The risk of myopathy when treated with HMG-CoA reductase inhibitors is increased when used in combination with cyclosporine, fibrates, macrolide antibiotics (including erythromycin), antifungal agents with azole derivatives or nicotinic acid in lipid-lowering doses (more than 1 g / day).
In some rare cases, these combinations cause rhabdomyolysis, accompanied by renal failure in connection with myoglobinuria. In this regard, a careful assessment of the risk-benefit ratio of combined treatment is necessary.
Atorvastatin metabolism is carried out with the participation of isoenzyme CYP3A4. When using atorvastatin in combination with isoenzyme inhibitors CYP3A4 (E.g., cyclosporine, antibiotics, macrolides, e.g., erythromycin and clarithromycin, nefazodone, antifungal azole derivatives, for example, itraconazole and HIV protease inhibitors) may increase atorvastatin plasma concentration. The degree of influence and potentiation effect is determined by the variability of the effect on the isoenzyme CYP3A4. In this regard, care should be taken with the appointment of atorvastatin in combination with the above drugs.
Atorvastatin and its metabolites are substrates for P-glycoprotein. Inhibitors of the transport protein OATP1B1 (for example, ciclosporin) may increase the bioavailability of atorvastatin.
The simultaneous use of drugs, which reduce the concentration of endogenous steroid hormones (including cimetidine, ketoconazole, spironolactone), increases the risk of reducing the level of endogenous steroid hormones (while the application requires caution).
With simultaneous application of atorvastatin and erythromycin (500 mg four times a day) or clarithromycin (500 mg, 2 times a day), which inhibits isozyme CYP3A4, an increase in the concentration of atorvastatin in the blood plasma was observed.
With the simultaneous use of atorvastatin in a dose of 40 mg and itraconazole at a dose of 200 mg 1 time / day, there was an increase AUC up to a value exceeding that of monotherapy in 3 times.
With the simultaneous use of atorvastatin (10 mg 1 time / day) and azithromycin (500 mg 1 time / day), the concentration of atorvastatin in plasma did not change.
Simultaneous use of atorvastatin with inhibitors of proteases, which are inhibitors of the isoenzyme CYP3A4, was accompanied by an increase in the concentration of atorvastatin in blood plasma.
Effects of drugs that induce isoenzyme CYP3A4 (for example, rifampicin and phenazone), on atorvastatin is unknown. The interaction with atorvastatin and other substrates of this isoenzyme is not known, but the possibility of such interaction should be taken into account when using drugs with a low therapeutic index, in particular, class III antiarrhythmics, for example, amiodarone.
The risk of myopathy caused by atorvastatin may increase with the concomitant use of fibrates. Research m vitro suggest that gemfibrozil can also interact with atorvastatin by inhibiting its glucuronation, which can cause an increase in atorvastatin concentrations in the plasma. With repeated administration of digoxin and atorvastatin at a dose of 10 mg, the equilibrium concentrations of digoxin in the blood plasma did not change. However, when using digoxin in combination with atorvastatin at a dose of 80 mg / day, the digoxin concentration increased by about 20%. Patients receiving digoxin simultaneously with atorvastatin, should be observed. Taking atorvastatin concomitantly with an oral contraceptive containing norethisterone and ethinyl estradiol, caused an increase in the concentrations of norethisterone and ethinyl estradiol in plasma. These increases in concentration should be considered when choosing doses of oral contraceptives. With the simultaneous use of atorvastatin and a contraceptive for oral administration containing norethisterone and ethinyl estradiol, there was a significant increase AUC norethisterone and ethinyl estradiol by approximately 30% and 20%, respectively. This effect should be considered when choosing an oral contraceptive for a woman receiving atorvastatin.
With the introduction of colestipol in combination with atorvastatin, there was a decrease in the concentration of atorvastatin in the blood plasma by approximately 25%. However, with the combined use of atorvastatin and colestipol, the effect on lipids was more pronounced than with each of these drugs alone.
With simultaneous ingestion of atorvastatin and a suspension containing magnesium and aluminum hydroxide, the concentration of atorvastatin in blood plasma decreased by about 35 %; however, the degree of decrease in LDL-C level did not change at the same time.
When taking atorvastatin in combination with warfarin, there was a slight decrease in prothrombin time in the first days of atorvastatin administration; but in the next 15 days the prothrombin time returned to normal. However, in the case of simultaneous use of atorvastatin and warfarin, patients should be carefully monitored.
With simultaneous application atorvastatin does not affect the pharmacokinetics of phenazone, therefore interaction with other agents metabolized by the same cytochrome isoenzymes is not expected.
The study of simultaneous administration of cimetidine and atorvastatin did not reveal a significant interaction between these drugs.
With the simultaneous administration of atorvastatin in a dose of 80 mg and amlodipine at a dose of 10 mg, there was no change in the pharmacokinetic parameters of atorvastatin in the equilibrium state.
There was no clinically significant undesirable interaction of atorvastatin and antihypertensive agents. Studies of interaction with all specific drugs have not been conducted.
Atorvastatin had no clinically significant effect on the concentration of terfenadine in the blood plasma, which is metabolized mainly by isoenzyme CYP3A4; in this connection it seems unlikely that atorvastatin can significantly affect the pharmacokinetic parameters of other isoenzyme substrates CYP3A4.
With the simultaneous administration of atorvastatin at a dose of 80 mg per day and amlodipine at a dose of 10 mg, the pharmacokinetics of atorvastatin did not change in the equilibrium state.
Simultaneous administration of atorvastatin at a dose of 40 mg per day and diltiazem in a dose of 240 mg leads to an increase in the concentration of atorvastatin in the blood plasma.
Grapefruit juice contains at least one ingredient that is an inhibitor CYP3A4, and can cause an increase in plasma concentrations of those drugs that are metabolized CYP3A4. At a daily intake of 240 ml of grapefruit juice, there was an increase AUC atorvastatin by 37% and decrease AUC active orthohydroxy metabolite by 20.4%. When consuming a large amount grapefruit juice (more than 1.2 liters per day for 5 days) value AUC atorvastatin increased by 2.5 times, a AUC active inhibitors of HMG-CoA reductase (atorvastatin and its metabolites) - 1.3 times. In this regard, the consumption of large quantities of grapefruit juice during treatment with atorvastatin is not recommended.