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Keith I Block

Publications and source records attributed to Keith I Block.

50 records · Page 3Linked to original sources
PubMed2003

Immune system effects of echinacea, ginseng, and astragalus: a review.

Traditional herbal medicine provides several remedies for strengthening the body's resistance to illness through effects on immune system components. This review article examines 3 popular herbal immune stimulants that are often of interest to cancer patients. Echinacea, a native of North America, is widely used to prevent, or provide early treatment for, colds. Preclinical studies lend biological plausibility to the idea that echinacea works through immune mechanisms. Numerous clinical trials have been carried out on echinacea preparations: it appears that the extracts shorten the duration and severity of colds and other upper respiratory infections (URIs) when given as soon as symptoms become evident. However, trials of long-term use of echinacea as a preventive have not shown positive results. Ginseng has been studied in some depth as an antifatigue agent, but studies of immune mechanisms have not proceeded so far. Preclinical evidence shows some immune-stimulating activity. There have been several clinical trials in a variety of different diseases. Astragalus is the least-studied agent. There are some preclinical trials that show intriguing immune activity. The herbs discussed appear to have satisfactory safety profiles. Cancer patients may wish to use these botanicals to inhibit tumor growth or to boost resistance to infections. However, passive immunotherapy with herbs, with no mechanism to expose tumor antigens, is unlikely to be effective in inhibiting tumor growth. Although the margin of safety for these herbs is large, more research is needed to demonstrate the clear value of using herbs to improve resistance to infections.

Adjuvants, Immunologic↗
PubMed2002

Chronomodulated chemotherapy: clinical value and possibilities for dissemination in the United States.

Modern medicine has been relatively slow to apply chronotherapeutic principles to standard oncologic practice. Despite the impressive body of evidence supporting the use of chronochemotherapy, with only a rare exception most oncology clinics in the United States lack the expertise and capability to implement it. At the same time, American medicine has increasingly come to recognize the importance of toxicity mitigation, cytoprotection, and quality of life for patients undergoing cancer treatment. However, toxicity mitigation strategies such as chronomodulated infusional chemotherapy and novel cytoprotective agents are not widely embraced by U.S. physicians. This article explores some reasons why this situation exists, including the influence of non-medical biases that may affect management decisions on the application of chemotherapy. The author conducted a survey of U.S. companies representing the three private insurance payers available (HMO, PPO, Indemnity) as well as representatives of Medicare and Medicaid. Responses to the survey confirmed that U.S. insurers do not at present officially reimburse for chronotherapy; however, changes will come about through educational efforts aimed at increasing awareness among insurers as to the clinical benefits and cost-effectiveness of this mode of treatment. At this juncture, the outlook for cancer chronotherapy as a first-line approach to the treatment of metastatic cancer in the United States remains uncertain. Under the current method of insurance reimbursement, the advancement of chronotherapy in the United States is threatened despite evidence that such treatment is both therapeutically sound and cost-effective.

Antineoplastic Agents↗
PubMed2002

Clinical corner: herb-drug interactions in cancer chemotherapy: theoretical concerns regarding drug metabolizing enzymes.

Interactions between herbal medicines and conventional drugs have recently been reported; the most significant herb with such drug interactions is Saint John's wort, an inducer of cytochrome P450 3A3/4, an enzyme responsible for clearance of many clinically important drugs from the body. Foods (especially grapefruit) and habits or lifestyle factors such as smoking or alcohol consumption may also alter the metabolism of drugs through effects on the cytochrome P450 system. The authors review here the functioning of the drug-metabolizing enzymes and discuss their particular significance in cancer chemotherapy treatment. They then present the herbal medicines, foods, and lifestyle factors that induce or inhibit drug-metabolizing enzymes that are important for both cancer chemotherapy drugs and drugs used adjunctively in cancer treatment. It is notable that no actual herb-drug interactions have been reported clinically in cancer treatment, and their potential for interaction still must be regarded as theoretical. Although some chemotherapy patients may be interested in taking herbal medicines that could potentially interact with cancer chemotherapy agents, it may be wise to counsel them to use other means of addressing the problems for which they use specific herbs during the time they receive chemotherapy.

Cytochrome P-450 Enzyme System↗