CSM issues safety update on grapefruit and statins
Grapefruit juice should be avoided in patients taking simvastatin |
Updated advice on the risks of drinking grapefruit juice while taking
statins, issued by the Committee on Safety of Medicines and the Medicines
and Healthcare products Regulatory Agency, and guidance on the risk of
venous thromboembolism when taking oral contraceptives, are published
in the latest issue (PDF 75K) of Current Problems in Pharmacovigilance (2004:30).
The bulletin says that recent pharmacokinetic evidence suggests that
grapefruit juice should be avoided altogether when taking simvastatin,
because even modest quantities of the drink can increase exposure to
the drug. The bulletin includes a summary of advice for prescribing simvastatin
together with other CYP3A4 inhibitors.
For atorvastatin (Lipitor), it says that caution should be exercised
when combining it with any CYP3A4 inhibitor, and that patients taking
it should avoid drinking large quantities of grapefruit juice. However,
fluvastatin (Lescol) is metabolised by a different enzyme and pravastatin
(Lipostat) and rosuvastatin (Crestor) are not substantially metabolised
by cytochrome P450.
Regarding rosuvastatin, the bulletin emphasises that all patients must
start on 10mg once daily and should only be titrated to 20mg if this
is considered necessary after a four-week trial of 10mg. The 40mg dose
is contraindicated in patients with predisposing risk factors for muscle
toxicity and specialist supervision is recommended when this dose is
initiated.
Turning to combined oral contraceptives, the bulletin says that although
previous data have suggested that there might be a high rate of venous
thromboembolism (VTE) in Yasmin (drospirenone/ethinylestradiol) users,
interim data from a large cohort study suggest that the VTE rate is comparable
to that for users of other combined oral contraceptives. It reminds readers
that all combined oral contraceptives increase the risk of VTE, and that
they should be prescribed with caution for obese women and those with
a higher baseline risk.
Other advice in the bulletin is that patients taking warfarin should
avoid consuming cranberry juice or other cranberry products unless the
health benefits are considered to outweigh any risks, and that monitoring
anti-factor-Xa activity may be helpful for patients being treated with
low molecular weight heparins who are at risk of bleeding. The bulletin
also contains reminders about the prescribing advice for paroxetine,
the contraindications of thiazolidinediones (glitazones), flucloxacillin
and serious hepatic disorders and the safety of traditional Chinese medicines
and herbal remedies.
The bulletin can be accessed here |
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