A 2015 article discusses medications that can affect thermoregulation and predispose patients to a higher risk of dehydration and other heat-related illness. Antidepressants are among the known medications that can alter the body’s thermoregulatory response, which typically becomes apparent in warmer weather. The risk is especially of concern in older populations who are more susceptible to dehydration and heat stroke. Tricyclic antidepressants (TCAs) have strong anticholinergic effects, which can alter central thermoregulation. Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin and norepinephrine reuptake inhibitors (SNRIs) have also been implicated. Anticholinergic activity usually reduces sweating with TCAs, while SSRIs/SNRIs can cause excessive sweating. Antidepressants may also cause sedation and cognitive impairment, which reduce alertness and perception of hot weather. SSRIs and venlafaxine can also cause hyponatremia, potentially leading to impairment of fluid balance, dehydration, and heat stroke. [1]

To reduce the risk of dehydration and heat-related illness, the lowest effective dose for the shortest possible time should be prescribed. Patients on antidepressants should be counseled thoroughly regarding the risk of heat-related illness along with the early signs and symptoms of dehydration. Some suggest delaying medication until the hot weather has passed. Older adults should also receive guidance on how to stay well during hot weather, such as drinking small amounts of fluids, even when not thirsty; eating cold foods with high fluid content; remaining in a cool location indoors while wearing lightweight, loose clothing; and maintaining frequent contacts with friends, family, and providers. [1]

A 1996 article briefly discusses drug-induced heat intolerance in relation to a patient who developed heat stroke from a combination of fluoxetine and lithium. Fluoxetine inhibits the reuptake of serotonin and increased serotonin in the anterior hypothalamus, which has been linked to the stimulation of cholinergic heat-production pathways. Enhanced serotonin activity also inhibits dopaminergic heat-loss pathways in the hypothalamus. Lithium was used to enhance the serotonergic effects of fluoxetine, but may also have an independent effect on the development of heat stroke by inhibiting dopamine release which can inhibit heat-loss pathways, and enhance cholinergic heat-production pathways by inhibiting noradrenaline. The authors believe the synergistic effect was what led to heat intolerance and heat stroke in their patient case. [2]

All available antidepressants have been reported by their manufacturers to have a risk of causing effects that can contribute to heat intolerance. While manufacturers have explicitly warned that amoxapine or clompramine can cause a very high fever or neuroleptic malignant syndrome, heat intolerance-associated effects can also be caused by serotonin syndrome, which is a risk featuring a labeled warning with nearly all currently available antidepressants. Many antidepressants have also been reported to have anticholinergic-related effects (ex: duloxetine, amitriptyline, clomipramine, desipramine, imipramine), which may also contribute to heat intolerance. [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51], [52], [53], [54], [55], [56], [57], [58], [59]

A search of the published medical literature revealed 1 study investigating the researchable question:

Can you summarize any data regarding antidepressants resulting in heat intolerance? What are possible ways to reduce the risk of heat intolerance?

D - Case reports or unreliable data  Read more→