The only additional deductions you may be eligible to claim for your parent would be the Child and Dependent Care Credit or possibly an itemized deduction for medical expenses that you paid.
The Child and Dependent Care Credit would require you to pay someone else to care for your parent while you were working. This is typically claimed by taxpayers who have a child in daycare while they work, but it is available in the case where the dependent is not a child, but another dependent.
To get any tax benefits for claiming medical expenses that you paid on behalf of your parent, you would need to be paying more than 7.5% of your Adjusted Gross Income in medical expenses and be claiming itemized deductions on Schedule A.
Neither of these situations are very common, so the $500 Other Dependent Credit is most likely the maximum that you would receive. Rent and over the counter medications are not deductible.
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