This also applies to some genetic variants which by themselves only minimally prolong the QT interval but can make people more susceptible to significant drug-induced QT prolongation. Mechanisms
The various forms of long QT syndrome, both congenital and acquired, produce abnormal heart rhythms (arrhythmias) by influencing the electrical signals used to coordinate individual heart cells. The common theme is a prolongation of the cardiac action potential – the characteristic pattern of voltage changes across the cell membrane that occur with each heart beat. Heart cells when relaxed normally have fewer positively charged ions on the inner side of their cell membrane than on the outer side, referred to as the membrane being polarised. When heart cells contract, positively charged ions such as sodium and calcium enter the cell, equalising or reversing this polarity, or depolarising the cell. After a contraction has taken place, the cell restores its polarity (or repolarises) by allowing positively charged ions such as potassium to leave the cell, restoring the membrane to its relaxed, polarised state. In long QT syndrome it takes longer for this repolarisation to occur, shown in individual cells as a longer action potential while being marked on the surface ECG as a long QT interval.The prolonged action potentials can lead to arrhythmias through several mechanisms. The arrhythmia characteristic of long QT syndrome, Torsades de Pointes, starts when an initial action potential triggers further abnormal action potentials in the form of afterdepolarisations.
Tiotixene, or thiothixene, sold under the brand name Navane among others, is a typical antipsychotic of the thioxanthene class which is related to chlorprothixene and is used in the treatment of psychoses like schizophrenia and bipolar mania. It was introduced in the United States in 1967 by Pfizer.Tiotixene is also related to thioproperazine and pipotiazine, members of the phenothiazine class. Pharmacology
Pharmacodynamics
Tiotixene acts primarily as a highly potent antagonist of the dopamine D2 and D3 receptors (subnanomolar affinity). It is also an antagonist of the histamine H1, α1-adrenergic, and serotonin 5-HT7 receptors (low nanomolar affinity), as well as of various other receptors to a much lesser extent (lower affinity). It does not have any anticholinergic activity. Antagonism of the D2 receptor is thought to be responsible for the antipsychotic effects of tiotixene. History
Tiotixene was introduced in 1967. Chemistry
Tiotixene is a member of the thioxanthene class of antipsychotics. Analogues include chlorprothixene, clopenthixol, flupentixol, and zuclopenthixol. == References ==