ATS Pulmonary Function Laboratory Manual

ATS Pulmonary Function Laboratory Management & Procedure Manual | 3rd Edition

2.

Diluent 2.1.

Methacholine should be diluted using a sterile sodium chloride (NaCl) solution (0.9%) with or without 0.4% phenol. There is no evidence that adding a preservative such as phenol to sterile NaCl diluent is necessary (13), nor is there evidence that use of phenol adversely affects the methacholine challenge test. The potential benefit of adding phenol is reducing the potential for bacterial contamination (10). 2.2. The use of a buffer had previously been recommended (14), but may render the solution too alka- line, which may lead to methacholine decomposition (15, 16). 3. Methacholine Solution Preparation 3.1. Methacholine powder is very hygroscopic, meaning it readily absorbs moisture. If bulk quantities of methacholine are kept, the powder should be stored in a dry container (desiccator) in a refrigerator or freezer (17). 3.2. Methacholine solutions should be mixed by a pharmacist or other qualified, well-trained individual using sterile technique and following the manufacturer’s instructions (10). 3.3. The recommended approach is to use the sealed 100 mg Provocholine vials. The dilution schemes for two dosing schedules using the 100 mg Provocholine vials are shown in Tables 12.3 and 12.4 (10). An example of a dosing protocol is shown in Appendix 12.5.

Table 12.3

Dilution Schedule for Doubling Doses

Label Strength Take

Add Diluent

Obtain Dilution

100 mg

100 mg

6.25 ml

16 mg/ml 8 mg/ml 4 mg/ml 2 mg/ml 1 mg/ml 0.5 mg/ml 0.25 mg/ml 0.125 mg/ml 0.0625 mg/ml 0.031 mg/ml 0.015625 mg/ml

3 ml of 16 mg/ml 3 ml of 8 mg/ml 3 ml of 4 mg/ml 3 ml of 2 mg/ml 3 ml of 1 mg/ml 3 ml of 0.5 mg/ml 3 ml of 0.25 mg/ml 3 ml of 0.125 mg/ml 3 ml of 0.0625 mg/ml 3 ml of 0.031 mg/ml

3 ml 3 ml 3 ml 3 ml 3 ml 3 ml 3 ml 3 ml 3 ml 3 ml

124