Effects of intravenous diazepam pretreatment on lactate-induced panic.

The psychological and physiological effects of acute low-potency benzodiazepine administration on lactate-induced panic were examined in 10 patients with panic disorder (PD). The patients, who had panicked during a standard sodium-lactate infusion, underwent a repeat infusion modified by pretreatment with intravenous diazepam (5 mg). Acute Panic Inventory (API) scores preceding the second lactate infusion, which were associated with diazepam pretreatment, were significantly reduced in compared with those measured before the first lactate infusion. However, the second visit "fear of doom" item of the API was significantly reduced relative to the same time point of the first visit 35 min before lactate infusion, when diazepam had not yet been administered. Thus, the reduction of prelactate anxiety preceding the second infusion appeared to reflect both pharmacological and nonpharmacological contributions. The diazepam pretreatment condition was associated with a significantly increased infusion duration and a significant attenuation of rate of API symptom increase in response to lactate. Despite significant attenuation of lactate infusion effects associated with the diazepam pretreatment condition, 7 of 10 patients experienced a second panic attack. This pilot study suggests that diazepam pretreatment is associated with a marked reduction of symptomatic response during a second lactate infusion, although the magnitude of attenuation observed was insufficient to block lactate-induced panic in a majority of lactate-vulnerable PD patients.

Noradrenergic function in panic disorder. Effects of intravenous clonidine pretreatment on lactate induced panic.

To assess the role of noradrenergic stimulation during lactate-induced panic, ten patients with panic disorder who panicked during a standard sodium-lactate infusion underwent a repeat infusion following intravenous clonidine pretreatment. Although clonidine significantly lowered prelactate systolic blood pressure, the drug did not significantly lower prelactate anxiety levels, as reflected by the Acute Panic Inventory (API). Clonidine blocked lactate-induced panic in four of ten subjects, a significant effect. Clonidine treatment also significantly attenuated lactate-panic symptoms, as reflected by time to panic and API comparison between trials. Nevertheless, over half the subjects still panicked in response to lactate despite clonidine. This preliminary study suggests that reduction of central noradrenergic activity by clonidine, at least at the dosage levels employed in the current study, only partially attenuates panic response to lactate. Noradrenergic theories of panic may not therefore fully account for lactate panicogenesis.

Do panic disorder patients indiscriminately endorse somatic complaints?

Ehlers et al. (1986b) and Margraf et al. (1986) suggested that panic disorder patients indiscriminately endorse somatic complaints and that their responses to lactate infusion are nonspecific. Their Symptom Questionnaire was composed of anxiety/panic/lactate infusion relevant symptoms, while the Somatic Control Scale was composed of "irrelevant" symptoms. In an attempt to address and in part replicate the above findings among panic disorder patients, we adopted the SCS of Margraf et al. (1986) for use with our Acute Panic Inventory, an instrument similar to their Symptom Questionnaire. Contrary to their reports, we did not find a tendency for panic patients to indiscriminately endorse somatic complaints. Only Acute Panic Inventory scores differed significantly across assessment points.

A comparison of sodium bicarbonate and sodium lactate infusion in the induction of panic attacks.

Infusion of sodium lactate has been shown by a number of investigators to induce panic in patients with panic disorder, but the pathophysiology underlying this phenomenon is unknown. One theory to explain lactate's anxiety-producing effects involves its ability to induce alkalosis because of metabolic conversion to bicarbonate. To test this hypothesis, we administered both sodium lactate and sodium bicarbonate infusions in counterbalanced order to patients with panic disorder. Thirteen of 22 subjects panicked in response to lactate and nine of 20 subjects panicked in response to bicarbonate. Although the rate of panic between the two infusion responses was not significantly different, several aspects of response to the two infusions indicated that lactate may be a more potent producer of anxiety than bicarbonate. An unexpected finding was that bicarbonate panickers had a reduction in arterial carbon dioxide pressure during the infusion, while bicarbonate nonpanickers had an increase in arterial carbon dioxide pressure during the infusion. Induction of hyperventilation and subsequent hypocapnia appears to be a common denominator between lactate- and bicarbonate-induced panic.

Measurement of lactate-induced panic and anxiety.

Acute Panic Inventory (API) scores were obtained from 26 normal controls and 89 patients with either panic disorder or agoraphobia with panic attacks before and during lactate infusions. Retrospective ratings of the patients' usual spontaneous attacks were much higher, by API, than ratings of moments of severe stress by the controls. Point of panic API scores, as well as increments of panic scores over prelactate scores, were higher for patients who experienced lactate panics than for both controls and patients who did not panic.

Effects of naloxone on patients with panic attacks.

To determine whether endogenous opiates are involved in panic anxiety, the authors challenged 12 patients with panic attacks with intravenous naloxone hydrochloride alone or combined with sodium lactate. Naloxone did not produce panic attacks or alter responses to lactate.

Effect of acute beta-adrenergic blockade on lactate-induced panic.

Many clinical and theoretic attempts have been made to link anxiety disorders and the beta-adrenergic nervous system. Six patients with panic disorder, who had panic attacks produced by sodium lactate infusions, were given repeated lactate infusions that were immediately preceded by intravenous administration of propranolol hydrochloride. In all cases, propranolol pretreatment infusion failed to prevent panic attacks, anxiety, tachycardia, and increased systolic BP during the lactate infusion.