A patient taking disulfiram to support abstinence from alcohol decides to yield to his temptation and starts drinking but only a day after stopping disulfiram.
Which one of the following is correct in this scenario?
D. Alcohol (ethanol) is metabolized via an oxidation reaction catalysed by alcohol dehydrogenase. This results in formation of acetaldehyde, which is further broken down to acetyl-coenzyme A by aldehyde dehydrogenase. Disulfiram is a non-competitive, irreversible aldehyde dehydrogenase inhibitor. So when alcohol is taken together with disulfiram this leads to accumulation of acetaldehyde. A high level of acetaldehyde is associated with nausea, throbbing headache, vomiting, hypertension, flushing, sweating, thirst, dyspnoea, tachycardia, chest pain, vertigo, and blurred vision. The accumulation of acetaldehyde occurs almost immediately after the ingestion of alcohol in those who take disulfiram; the reaction can last from 30 minutes to 2 hours. The initiation of disulfiram should not take place unless the patient has abstained from alcohol for at least 12 hours. Its half-life is estimated to be 60 to 120 hours. The effect of disulfiram treatment can last as long as 1 or 2 weeks after the last dose of disulfiram. Most fatal reactions occur in persons who are taking more than 500 mg a day of disulfiram and who consume more than 90 g of alcohol.
References:
Smoking can reduce extrapyramidal side-effects caused by antipsychotics through:
A. Cigarette smoking occurs at a very high rate in patients with schizophrenia. Many reasons have been proposed as to why such high rates of smoking are seen in schizophrenia patients. One suggestion is that patients smoke as a form of self-medication with nicotine, which may help to regulate a dysfunctional mesolimbic dopamine system. Nicotine can increase dopamine release in the prefrontal cortex and reduce negative symptoms to some extent. Nicotine could enhance cognitive performance for certain tasks. Antipsychotic medications could block the dopamine reward pathway, necessitating an increase in nicotine concentrations needed to produce reward effects from smoking. Smoking may decrease the plasma levels of typical antipsychotic drugs via induction of the CYP450 enzymes system, providing some relief from extrapyramidal side-effects, but most patients who smoke start smoking even before onset of the illness.
Acamprosate is used in the management of alcohol dependence. Which of the following is correct?
B. Acamprosate is a structural analogue of GABA and taurine. Its mechanism of action is thought to be antagonism of glutamatergic N-methyl-D-aspartate (NMDA) receptors. It should only be started after the individual has been successfully weaned off alcohol; this is not because of alcohol–acamprosate interaction but the efficacy of acamprosate is demonstrated only in individuals who have been successfully detoxified from alcohol. The concomitant intake of alcohol and acamprosate does not affect the pharmacokinetics of either alcohol or acamprosate, but if the patient relapses more than once while on acamprosate the treatment must be reconsidered. Administration of disulfiram does not affect the pharmacokinetics of acamprosate; though this is practiced at certain centres, no strong evidence exists to support the combination. Bupropion, used to aid abstinence from smoking, is started 2 weeks before a target date is set to quit smoking.
Reference:
The most common reason for using dantrolene sodium in psychiatric patients is:
C. Dantrolene sodium is used to treat rigidity and hyperthermia in patients with neuroleptic malignant syndrome (NMS). Dantrolene binds to a calcium channel called ryanodine receptor in skeletal muscle, leading to a fall in intracellular calcium concentration and reduced contraction. It is usually administered via the intravenous route; it reduces muscle spasm in most patients with neuroleptic malignant syndrome. Dantrolene is not a stand-alone treatment for NMS; it must be accompanied by resuscitation, fluid replacement, and cardiac and respiratory support. Rigidity is relieved usually within minutes to hours of administration. Dantrolene can also be used in other cases of life-threatening muscle rigidity, for example catatonia and serotonin syndrome.
Which of the following is correctly paired?
E. Haloperidol is chemically a butyrophenone. Fluphenazine, perphenazine, and trifluperazine are piperazine phenothiazines. Chlorpromazine is an aliphatic phenothiazine while thioridazine is a piperidine phenothiazine. Thiothixene is a thioxanthene antipsychotic; pimozide is a diphenyl butyl piperidine. Loxapine is a dibenzoxapine. Many of these typical antipsychotics are rarely used in current practice.
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