Drug Interactions

  • Can I use antacids to help with heartburn and other stomach issues?

    Many people occasionally use an antacid or other over the counter medication for symptoms like heartburn, indigestion, gas or bloating. The majority of these medications can decrease the amount of a tyrosine kinase inhibitor (TKI) that your body can easily absorb.

    ANTACIDS Antacids can reduce the amount of TKI (its bioavailability) that your body receives if taken too close in time to your TKI dose. The data from studies with dasatinib show that its absorption and solubility are affected by changes in pH. Antacids change the pH of the gastrointestinal environment. When dasatinib was given to 24 patients two hours after a dose of over-the-counter antacid (aluminum hydroxide), there was no relevant change in the dasatinib levels. However, when dasatinib was given at the same time as an over-the-counter antacid, the dasatinib level was significantly decreased. There have not been clinical trials with nilotinib evaluating the effects of antacid use. However, nilotinib is dependent on pH for solubility and would therefore, be effected by antacid use.  Antacids may be used up to two hours before and two hours after a dose of dasatinib. Examples include Tums, Rolaids and Maalox.

    PROTON PUMP INHIBITORS AND H2 ANTAGONISTS  Medications in these categories also change the pH of the body's gastrointestinal environment, reducing the dose of TKI that your body is able to absorb. These drugs are particularly problematic because they tend to have much longer effects than the antacids discussed above. When 24 patients were administered dasatinib 10 hours after receiving famotidine, the patients dasatinib levels (bioavailability per AUC) were reduced by over 60%. When patients received bosutinib along with doses of lansoprazole, the bioavailability of bosutinb was decreased.  Examples of these medications, which should not be used with TKIs, include: Pepcid, Zantac, Tagamet, Prilosec, Protonix, Nexium, and Prevacid.

  • Why does my CML specialist watch my thyroid function each visit?

    Conditions involving the thyroid can be complex and difficult to diagnose, and much more so in individuals living with a cancer diagnosis. There is increasing evidence of changes in thyroid function related to treatment with tyrosine kinase inhibitors.

    As more experience with tyrosine kinase inhibitors (TKIs) is documented through clinical trials and wider patient experience, there is increased focus on the effects of TKIs on the thyroid. With first generation TKIs used for cancers other than CML, there have been reports of changes in thyroid function in up to and over fifty percent of patients. There is significant experience with patients with renal cell carcinoma and with gastrointestinal stromal tumors. (See http://www.gistsupport.org/ask-the-professional/thyroid-damage-from-tyrosine-kinase-inhibitors.php and http://www.ncbi.nlm.nih.gov/pubmed/19333228)

    More recently, investigators have been looking into the relationship of second generation TKIs, to thyroid dysfunction. In one German study, 45% of patients taking a second generation TKI experienced thyroid changes, including hypothyroidism and hyperthyroidism and other thyroid conditions. (Reference http://www.ncbi.nlm.nih.gov/pubmed/20929406)
    In a study done by investigators at Harvard Medical School and published in 2011, the thyroid was affected by a number of the newer anti-cancer drugs, including the targeted therapies and TKIs needed by individuals living with CML.

    The results of this study led to recommendations for routine thyroid testing in all patients taking targeted therapies including TKIs. It is important to note that although the most frequent thyroid related adverse effect is a decrease in thyroid function (hypothyroidism), other thyroid conditions can also be present and should be assessed frequently in the first year of therapy. Changes in function can happen as early as six weeks after beginning TKI therapy.

    The treatment for hypothyroidism includes the oral administration of levothyroxine (Synthroid) on a daily basis. Patients appear to tolerate this well, although frequent laboratory testing may be necessary to regulate the dose of Synthroid in the period immediately following the initiation of therapy. Check with your CML team to find the results of your laboratory tests for thyroid function. Look for a pattern of increasing or decreasing levels of thyroid stimulating hormone (TSH). TSH will usually be elevated in cases of decreased thyroid function or hypothyroidism. Use a CML tracking system to record your laboratory results from this test and others related to your CML and overall health.