Tachycardia drug-induced

Finally, the ICH E14 guideline does not address the possible consequences of QT/ QTc shortening, which may be associated with significant arrhythmias [5,167]. Digitalis intoxication is a known example of drug-induced short QT syndrome associated with polymorphic ventricular tachycardia [ 168]. It should be acknowledged that this is an area of active research and no guidelines can be put forward at the moment. 

Adverse effects include local stinging or burning, sneezing, dryness of mouth and throat. Prolonged use may cause rebound congestion and drug induced rhinitis, headache, tachycardia may occur. 

Cyclizine has antimuscarinic properties and is a potent anti-emetic, effective for the control of postoperative and drug-induced nausea and vomiting. It has been used to prevent motion sickness, although diphenhydramine and promethazine are more effective. It is available in oral and parenteral formulations. In contrast to many other first-generation antihistamines sedation is not marked. It is available in tablet form as the hydrochloride and in injectable form as the lactate. Because of its anticholinergic action, blurred vision and dry mouth are associated with clinical doses. When given by rapid intravenous injection tachycardia may be a problem. Meclozine is a related drug which, like cyclizine, is used primarily for motion sickness. 

Phenylephrine is indicated in the treatment of vascular failure in shock, shock-like states, drug-induced hypotension, or hypersensitivity to overcome paroxysmal supraventricular tachycardia to prolong spinal anesthesia as a vasoconstrictor in regional analgesia and to maintain an adequate level of BP during spinal and inhalation anesthesia. Phenylephrine is a powerful postsynaptic alpha-receptor stimulant with little effect on the beta receptors of the heart (see also Figure 39). 

Antiarrhythmic drugs that block potassium channels, such as sotalol and quinidine, can cause the polymorphic ventricular tachycardia known as torsades de pointes (see Chapter 34). The abnormal repolarization that leads to polymorphic ventricular tachycardia is potentiated by hypokalemia, and diuretics that produce potassium loss increase the risk of this drug-induced arrhythmia. 

A. Hydralazine and Minoxidil These older vasodilators have more effect on arterioles than on veins. They are orally active and suitable for chronic therapy. Hydralazine apparently acts through the release of nitric oxide. However, it is rarely used at high dosage because of its toxicity therefore, its efficacy is limited, fts toxicities include compensatory responses (tachycardia, salt and water retention Table 11-2) and drug-induced lupus erythematosus, which is reversible upon stopping the drug. However, this effect is uncommon at dosages below 200 mg/d. 

The amide local anaesthetic lidocaine may also be used as an antianhythmic for ventricular tachycardia and exra-systoles after injection into the blood circulation. Drugs with high lipid solubility such as bupivacaine cannot be used for these purposes because their prolonged binding to the channel may induce dysrhythmias or asystolic heart failure [3]. Systemically applied lidocaine has also been used successfully in some cases of neuropathic pain syndromes [4]. Here, electrical activity in the peripheral nervous system is reduced by used-dependent but incomplete sodium channel blockade. 

Malignant hyperthermia (MH) is an autosomal-dominant pharmacogenetic disorder that is triggered by exposure to inhalation of general anesthetics, such as halothane. In susceptible individuals, these drugs can induce tachycardia, a greatly increased body metabolism, muscle contracture and an elevated body temperature (above 40°C) with a rapid rate of increase. Many cases of MH are linked to a gene for type 1 ryanodine receptor (RyRl). 

Bepridil has Class I antiarrhythmic properties and, like other such drugs, can induce new arrhythmias, including ventricular tachycardia/ventricular fibrillation (VTA/F). In addition, because of its ability to prolong the QT interval, bepridil can cause torsades de pointes type VT. Because of these properties, reserve bepridil for patients in whom other antianginal agents do not offer a satisfactory effect (see Warnings). P.285... 

Carvedilol (1) reduces cardiac output, (2) reduces exercise- or isoproterenol-induced tachycardia, and (3) reduces reflex orthostatic tachycardia. Significant -blocking effect is usually seen within 1 hour of drug administration. 

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