Poor compliance of drugs by the patients.

Causes for poor compliance include:[1]
• Forgetfulness
• Prescription not collected or not dispensed
• Purpose of treatment not clear
• Perceived lack of effect
• Real or perceived side-effects
• Instructions for administering not clear
• Physical difficulty in complying (e.g. with opening medicine containers, handling small tablets or swallowing difficulties, travel to place of treatment)
• Unattractive formulation (e.g. unpleasant taste)
• Complicated regimen
• Cost of drugs