A recent discussion on the excellent PozHealth listserve has alerted us to a potential problem with the relatively new HIV medication, raltegravir (brand name, Isentress). This drug inhibits an enzyme used by HIV called integrase.
As with many medications, it needs to be absorbed properly by the body after being taken. Some drugs can interact with this, blunting its benefit in lowering viral load to undetectable. In particular, antacids (that often come in the form of calcium carbonate) appear to reduce the drug’s efficacy when they are taken at the same time.
One contributor to the list noted that he now takes the drugs separately from any antacids as WELL as his K-PAX. This is prudent. We strongly urge you to separate any multi or other minerals that may inhibit the benefit of this medication by taking them about 4 hours apart.
This is also based on some research, as discussed on the HIV Insite website. They note: “: ”It appears that polyvalent cations (such as magnesium, calcium, and iron) bind integrase inhibitors and interfere with their activity against integrase. A pharmacokinetic study showed that administration of antacids containing divalent cations at the same time as elvitegravir (an investigational integrase inhibitor) lowered serum elvitegravir concentration by more than 40%. This effect was minimal if antacids were taken 4 hours apart from the integrase inhibitor.(5) The interaction of raltegravir and antacids has not been studied; pending further investigation, antacid medications and other agents with polyvalent cations should be used cautiously with (and taken separately from) raltegravir.”
(If you would like to join the POZHealth group, send a blank email to PozHealthfirstname.lastname@example.org and you will get an email with instructions to follow. It is a terrific group!)