Calcium channel blockers and cancer: is there preclinical evidence for an association?

Update of carcinogenicity studies in animals and humans of 535 marketed pharmaceuticals

This survey is a compendium of information retrieved on carcinogenicity in animals and humans of 535 marketed pharmaceuticals whose expected clinical use is continuous for at least 6 months or intermittent over an extended period of time. Of the 535 drugs, 530 have the result of at least one carcinogenicity assay in animals, and 279 (52.1%) of them gave a positive response in at least one assay. Only 186 drugs (34.8%) have retrievable information on carcinogenicity in humans, and 104 of them gave to a variable extent evidence of a potential carcinogenic activity. Concerning the correlation between results obtained in animals and epidemiological findings, 58 drugs gave at least one positive result in carcinogenicity assays performed in animals and to a variable extent displayed evidence of carcinogenicity in humans, but 97 drugs tested positive in animals and were noncarcinogenic in humans or vice versa. Our findings, which are in agreement with previous studies, indicate that the evaluation of the benefit/carcinogenic risk ratio should be always made in prescribing a drug.

High-altitude medicines: A short-term genotoxicity study

People live in the mountains distributed across the world and are exposed to reduced inspired oxygen and lower barometric pressure along with other factors that lead to high-altitude diseases. The present study was conducted to examine what extent of marketed medicines used in the management of high-altitude sickness has been tested for their genotoxic activity. Comet assay or the single-cell gel electrophoresis was utilized to evaluate genotoxicity of the six medicines on human peripheral whole blood cells and isolated lymphocytes at the concentrations 250 μg/mL, 500 μg/mL and 1 mg/mL. The comet assay endpoints included percentage Tail DNA (% Tail DNA) and olive tail moment (OTM) as they were considered to be sensitive and reliable scores across different laboratories. The results show that dexamethasone, deriphylline and furosemide can induce significant DNA damage in human whole blood and lymphocytes alike. Acetazolamide, ibuprofen and nifedipine show no genotoxic effect, neither on human whole blood nor on human lymphocytes. Taking into account the results of genotoxicity, it will be a prudent choice to restrict the use of these compounds for longer periods, until more information on the in vitro mutagenicity and in vivo genotoxicity studies are available.

Adverse and beneficial effects of tocolytic therapy

In addition to questions raised about the efficacy of many tocolytics, appropriate concern has been voiced about the safety of these potent drugs. Although some degree of risk for adverse effects with drugs promising a strong therapeutic effect can be accepted, caution needs to be exercised when benefits are marginal or unproven. Unfortunately, some of the tocolytics, most notably the betamimetics and magnesium sulfate, have been found to have considerable potential for adverse maternal cardiovascular and respiratory effects. Although less clearly established, the use of indomethacin appears to be associated with increased fetal and neonatal risks. Concerning magnesium sulfate, in addition to the well-known maternal effects, the accumulating evidence showing an increased frequency of adverse outcomes in the fetus and neonate has led to the recommendations to abandon its use entirely as a tocolytic. Given the limitations of our current state of knowledge, nifedipine would appear to be among the more efficacious and safer tocolytics available to use when properly indicated.

Calcium channel blockers in the management of preterm labor and hypertension in pregnancy

Calcium channel blockers (CCBs) have the ability to inhibit contractility in smooth muscle cells. CCBs have an already established role in the treatment of non-pregnant hypertension and angina pectoris. Some epidemiological studies found an association between the use of CCBs and an increase in cardiovascular mortality, malignancy, and gastrointestinal bleeding. More recent studies with many more patients and a longer follow-up did not find these associations. In obstetrics CCBs have become increasingly popular for the management of preterm labor and pregnancy-induced hypertensive disorders. Meta-analysis shows that use of nifedipine in comparison with betamimetics is associated with a more frequent successful prolongation of pregnancy in case of preterm labor, resulting in significantly fewer admissions of newborns to the neonatal intensive care unit (NICU), and is associated with a lower incidence of respiratory distress syndrome. No adverse fetal side effects in humans have been reported with the use of nifedipine for obstetric indications. Nifedipine is an effective and safe drug to use when tocolytic therapy is indicated for preterm labor. In preeclampsia nifedipine effectively lowers blood pressure and can be a good alternative for (di) hydralazine.

Calcium channel blockers, apoptosis and cancer: is there a biologic relationship?

Calcium channel blockers (CCBs) represent a chemically and pharmacologically diverse group of agents that are widely used for the treatment of hypertension and angina. A small number of retrospective, observational analyses have raised concern about a potential causal link between CCB use and an increased risk for cancer development. Despite the absence of cancer findings in extensive preclinical studies, it has been proposed that CCBs may work differently in humans by interfering with apoptosis, leading to an increased potential for abnormal cell proliferation and tumor growth. This biologic hypothesis has attracted considerable attention in the medical community but has not been critically evaluated. An analysis of the basic and clinical literature was conducted to examine biologic relationships among cell Ca2+ modulation, apoptosis, and cancer. In addition to a comprehensive review of the cellular and animal data, the results of large observational studies were included in this analysis. Results of this review demonstrated that the effects of CCBs on apoptosis are complex as both increases and decreases in intracellular Ca2+ have been linked to this form of programmed cell death. Most studies show that an effect (either positive or negative) of CCBs on apoptosis requires doses in the supra-pharmacologic range, and are therefore not clinically relevant. Results of large and methodologically robust observational studies fail to provide support for the hypothesis that CCB use is associated with an increased susceptibility for cancer incidence. A comprehensive analysis of the basic and clinical evidence does not support a causal relationship between the therapeutic use of CCBs and an increased incidence of cancer development as a result of interfering with apoptosis.

Effects of calcium channel blockers on cellular apoptosis: implications for carcinogenic potential

BACKGROUND

A small number of well-publicized, retrospective epidemiologic reports have suggested a causal relation between the use of calcium channel blockers (CCBs) for the treatment of hypertension and an increased risk for cancer. The biologic mechanism proposed to explain this possible relation is that CCBs interfere with apoptosis, an active cell death process required for the regulation of normal cell populations in the body. Because an elevation in cellular calcium (Ca2+) is thought to be involved in apoptosis, it has been argued that CCBs could inhibit apoptosis, leading directly to tumor promotion.

METHODS

A comprehensive and critical review of the scientific literature was conducted specifically to evaluate the effects of pharmacologic CCBs on apoptosis and tumor development in various experimental models.

RESULTS

A review of the scientific literature revealed that CCBs have complex and often contradictory effects on cellular apoptosis. In various experimental models of cancer, CCBs did not promote neoplastic growth. By contrast, CCB treatment was associated with an inhibition of tumor growth in certain models of neoplasia and was also an effective adjuvant therapy in the treatment of certain drug-resistant tumors. Additional large epidemiologic studies have failed to support the hypothesis that CCB use is associated with an increased susceptibility for cancer.

CONCLUSIONS

A biologic link between the use of CCBs and increased human risk for cancer development as a result of modulating cellular apoptosis is not supported by the scientific literature.