Buspirone overdose

No fatal outcomes of buspirone overdose have been reported. However, overdose of buspirone with other drugs may result in more serious outcomes. 

Azapirones. Though several azapirones have been developed and tested in the laboratory setting, only one, bnspirone (Bnspar), is currently on the market. Buspirone is the first nonsedating, nonbenzodiazepine anxiolytic, other than the antidepressants described earlier. It has no dependence or addictive liability and is not lethal in overdose. Buspirone is also devoid of many of the problems of the benzodiazepines such as sedation, motor impairment, addiction, physical dependence, or withdrawal. Yet, doubts remain in the minds of many practitioners regarding the effectiveness of buspirone. This will be discussed in more detail later in this chapter. 

Buspirone is well-tolerated, with the main side-effects being dizziness, anxiety, nausea and headache. It is tolerated by the elderly (Bohm et al. 1990). It does not cause sexual dysfunction and does not appear to be associated with a discontinuation syndrome. Overdose causes drowsiness but there are no reports of serious toxic effects. A potential for interaction with drugs that inhibit the CYP450 3A4 isoenzyme is not a significant problem in cHnical practice. GAD is usually a chronic condition and buspirone is suitable for long-term treatment. Patients should be advised to expect a slow onset of benefits and be reviewed regularly in the early stages of treatment. 

More recently, non-BZD anxiolytics, such as buspirone, and nonbarbiturate, non-BZD hypnotics, such as zolpidem and zaleplon, have been developed. The more recent anxiolytics and hypnotics offer equal efficacy, fewer serious adverse effects, and less risk of a fatal consequence due to accidental or intentional overdose. Unfortunately, these compounds have not entirely eliminated the hazards of tolerance, dependency, and withdrawal syndromes, although they do have a lower abuse potential than their predecessors. 

Non-reversible lithium neurotoxicity continues to be reported (165,166), including a case of lithium overdose (serum lithium concentration 3.9 mmol/1) with persistent severe ataxia for 9 months that improved markedly when inadvertently treated with high-dose buspirone (120-160 mg/day) (167). 

Elevated blood pressure has been reported in four patients taking buspirone and either phenelzine or tranylcypromine. Buspirone may have contributed to a case of the serotonin syndrome in a patient who overdosed on moclobemide and clomipramine. 

A severe case of the serotonin syndrome (including hyperthermia and muscle rigidity requiring mechanical ventilation) has been reported in a patient who took an overdose of moclobemide, clomipramine and buspirone , (p.l 149). Concurrent use of more than one serotonergic drug is thought to be a risk factor for the development of the serotonin syndrome , (p.9). 

A small study in healthy subjects found no problems when moclobemide was given 24 hours after clomipramine. However, the serotonin syndrome occurred in 3 patients when clomipramine was replaced by mo-clobemide without a washout period or with only a 24-hour washout period, " and in another patient when moclobemide was replaced by clomipramine after only 12 hours. A fatal case of the serotonin syndrome occurred in a patient taking clomipramine and amitriptyline, with symptoms manifesting within 30 minutes of a 300-mg dose of moclobemide. Two other patients developed fatal serotonin syndrome after taking moderate overdoses of moclobemide and clomipramine. The serotonin syndrome has been reported in at least 8 other cases of moclobemide and clomipramine overdose, one of which also involved tramadol (see also MAOIs + Opioids Tramadol, p.ll41), another fluoxetine (see also MAOIs or RIMAs + SSRIs, p.l 142), and yet another buspirone (see also MAOIs or RIMAs + Buspirone, p.l 133). Conversely, a case of an overdose of moclobemide and clomipramine resulted in no adverse effects except sinus tachycardia. ... 

---