Pilocarpine iontophoresis

Diagnosis of CF is based on two separate elevated sweat chloride concentrations of greater than or equal to 60 mEq/L (or mmol/L) obtained through pilocarpine iontophoresis (referred to as the sweat test ). Genetic testing (CFTR mutation analysis) may be performed to confirm the diagnosis, screen in utero, or detect carrier status. More than 70% of diagnoses are made by 12 months of age and almost all are made by age 12. 

The sweat test occurs in three phases sweat stimulation by pilocarpine iontophoresis collection of the sweat onto gauze, filter paper, coil, patch, or capillary tube and qualitative or quantitative analysis of sweat chloride, sodium, conductivity, or osmolality. A survey of 753 laboratories (Table 27-3) performing sweat testing revealed that 47% analyze chloride, 46% analyze conductivity, and less than 7% analyze sodium or osmolality. ... 

LeGrys VA, Retsch-Bogart G. Urticaria associated with the pilocarpine iontophoresis sweat test. Pediatr Pulmol 1977 24 296-7. 

Table 6.9 Steepest Ascent Optimization of Pilocarpine Iontophoresis [adapted from reference (8) by permission]...

Gibson, L.E., and R.E. Cooke. 1959. A test for concentration of electrolytes in sweat in cystic fibrosis of the pancreas utilizing pilocarpine by iontophoresis. Pediatrics Evanston) 23 545. 

The ease of application, the minimization of systemic side effects, and the increased drug penetration directly into the target region resulted in extensive clinical use of iontophoresis mainly in the transdermal field. This technique has been utilized for administration of local anesthetics [2-5], sweat chloride testing in cystic fibrosis patients by transcutaneous delivery of pilocarpine [6,7], administration of vidarabine to patients with herpes orolabialis [8], fluoride administration to patients with hypersensitive dentin [9,10], and gentamicin delivery for the management of burned ears [11],... 

One of the earliest FDA-approved products that utilized iontophoresis was the iontophoretic delivery of pilocaripne as a method for diagnosing cystic fibrosis [36], The sweat of individuals with cystic fibrosis contains large amounts of both sodium and chloride ions. The pilocarpine that is delivered into the skin promotes increased sweating, which can be easily collected and analyzed. 

Burns to the patient s skin after iontophoresis are extremely rare but can occur at either electrode. If the burn occurs at the site of pilocarpine stimulation, sweat should not be col-... 

Considerable progress has been made on several of these fundamental aspects of sweat analysis. For example, satisfactory stimulation of sweating is achieved with 500 mmol dm" pilocarpine nitrate in the iontophoresis stage using 1 mA current for 3 min, while a new pad to absorb acid and alkaline skin irritants is so satisfactory that a baby asleep at the start of a test will usually remain asleep throughout [265]. 

Iontophoresis of pilocarpine is the classical method for obtaining sweat for the cystic fibrosis test (Gibson and Cooke, 1959). The penetration of pilocarpine in the skin enhances sweat production. The test is usually performed on children with both electrodes placed on the underarm (for safety reasons, the current should not pass the thorax). A 0.5% solution of pilocarpine is placed under the positive electrode, and the DC current is slowly increased to a maximum of about 1.5 mA. The iontophoresis time is about 5 min. 

In order to collect the sweat for sodium or chloride measurement, a drug such as pilocarpine is introduced into the skin by iontophoresis (qv) in order to stimulate sweat production. The sweat is absorbed onto filter paper which has been placed on the skin. It is then eluted off the filter paper by placing the discs in distilled water. This is analysed for sodium or chloride content. 

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