Hyperhidrosis is characterized by excessive sweating due to the overstimulation of eccrine sweat glands by acetylcholine, a neurotransmitter involved in the process. This condition can be primary, manifesting early in life, or secondary, which is often a result of systemic or neurological diseases or as a side effect of certain medications.

The most frequent cause of secondary hyperhidrosis is medication. Various drugs can influence the body’s temperature regulation by acting on the hypothalamus, spinal thermoregulatory centers, sympathetic ganglia, or directly at the eccrine-neuroeffector junction. This often occurs due to the influence of medications that inhibit acetylcholinesterase, an enzyme responsible for breaking down acetylcholine, thus leading to increased sweating.

Drugs commonly associated with inducing hyperhidrosis include those used in psychiatric treatments such as selective serotonin reuptake inhibitors (SSRIs) like citalopram, tricyclic antidepressants like amitriptyline, and antipsychotics such as haloperidol and clozapine. Medications for dementia or Parkinson’s disease, such as acetylcholinesterase inhibitors like donepezil, also contribute to excessive sweating by stimulating sweat gland receptors.

Pain medications, including opioids like morphine and oxycodone and non-steroidal anti-inflammatory drugs (NSAIDs) such as celecoxib, can induce sweating. Furthermore, antimicrobials like cephalosporins and quinolone antibiotics, as well as antivirals, are also known to cause this condition. Drugs affecting endocrine functions, including systemic corticosteroids, thyroid medications, and diabetic treatments like insulin, may also lead to hyperhidrosis.

Non-prescription substances such as alcohol and caffeine can cause generalized hyperhidrosis upon withdrawal. In contrast to primary hyperhidrosis, which typically occurs symmetrically and reduces at night, drug-induced hyperhidrosis can be unilateral, asymmetrical, or generalized and may persist during sleep.

The Hyperhidrosis Disease Severity Scale is a tool comprising a four-point questionnaire designed to measure the extent to which the condition affects a patient’s everyday life. Patients select one of the following options to indicate their experience:

1.         My sweating is never noticeable and never interferes with my daily activities

2.         My sweating is tolerable but sometimes interferes with my daily activities

3.         My sweating is barely tolerable and frequently interferes with my daily activities

4.         My sweating is intolerable and always interferes with my daily activities.

If left untreated, hyperhidrosis may result in skin infections, including pitted keratolysis.

The impact of drug-induced hyperhidrosis extends beyond physical discomfort, often leading to social embarrassment, decreased self-confidence, and significant emotional stress. Diagnosis is typically clinical, focused on identifying a temporal relationship between the start of a medication and the onset of symptoms, excluding other potential causes of secondary hyperhidrosis.

For confirmation, physical examinations assess the pattern and location of sweating. The Minor starch-iodine test and gravimetric analysis can confirm localized sweating indicative of primary hyperhidrosis, but no lab tests confirm drug-induced hyperhidrosis directly.

Management strategies include discontinuing the offending medication, reducing its dosage, switching to an extended-release formulation, or substituting it with an alternative less likely to cause sweating. 

Treatments designed to reduce excessive sweating include the use of topical aluminum chloride in antiperspirants and topical anticholinergic agents such as glycopyrrolate or oxybutynin gel. Oral anticholinergic medications, including oxybutynin and benztropine, are also employed but can have side effects like dry mouth, constipation, and blurred vision. For localized hyperhidrosis, botulinum toxin injections are an approved option, particularly for underarm sweating. Another method, iontophoresis, involves passing an electric current through water-soaked skin, potentially with the addition of an anticholinergic medication. 

Typically, drug-induced hyperhidrosis will resolve once the triggering medication is discontinued.

Addressing drug-induced hyperhidrosis effectively requires a thorough understanding of the medications involved and a comprehensive approach to treatment, emphasizing both medication management and symptom control. This ensures not only the alleviation of physical symptoms but also helps mitigate the psychological impacts associated with this challenging condition.