Why the nasal spray stopped working
Intranasal desmopressin is absorbed through the nasal mucosa. When the nose is congested or full of discharge, as with a head cold, the spray may not reach the absorbing surface, may run out of the nose, or may be swallowed. Less drug is absorbed, so his kidneys again receive too little antidiuretic effect, and polyuria and thirst return. A blocked nose reduces absorption of desmopressin nasal spray, causing under-dosing symptoms even when no doses are missed.
What the nurse advises
The nurse advises him to contact his provider about using an oral or other route until the congestion clears. Meanwhile, he should drink according to thirst so that he does not become dehydrated, monitor his weight and urine output, and seek care if he develops dizziness, confusion, or signs of significant dehydration. Once the cold resolves, absorption usually returns to normal, and he can resume the nasal spray if the provider agrees.
| Explanation | Likely? | Reason |
|---|
| Cold reduced his own vasopressin | No | His production is already deficient |
| Extra fluids diluting urine | No | Would not cause heavy urination if the drug were absorbed |
| Nasal congestion reducing absorption | Yes | Blocked nose prevents mucosal absorption |
| Kidneys stopped responding | No | Resistance does not develop suddenly with a cold |
Why the other explanations are wrong
His own vasopressin production is already deficient, which is why he needs the drug, so a cold reducing it further would not explain a new change. Drinking extra fluids for a cold could increase urine slightly, but if the drug were being absorbed normally, his kidneys would still concentrate urine and he would not develop heavy urination with marked thirst. Sudden kidney resistance to vasopressin does not develop with a cold. Watch out! When a drug given by a specific route stops working, think first about whether the route is still delivering the drug.
Exam takeaway
Teaching for nasal desmopressin includes correct spray technique, the effect of colds, allergies, or nasal surgery on absorption, and when to call for a route change. Key point! Nasal congestion reduces absorption of desmopressin spray; the client should contact the provider about an alternative route.