Simvastatin

Simvastatin belongs to the statin family. It enters the body in an inactive form, a prodrug, which must first be activated before it can act. Once activated, it blocks HMG-CoA reductase, the enzyme that controls the rate-limiting step in cholesterol production. This enzyme converts HMG-CoA into mevalonic acid, the starting point of the entire mevalonate pathway.

By slowing this internal production, simvastatin lowers the level of cholesterol circulating in the blood and reduces its deposition in the artery walls. This deposition is the mechanism that forms the plaques responsible for heart attack and stroke. The mevalonate pathway does not serve cholesterol alone: it also feeds the synthesis of other molecules such as coenzyme Q10, a point we will return to. Its half-life is short, two to five hours, which explains the dosing rhythm described below.

Simvastatin is indicated for hypercholesterolaemia, whether familial or not, as well as for hypertriglyceridaemia and dysbetalipoproteinaemia. Beyond these lipid profile abnormalities, it pursues a broader goal: reducing the occurrence of cardiovascular events. This is why it is prescribed both to prevent a first event in people at risk and to avoid a recurrence.

The strength of this effect has been measured across large groups of patients. A meta-analysis of 26 trials bringing together about 170,000 participants showed that each 1.0 mmol/L reduction in LDL cholesterol under statin therapy clearly reduces the incidence of heart attacks, revascularisations and ischaemic strokes. In other words, the benefit follows the magnitude of the LDL reduction. This dose-effect relationship is the foundation that justifies aiming for a cholesterol target and maintaining it over time.

Simvastatin is taken orally, once a day, in the evening. This choice of the evening is not trivial: the liver produces most cholesterol during the night, and the drug’s short half-life, two to five hours, means an evening dose covers this production window better. Regularity matters more than the exact time: it is the daily intake, day after day, that maintains the effect on cholesterol.

The treatment works only as long as it is taken, and cholesterol rises again once it is stopped. It should therefore not be interrupted on one’s own initiative, even when the lipid profile has returned to normal, because it is precisely the treatment that holds this result. Any change, dose or discontinuation, is decided with the doctor. The highest dose, 80 mg per day, is reserved for patients already stabilised on it for at least twelve months, because of an increased muscle risk at high doses.

The most frequently reported effects are headaches, muscle pain, digestive disturbances and a rise in transaminases, the liver enzymes. The British health service classifies among the common effects, affecting more than one person in a hundred, headaches, nausea, digestive disturbances, muscle pain and sleep disturbances. These manifestations are most often mild, but they deserve to be reported when they persist.

The serious muscle risk, for its part, depends strongly on the dose. In the SEARCH trial, myopathy occurred in 0.9% of patients treated with 80 mg compared with 0.03% on 20 mg per day. Myopathy combines muscle pain or weakness with a creatine phosphokinase raised to more than three times the normal level. Its severe form, rhabdomyolysis, remains rare: it calls for seeking medical advice without delay in the face of cramps, muscle pain or weakness, or dark urine.

Diet works on the same ground as your treatment. Soluble fibre is the best-established example: the beta-glucans in oats and barley capture part of the cholesterol in the gut and limit its passage into the blood. They are also found in pulses, lentils, chickpeas and beans, as well as in apples. Oily fish, olive oil and nuts provide good fats that complement this approach.

The nutritional side of statins has a particular feature. By blocking the mevalonate pathway, the treatment lowers the level of coenzyme Q10 in the blood, a nutrient that uses the same production pathway. A link between this reduction and muscle pain has been proposed, but it remains debated and is not proven to date. Yet the plate provides little coenzyme Q10, mainly through meats and oily fish such as salmon and sardines, and the body makes the greater part of it itself. When this internal production slows, diet alone does not close the gap, and that is where a targeted intake makes sense, in addition to your treatment, never in its place.

Simvastatin is processed by the liver enzyme CYP3A4, which explains several precautions. It is contraindicated with strong inhibitors of this enzyme: clarithromycin, ketoconazole, itraconazole, HIV protease inhibitors and ciclosporin, as well as with gemfibrozil. Other medicines impose a dose ceiling: 10 mg at most with verapamil or diltiazem, 20 mg with amiodarone or amlodipine. For the same reason, grapefruit and its juice, which inhibit CYP3A4 and increase exposure to the drug, should be avoided or clearly separated from the dose.

Monitoring accompanies the treatment. A lipid profile is assessed four weeks after initiation, then periodically, to check that the target is reached and maintained. Added to this is monitoring of the liver enzymes and creatine kinase, particularly in the presence of signs of liver or muscle involvement. Finally, simvastatin is contraindicated in active liver disease, during pregnancy and breastfeeding.