Biaxin made its debut in the myeloma world in the early '90s, when thalidomide was the only "novel therapy."  Doctors noticed that patients who were receiving Biaxin treatment for an infection (or to prevent infection) while they were being treated with thalidomide and dex responded better to treatment than those who were receiving thalidomide and dex but not Biaxin.  Researchers concluded that the synergy between thalidomide, Biaxin, and dexamethasone was responsible for the improved response rate.  Biaxin made the so-called "thal/dex" regimen more effective.  A recent phase II Mayo Clinic study of Biaxin + Revlimid + low-dose dexamethasone  vsersus Revlimid + low-dose dexamethason alone in patients with newly diagnosed myeloma [Gay et al, Am. J Hematol. 2010 Sep;85(9):664-9] demonstrated that "there is significant additive value when clarithromycin is added to Rd."  A phase III trial is planned to confirm these results. 

In fact, Biaxin interacts with many other drugs, not just those used to treat myeloma.  The National Center for Biotechnology Information (NCBI), part of the National Institutes of Health, has a large compendium of information on drugs.  In their entry for clarithromycin, there is a long list of drugs with which clarithromycin has interactions.  Patients are cautioned to:

• Tell your doctor if you are taking astemizole (Hismanal) (not available in the U.S.), cisapride (Propulsid), dihydroergotamine (DHE 45, Migranal), ergotamine (Ergomar, in Cafergot, in Migergot), pimozide (Orap), or terfenadine (Seldane) (not available in the U.S.). Your doctor may tell you not to take clarithromycin if you are taking one or more of these medications.
• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. 
• Be sure to mention any of the following: anticoagulants ('blood thinners') such as Warfarin (Coumadin); alfentanil (Alfenta); alprazolam (Xanax); bromocriptine (Parlodel); carbamazepine (Tegretol); cholesterol-lowering medications such as lovastatin (Mevacor), simvastatin (Zocor), or atorvastatin (Lipitor); cilostazol (Pletal); colchicine; cyclosporine (Neoral, Sandimmune); darifenacin (Enablex); digoxin (Lanoxin); erlotinib (Tarceva); eszopiclone (Lunesta); fluconazole (Diflucan); certain medications for HIV such as nelfinavir (Viracept), ritonavir (Norvir), and zidovudine (AZT, Retrovir); certain medications for irregular heartbeat such as disopyramide (Norpace) and quinidine; methylprednisolone (Medrol), midazolam (Versed); omeprazole (Prilosec); phenytoin (Dilantin); ranitidine (Zantac); rifabutin (Mycobutin); rifampin (Rifadin, Rimactane); sildenafil (Viagra), tacrolimus (Prograf); theophylline (Theo-Dur); triazolam (Halcion); valproate (Depacon) and valproic acid (Depakote). 

Many other medications may also interact with clarithromycin, so tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.

This information about Biaxin is important in its own right, for those of you who are taking it, but should also serve as a warning about drugs in general.  MANY DRUGS CAUSE UNDESIRED OR UNANTICIPATED INTERACTIONS WHEN THEY ARE COMBINED.  

You should make it a practice to have your pharmacist check on drug-drug interactions no matter which medications you're taking, and no matter which days of the week or which times of day you take them. They don't have to be literally taken in combination.  This includes vitamins and supplements, not just prescription drugs.  

There is computer software available to pharmacists so that they can perform due diligence and prevent you from having problems with drug interactions.   Present you pharmacist with a complete list of all medications, vitamins, and supplements that you're taking.  This is part of being a good patient-  just ask blogger Mike Katz, The Good Patient.