When can a person become intolerant to a drug?

A person can become intolerant to a drug after prolonged use, when the body adapts to the medication and requires higher doses to achieve the same effect. This can occur due to metabolic changes, receptor desensitization, or other physiological adaptations. Additionally, some individuals may develop intolerances more quickly due to genetic factors or underlying health conditions. It's important to monitor any adverse reactions and consult a healthcare professional if drug intolerance is suspected.