Pharmacology
Respiratory
Regarding antimuscarinic bronchodilators, which of the following statements is CORRECT:
Answer:
There are no important drug interactions with inhaled muscarinic antagonists. Inhaled antimuscarinics are generally well tolerated as they are poorly absorbed systemically. Ipratropium bromide has its maximal effect 30 – 60 minutes after use and its duration of action is 3 to 6 hours. Ipratropium bromide can provide short-term relief in chronic asthma, but short-acting beta-2 agonists act more quickly and are preferred. Ipratropium bromide by nebulisation can be added to other standard treatment in life-threatening asthma or if acute asthma fails to improve with standard therapy.Inhaled Antimuscarinics
Pharmacology / Respiratory
Last Updated: 28th March 2019
Ipratropium bromide, a short-acting antimuscarinic bronchodilator, causes bronchodilation by blocking the cholinergic nerves in the airways.
Indications
Ipratropium bromide can provide short-term relief in chronic asthma, but short-acting beta-2 agonists act more quickly and are preferred. Ipratropium bromide by nebulisation can be added to other standard treatment in life-threatening asthma or if acute asthma fails to improve with standard therapy.
The aerosol inhalation of ipratropium bromide may be used for short-term relief in mild COPD in patients who are not using a long-acting antimuscarinic drug. Its maximal effect occurs 30 – 60 minutes after use; its duration of action is 3 to 6 hours and bronchodilation can usually be maintained with treatment 3 times a day.
Cautions
Ipratropium bromide should be used with caution in:
- Men with prostatic hyperplasia and bladder-outflow obstruction (worsened urinary retention has been reported in elderly men)
- People with chronic kidney disease (CKD) stages 3 and above (because of the risk of drug toxicity)
- People with angle-closure glaucoma (nebulised mist of antimuscarinic drugs can precipitate or worsen acute angle-closure glaucoma)
Interactions
There are no important drug interactions with inhaled muscarinic antagonists.
Side Effects
Inhaled antimuscarinics are generally well tolerated as they are poorly absorbed systemically.
Their adverse effects include:
- Dry mouth and abnormal taste in the mouth
- Nasal congestion and dryness of nasal mucosa
- Acute angle-closure glaucoma (reported in people on nebulised ipratropium)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
