can I claim methadone treatment for addiction

Yes, your methadone treatment would be considered a medical expense, so yes, both the cost of the drugs and the mileage would be deductible. In order to claim the methadone expenses you paid you would have to itemize your return instead of taking the standard deduction. 

Itemized expenses include mortgage interest, gambling losses up to winnings,  charitable contributions, state and local taxes up to $10,000, medical expenses in excess of 7.5% of your AGI and casualty and losses in excess of 10% of you AGI with the first $100 not counting towards the loss.  Your health insurance and all medical expenses are only deductible for the amount that is over 7.5% of your AGI.  This means if your AGI is $50,000, then the amount that is over $3,750 is deductible.  

Then your total itemized expenses would need to be greater than your standard deduction below in order to benefit from your expenses. 

The 2024 Standard Deductions are as follows:

• Married Filing Joint (MFJ)              $29,200
• Married Filing Separate (MFS)      $14,600
• Head of Household (HOH)             $21,900 
• Single                                                 $14,600                                

Blind or over 65 and MFJ or MFS add $1,550

Single or HOH if blind or over 65 add $1,950

Standard versus Itemized Deduction