Antipsychotic agents causing

The answer is d, (Katzung, p 482.) Although many antipsychotic agents can cause orthostatic hypotension, chlorpromazine is the most likely choice of the agents above for causing this adverse effect. 

These antihistamines infreguently cause typical phenothiazine adverse effects. See the Antipsychotic Agents monograph for a complete discussion. 

The Rauwolfla alkaloid reserpine was originally used as a neuroleptic/antipsychotic agent. It was then discovered to be an effective antihypertensive agent. Reserpine causes depletion of the noradrenaline stores in peripheral postganglionic sympathetic neurons. In addition it causes depletion of noradrenalin in central nervous structures involved in the regulation of blood pressure. 

Most antipsychotics and especially the piperazines and the butyrophenones can cause extrapyra-midal symptoms. Blockade of dopamine receptors mainly in the corpus striatum is held responsible for these extrapyramidal effects. They may become manifest as a variety of clinical symptoms and it should be noted that within 24 8 hours after the beginning of treatment acute dystonic reactions like torticollis, facial grimacing and opisthotonos may occur. Parkinsonism-like symptoms such as bradyki-nesia, rigidity and tremor occur after weeks or months of therapy and are more common in the elderly. Motor restlessness, i.e. akathisia, also mostly occurs not before weeks or months after starting therapy. The tendency of an antipsychotic agent to produce extrapyramidal symptoms appears to be inversely related to its ability to block cholinergic receptors. 

EPS include acute dystonic reactions, parkinsonian syndrome, akathisia, tardive dyskinesia, and neuroleptic mahgnant syndrome. Although high-potency conventional antipsychotics are more hkely than low-potency conventional antipsychotics to cause EPS, all first-generation antipsychotic drugs are equally hkely to cause tardive dyskinesia. The atypical antipsychotics cause suhstantially fewer EPS, which is one reason that they are recommended as first-line agents. 

Because the tardive syndromes that develop in adults are often irreversible and have no satisfactory treatment, care must be taken to reduce the likelihood of their occurrence. Antipsychotic medication should be prescribed only when necessary and should be withheld periodically to assess the need for continued treatment and to unmask incipient dyskinesia. Thioridazine, a phenothiazine with a piperidine side chain, is an effective antipsychotic agent that seems less likely than most to cause extrapyramidal reactions, perhaps because it has little effect on dopamine receptors in the striatal system. Finally, antimuscarinic drugs should not be prescribed routinely in patients receiving neuroleptics, because the combination may increase the likelihood of dyskinesia. 

In contrast to other antipsychotic agents, clozapine causes agranulocytosis in a small but significant number of patients—approximately 1-2% of those treated. This serious, potentially fatal effect can develop rapidly, usually between the 6th and 18th weeks of therapy. It is not known whether it represents an immune reaction, but it appears to be reversible upon discontinuance of the drug. Because of the risk of agranulocytosis, patients receiving clozapine must have weekly blood counts for the first 6 months of treatment and every 3 weeks thereafter. 

Antipsychotic drugs include the older phenothiazines and butyrophenones, as well as newer atypical drugs. All of these can cause CNS depression, seizures, and hypotension. Some can cause QT prolongation. The potent dopamine D2 blockers are also associated with parkinsonian-like movement disorders (dystonic reactions) and in rare cases with the neuroleptic malignant syndrome, characterized by "lead-pipe" rigidity, hyperthermia, and autonomic instability (see Chapter 29 Antipsychotic Agents Lithium). 

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