Halothane agonists

Drugs that may interact with labetalol include beta-adrenergic agonists, cimetidine, glutethimide, halothane, and nitroglycerin. 

The following agents may be affected by theophylline Benzodiazepines, -agonists, halothane, ketamine, lithium, nondepolarizing muscle relaxants, propofol, ranitidine, and tetracyclines. Probenecid may increase the effects of dyphylline. 

A clinically useful action of a2-agonists is their ability to reduce the requirements for other anaesthetic agents during anaesthesia. In control mice, non-sedative doses of dexmedetomidine reduced the concentrations of the volatile anaesthetic, halothane, to induce anaesthesia by 30% (Lakhlani et al. 1997). This anaesthetic-sparing effect of a2-agonists was completely abolished in a2A-D79N mice. 

Metaproterenol (Alupent, Metaprel) [Bronchodilator/ Beta-Adrenergic Agonist] Uses Asthma reversible bronchospasm Action Sympathomimetic bronchodilator Dose Adults. Neb 0.2-0.3 mL in 2.5-3.0 mL of NS Peds. Neb 0.1-0.2 mL/kg of a 5% soln in 2.5 mL NS Caution [C, /-] Contra Tach, other arrhythmias Disp Aerosol 0.65 mg/inhal soln for inhal 0.4, 0.6% tabs 10, 20 mg syrup 10 mg/5 mL SE Nervousness, tremors (common), tach, HTN Interactions T Effects W/ sympathomimetic drugs, xanthines T risk of arrhythmias W/ cardiac glycosides, halothane, levodopa, theophylline, thyroid hormones T HTN W/ MAOIs effects W/ BBs EMS Separate additional aerosol use by 5 min fewer 3i effects than isoproterenol longer-acting monitor lung sounds before/after administration... 

The effect of the sympathomimetic drugs on the pregnant uterus is Vciriable and difficult to predict, but serious fetal distress can occur, due to reduced placental blood flow as a result both of contraction of the uterine muscle (a) and arterial constriction (a). Pj-agonists are used to relax the uterus in premature labour, but unwanted cardiovascular actions can be troublesome. Sympathomimetics were particularly likely to cause cardiac arrhythmias (p, effect) in patients who received halothane anaesthesia (now much less used). 

Hug C G (eds) Pharmacokinetics of anaesthesia. Blackwell, Boston, MA, p. 157 Riedesel D H, Hildebrand S V 1985 Unusual response following use of succinylcholine in a horse anesthetized with halothane. Journal of the American Veterinary Medical Association 187 507-508 Robertson S A, Carter S W, Donovan M et al 1990 Effects of intravenous xylazine hydrochloride on blood glucose, plasma insulin and rectal temperature In neonatal foals. Equine Veterinary Journai 22 43-47 Roger T, Bardon T, Ruckebush Y 1994 Comparative effects of mu and kappa opiate agonists on the cecocolic motility In the pony. Canadian Journal of Veterinary Research 58 163-166... 

X 0 X 1 s CQ (d PO/IM/IV. Well aosorbed, high first pass metabolism, metabolized in liver. Dose adjustment unnecessary w/renal-liver dysfunction. Contraindicated in patients with asthma or bradycardia. Myocardial depression w/halothane. Blocks 6-agonist induced bronchodilation. ... 

Halothane is known to cause arrhythmias and it has been suggested that it may increase susceptibility to the adverse cardiac effect of beta-agonist bronchodilators, which can cause arrhythmias. Note that beta agonists such as terbutaline are sympathomimetics (see Table 24.1 , (p.879)), like adrenaline (epinephrine), which has also been shown to cause arrhythmias in the presence of halothane (see Anaesthetics, general + Inotropes and Vasopressors , p.99). 

Phenylephrine is a sympathomimetic, and as such may carry some risk of potentiating arrhythmias if it is used with inhalational anaesthetics such as halothane -see Anaesthetics, general + Inotropes and Vasopressors , p.99. However, it is considered that it is much less likely than adrenaline (epinephrine) to have this effect, since it has primarily alpha-agonist activity. ... 

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