We are truly heartsick to hear about the struggles of your brother. Depression is a real burden and it is a spiritual battle. God wants us to cast all our anxieties on Him because He cares for us.
We are called to bear one another's burdens, and we will lift your brother up in prayer, asking God to comfort and heal him.
Firstly, we must acknowledge that the situation is not just a mental and emotional battle. The Apostle Paul tells us in Ephesians 6:12, "For we are not wrestling against flesh and blood, but against the principalities, against the powers, against the world's rulers of the darkness of this age, and against the spiritual forces of wickedness in the heavenly places. We will begin the prayer by warring against these principalities, powers, and the spiritual forces of wickedness.
We must stand against the devil's schemes. Your brother has an addiction and the enemy is using this to slowly kill him and destroy his life. Our Lord Jesus Christ becomes the advocate for each person who comes to Him.
Fleeing and avoiding temptation is critical. God knows and understands our temptations, and He provides a way out. 1 Corinthians 10:13 promises, "No temptation has taken you except what is common to man. God is faithful, who will not allow you to be tempted above what you are able, but will with the temptation also make the way of escape, that you may be able to endure it."
WEB, "Hope in God; for I will still give him praise, my Salvation and my God." Psalm 42:11. Repeat his name over and over and over and meditate on the Word of God. The Bible assures us that God will never leave us nor forsake us.
Your brother is not alone. God is with him, and we are praying for him. Let us pray together:
Dear Heavenly Father,
We come before You today, lifting up the brother of the one who submitted this request. Lord, You know the depths of his depression and the power of the drug addiction has over his life. We stand here today and say NO to the devil's schemes. We know that he is not wrestling against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.
Father, we call upon the name of Jesus and ask that You would remind this brother that You are always with him. Jesus Christ is our advocate during our time of need. We pray that You will surround him with your love and comfort and give him a sense of hope.
Lord, we ask that You would break the chains of addiction in his life and give him the strength to resist temptation. We pray that you would provide him with a way out, that he may be able to endure it. We ask that You would heal his mind and body, and give him the courage to seek help and cooperate with those who love him.
We come to you in the only way that we can by the name of Jesus Christ our Lord and Savior.
In Jesus Name, Amen.
Prayer Focus: God, Thank You. Thank You for loving me. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
