Effect of some related drugs on the fluorometric determination of 3 μg mL⁻¹ KPN, 1.5 μg mL⁻¹ PAR and 5 μg mL⁻¹ CLX.

Drug	Reason for interference	Drug tolerance limit (μg mL−1)
Phenylephrine hydrochloride	- It is used to relieve nasal discomfort caused by colds, allergies, and hay fever	173 for KPN 234 for PAR
	-Commonly co-administered with PAR or KPN
Tizanidine	- Muscle relaxant	112 for KPN 164 for PAR
	- Commonly co-administered with PAR or KPN
Venlafaxine	- An antidepressant medication	89 for KPN 120 for PAR 125 for CLX
	- Could be administered with any of the studied drugs
Diacerein	- Used to treat joint diseases such as osteoarthritis	32 for KPN 40 for PAR 48 for CLX
	- Could be administered with any of the studied drugs
Diclofenac sodium	Analgesic which is commonly prescribed with CLX	50 for CLX
Mefenamic acid	Non-steroidal anti-inflammatory drug which is commonly prescribed with CLX	7 for CLX
Aceclofenac	Non-steroidal anti-inflammatory drug which is commonly prescribed with CLX	140 for CLX
Ibuprofen	Analgesic which is commonly prescribed with CLX	240 for CLX