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To: Nancy Walker As regards the use of beta-blockers and antihistamines, it is not clear what you mean by RfightingS each other. There are two types of antihistamines: H1-blockers and H2-blockers. H1-blockers generally can be thought of as two types: the older ones (first generation) and the newer ones (second generation). The older ones such as chlorpheniramine, brompheniramine, diphenhydramine, tripelennamine, hydroxyzine, cetirazine, meclizine, and many others, tend to be sedating. The second generation or newer ones such as astemizole (Hismanal), loratadine (Claritin), and terfenadine (Seldane) tend not to be sedating. H2-blockers include some of the medications which decrease acid production in the stomach such as cimetidine, famotidine, nizatidine, and ranitidine (others such as omeprazole (Losec) are not H2-blockers). Other drugs have antihistamine properties, but are usually classified according to their major effect. For example, the phenothiazines such as chlorpromazine have antihistamine effects, but are usually called major tranquillizers or antipsychotic drugs, not antihistamines. Beta-blockers also can be divided into subtypes according to their effect on the cardiovascular system, their effect on the central nervous system (how fat soluble they are determines to a large extent how readily they cross into the brain), their effect in controlling (or causing) some types of abnormal heart rhythms, and their undesirable effect on other tissues such as the lungs (some types are more likely to cause asthma in people prone to asthma). If you are on a Beta-blocker, can you take an antihistamine? It probably depends on the type of Beta-blocker you are on, the reason for being on it, other diseases you might have or are prone to, and the type of antihistamine you wish to take. There are no reports of any interactions between H1-blocker type antihistamines and beta-blockers in the standard books having lists of drugs, and at least the older types can be used relatively safely with beta-blockers. However, there is a report on a beta-blocker called Sotalol (Sotacor) in the Handbook of Adverse Drug Interactions: RSotalol has the usual adverse effects of a beta-blocker, most commonly fatigue, bradycardia, and dyspnea, and also can have a proarrhythmic effect [can cause the heart to beat irregularly]; it causes torsades de pointes, a serious ventricular arrhythmia [which can lead to death], in 3% to 5% of patients, particularly those who have prolonged QTc intervals. Additive effects are likely with other drugs that prolong the QTc interval, including the antihistamines terfenadine (Seldane) and astemizole (Hismanal), phenothiazines, and tricyclic antidepressants.S There are a few reports of interactions between beta-blockers and H2-blocker type antihistamines. Ranitidine and high doses of Cimetidine possibly may cause beta-blocker toxicity. Antihistamines with anticholinergic properties may be helpful in reducing rigidity in PD, but tend not to have as much effect on tremor as other types of anticholinergic drugs. Diphenhydramine (Benadryl), and Chlorpheniramine are two examples. Other drugs with antihistamine properties, and anticholinergic properties have been used as well. For example, Ethopropazine (Parsidol, Parsitan), usually classified as a phenothiazine or major tranquilliser but which has antihistamine and anticholinergic properties, is approved as an antiparkinsonian agent. It is not commonly used however, probably because of the concern about the potential side effects of this class of drugs such as dyskinesias. I believe your doctor probably told you to avoid beta-blocker type drugs because if you are on them, they might precipitate asthma. Additionally, if you were on a beta-blocker, and had a bad allergic reaction, the beta-blocker could block the effects of some of the main drugs such as epinephrine (adrenalin) used to treat severe allergic reactions. Brian Symonds <[log in to unmask]>