Summary

SLCO1B1 rs4149056 determines how efficiently your liver clears statins from the bloodstream — the C allele impairs hepatic uptake, causing statins (especially simvastatin) to accumulate in blood and muscle tissue, increasing myopathy risk up to 17-fold and guiding which statin you should be prescribed.

Genotype spectrum

TT (Val174/Val174)

Full statin transporter function. Statins reach the liver efficiently, minimising systemic exposure.

TC/CT (Val174/Ala174)

You know which statins to be cautious with. This knowledge prevents trial-and-error prescribing.

CC (Ala174/Ala174)

Interventions have outsized impact for you — knowing this genotype prevents a potentially dangerous prescription. The most important pharmacogenomic finding for statin safety.

Practical takeaway

For TT Carriers (Normal Transport)
• No pharmacogenomic restriction on statin choice or dose.
• Standard myopathy monitoring applies.
For TC Carriers (Intermediate Transport)
• Avoid simvastatin >20mg/day. Lower doses may be tolerable but discuss SLCO1B1 status with prescriber.
• Preferred alternatives: Pravastatin, rosuvastatin, or fluvastatin — less OATP1B1-dependent.
• Share this result with your GP or prescriber before starting or changing statin therapy.
• Monitor: Report unexplained muscle pain, tenderness, weakness, or dark urine immediately.
For CC Carriers (Poor Transport)
• Do not take simvastatin. CPIC-recommended: avoid entirely.
• If statins are needed: Pravastatin or rosuvastatin at reduced starting doses with careful titration.
• Share this result with your prescriber — this is a clinically actionable pharmacogenomic finding.
• CK monitoring may be appropriate when initiating any statin therapy.

Expected response window: Myopathy typically presents within the first year of statin therapy, often within the first few months at higher doses.

Evidence detail

What This Gene Does

SLCO1B1 encodes the OATP1B1 transporter protein, which sits on the surface of hepatocytes (liver cells) and actively transports statins from the bloodstream into the liver — where they need to be to work. Statins lower cholesterol by inhibiting HMG-CoA reductase inside liver cells. If OATP1B1 transport is impaired, statins stay in systemic circulation longer, increasing muscle tissue exposure and the risk of statin-induced myopathy and rhabdomyolysis.

The rs4149056 variant (T>C, Val174Ala) reduces OATP1B1 transport function. This is the single most validated pharmacogenomic marker for statin adverse effects and is included in CPIC (Clinical Pharmacogenetics Implementation Consortium) guidelines.

Mechanism

OATP1B1 is expressed on the sinusoidal (blood-facing) membrane of hepatocytes. It mediates the first-pass extraction of statins from portal blood into liver cells.

Blood → [OATP1B1 transporter] → Hepatocyte → HMG-CoA reductase inhibition → ↓Cholesterol
↑
rs4149056 C allele
impairs this step

When OATP1B1 is impaired (C allele), statins that depend on this transporter are not efficiently cleared from systemic circulation. Higher plasma statin concentrations increase exposure to skeletal muscle, where statins can impair mitochondrial function, deplete CoQ10, and disrupt calcium signalling — the mechanisms underlying statin myopathy.

Simvastatin is the most affected because it is a lactone prodrug that relies heavily on hepatic uptake for activation and clearance. Pravastatin and rosuvastatin use additional transport pathways (including OATP1B3 and renal excretion), making them less dependent on OATP1B1 alone.

SLCO1B1

Summary

Genotype spectrum

Practical takeaway

Evidence detail

Sources (4)