin than with other available statins and therefore the FDA recommend avoiding the 80 mg dose .
The only SAMS that do not directly disappear after cessation of therapy are statin-induced necrotising autoimmune myopathy (SINAM). This presents with proximal muscle weakness, markedly elevated CK levels and persistence of symptoms and CK elevations despite drug discontinuation . Most patients harbour antibodies against HMG-CoA which can be detected with the enzyme-linked immunosorbent assay (ELISA) . SINAM is associated with human leukocyte antigen (HLA) genotypes  and recognition of SINAM is important because therapy is required to prevent progression to sever and often irreversible muscle weakness.
Statin-induced necrotising autoimmune myopathy
Managing patients with possible SAMS and other SAS requires reassessing the benefit of statin therapy, making the tentative diagnosis, eliminating contributing factors, reassuring the patient, trying alternative statins and doses and prescribing alternative treatment strategies. CK measurements can be useful to exclude clinically threatening muscle injury and to assist with diagnosis . It is important to exclude other potentially contributing factors. The authors of this paper consider it critical to reassure patients that statins are extremely safe and effective and that SAMS is reversible with drug cessation as may patients are concerned about the side effects. Medications other than statins, which may be out-of-favour, should also be considered, like niacin .
Management of SAMS
Possible mechanisms that produce SAMSStatins inhibit HMG-CoA reductase, a rate-limiting enzyme of the mevalonate pathway. This pathway produces cholesterol, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) . FPP and GGPP can activate a variety of small guanosine triphosphate (GTP)-binding regulatory proteins. Multiple mechanisms have been suggested as contributing to SAMS. These include reduced sarcolemmal or t-tubule cholesterol, affecting the phosphoinositide 3-kinase (PI3K)/AKT pathway and impairment of mitochondrial function [20-22].
Statins and diabetes mellitusContradicting results are reported by clinical trials regarding the relationship of statin therapy with diabetes mellitus (DM), but this affected by the patient inclusion criteria [23,24]. Two meta-analyses both reported a small increase in incidence related to statin treatment, and 1 additional case of DM per year would occur for every 498 patients treated with intense versus moderate statin therapy, which translates to the prevention of 3.2 CVD events for each new case of DM when using intense statin therapy [25,26]. The risk of DM during statin therapy increases with the usual DM risk factors, statin dose and ethnicity .
How statins increase the risk of DM is not clear, but the lower cholesterol levels produced by statins may contribute to the effect. High serum cholesterol levels are associated with a reduced risk of DM. Interestingly, the magnitude of LDL-C increase in FH patients varies with the genetic defect . Patients with genetic defects blocking LDL receptor synthesis have LDL levels greater than in patients with a defective, but synthesized, LDL receptor. Consistent with the concept that increased LDL-C “protects” against DM, the prevalence of DM was lower in LDL receptor-negative patients than those with defective receptors than those with apoB defects. Similarly a meta-analysis demonstrated 2 single-nucleotide polymorphisms in the HMG-CoA reductase gene that reduced LDL-C levels and increased the risk of DM .
Statin effect on the central nervous systemStatins have possible adverse effects (AEs) on cognition. There are some reports of statin-associated memory loss or dementia that often resolve with cessation of statin therapy . However, the number of reports is low but effects on memory may be easily overlooked or mistakenly attributed to aging or concurrent disease . The statin-effect on cognition is controversial but strong evidence linking statins to AEs is lacking, as compared with a larger body of evidence supporting their safety.
Possible mechanisms for CNS effects by statinsStatins could affect the CNS directly by inhibiting the CNS cholesterol synthesis or indirectly by altering other substance involved in cognitive function. Directly inhibition seems unlikely due to the low turn-over of cholesterol in the brain . As statins differ in their ability to cross the blood-brain barrier due to their lipophilic or hydrophilic characters, the possible effect of any statin probably depends on the statin itself as well as on its dose and duration of treatment.
Other SASAfter performing a Pubmed search for relevant meta-analyses and reviews, the authors suggest other possible statin-associated effects. These include liver failure, decreased renal function, tendon ruptures, haemorrhagic stroke, low testosterone, depression, interstitial lung disease and sleep.
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