Antihistamines meclizine

Ar)me et al. [26] presented rapid liquid chromatographic procedures for quality control of pharmaceuticals and human serum containing antihistamines, meclizine, and buclizine alone or in combination with pyri-doxine using acetonitrile water (80 20) as a mobile phase (pH adjusted to 2.6), methylparaben as internal standard deviation and UV detection was made at 230 nm. The results obtained showed a good agreement with the declared content. The method had good linearity in the range of 0.03-10 pg/ml for pyridoxine and (0.025-10 pg/ml) for meclizine and buclizine serum concentration with a correlation coefficient of 0.9999. 

The nausea and vomiting associated with the first trimester of pregnancy are benign and self-limiting in nature. If at all possible, no medications should be used. If absolutely necessary, antihistaminics (meclizine and trimethobenzamide) may be effective. Pyridoxine (vitamin Bg) should not be prescribed, as it may predispose the infant to vitamin Bg-dependent syndrome. 

Some antihistamines such as diphenhydramine, dimenhy-drinate, and meclizine are available without a prescription, making self-treatment convenient for patients. Antihistamines are available in a variety of dosage forms, including oral capsules, tablets and liquids. Liquid formulations are convenient for children or adults who are unable to swallow solid dosage forms. 

Antagonists. Most of the so-called Hi-antihistamines also block other receptors, including M-cholinoceptors and D-receptors. Hi-antihistamines are used for the symptomatic relief of allergies (e.g., bamipine, chlorpheniramine, clemastine, dimethindene, mebhydroline pheniramine) as antiemetics (meclizine, dimenhydrinate, p. 330), as over-the-counter hypnotics (e.g., diphenhydramine, p. 222). Promethazine represents the transition to the neuroleptic phenothiazines (p. 236). Unwanted effects of most Hi-antihistamines are lassitude (impaired driving skills) and atropine-like reactions (e.g., dry mouth, constipation). At the usual therapeutic doses, astemizole, cetrizine, fexofenadine, and loratidine are practically devoid of sedative and anticholinergic effects. Hj-antihistamines (cimetidine, ranitidine, famotidine, nizatidine) inhibit gastric acid secretion, and thus are useful in the treatment of peptic ulcers. 

Motion sickness. Effective prophylaxis can be achieved with the parasympatholytic scopolamine (p. 106) and H antihistamines (p. 114) of the diphenyl-methane type (e.g., diphenhydramine, meclizine). Antiemetic activity is not a property shared by all parasympatho-lytics or antihistamines. The efficacy of the drugs mentioned depends on the actual situation of the in vidual (gastric filling, ethanol consumption), environ-... 

Pharmacoiogy Cyclizine and meclizine have antiemetic, anticholinergic, and antihistaminic properties. 

Another important use of Hj-antagonists is in the treatment of motion sickness. Diphenhydramine (Benadryl), dimenhydrinate (Dramamine), cyclizine (Marezine), and meclizine (Antivert) have anticholinergic activity and are the preferred antihistaminic agents for reducing the symptoms of motion sickness. 

H -antagonists are well absorbed from the gastrointestinal tract. Following oral administration, antihistaminic effect is manifested within 30 minutes, peak plasma concentration is achieved in 2 to 3 hours and effects usually last 4 to 6 hours. However, drugs in piperazine subgroups especially chlorcyclizine and meclizine, the actions persists for 8 to 12 and 12 to 24 hours respectively. 

Clinically important, potentially hazardous interactions with antihistamines, azatadine, brompheniramine, buclizine, chlorpheniramine, clemastine, dexchlorpheniramine, diphenhydramine, meclizine, tripelennamine... 

The most common side effect of the antihistaminics is sedation, and all of them cause it to varying degrees. For example, diphenhydramine, dimenhydrinate, and promethazine cause marked sedation, but pyrilamine produces only moderate sedation. Chlorpheniramine, meclizine, and cyclizine have mild sedative properties, while terfenadine, astemizole, loratadine, and cetirizine are nonsedating. 

Meclizine (25 to 50 mg 1 hour prior to travel) is indicated in prevention and treatment of nausea, vomiting, and dizziness of motion sickness. Meclizine has antiemetic, anticholinergic, and antihistaminic properties. It reduces the sensitivity of the labyrinthine apparatus. The action may be mediated through neuronal pathways to the vomiting center (VC), from the chemoreceptor trigger zone (CTZ), peripheral nerve pathways, or other CNS centers (see also Figure 73). 

SAR of Meclizine. It apparantly differs from chlorcyclizine by possessing anN- 7-methylben2yl functional moiety instead of the prevailing N-methyl moiety. Thus, it exhibits moderately potent antihistaminic profile. 

Introduetion of basic-cyclic ring system by altering the position of dimethyl amino group also enhances the antihistaminic activity, e.g., cyclizine, chlorcyclizine, meclizine etc. 

Anticholinergics/ Antihistamines Diphenhydramine, dimenhydrinate and meclizine are antihistamines with anticholinergic effects. Anticholinergic drugs reduce motion sickness as well as emesis. 

Diarylmethylene groups (benzhydryl substituents, as in diphenhydramine) are attached to one of the nitrogen atoms, and an alkyl or aralkyl substituent is attached to the other nitrogen. Early compounds, such as cyclizine, chlorcyclizine, meclizine, buclizine, and hydroxyzine, have been widely used as antihistamines and as agents for treatment of motion sickness, because they have useful central antiemetic effects. 

Newton DW, Murray W] and Lovell MW, pKg determination of benzhydrylpiperazine antihistamines in aqueous and aqueous methanol solutions, /. Pharm. Set, 71(12), 1363-1366 (1982). NB Attempted to measure pKa for meclizine by extrapolation of apparent pKa values in cosolvent-water mixtures to 0% cosolvent, but found diat meclizine could only be titrated in >47.8% methanol solutions, which was too hi. ... 

Antihistamine antiemetics such as diphenhydiinate (Dramamine), meclizine hydrochloride (Antivert), and diphenhydramine hydrochloride (Benadryl) are over-the-counter medications that prevent nausea, vomiting, and dizziness (vertigo) caused by motion by inhibiting stimulation in the middle ear. They also cause drowsiness, dryness of the mouth, and constipation. 

The client is prescribed meclizine (Antivert), an antihistamine, for vertigo. Which statement by the client would warrant intervention by the nurse ... 

Tranquilizers (e.g., meprobamate, chlorproraazine, reserpine, diazepam) Antihistamines (e.g., buclizine, meclizine, cyclizine)... 

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