Eutectic formulations of cyclobenzaprine hydrochloride and amitriptyline hydrochloride

1. A pharmaceutical composition of comprising a eutectic of Amitriptyline HCl and mannitol, wherein the pharmaceutical composition comprises amounts of Amitriptyline HCl and mannitol selected from: 40%±2% Amitriptyline HCl and 60%±2% mannitol, 45%±2% Amitriptyline HCl and 55%±2% mannitol, 50%±2% Amitriptyline HCl and 50%±2% mannitol, 55%±2% Amitriptyline HCl and 45%±2% mannitol, 60%±2% Amitriptyline HCl and 40%±2% mannitol, 65%±2% Amitriptyline HCl and 35%±2% mannitol, 70%±2% Amitriptyline HCl and 30%±2% mannitol, 80%±2% Amitriptyline HCl and 20%±2% mannitol, 85%±2% Amitriptyline HCl and 15%±2% mannitol, and 90%±2% Amitriptyline HCl and 10%±2% mannitol by weight.

2. The pharmaceutical composition of claim 1 , wherein the pharmaceutical composition comprises 60%-90% Amitriptyline HCl and 40%-10% mannitol by weight.

3. The pharmaceutical composition of claim 1 , comprising 50%±2% Amitriptyline HCl and 50%±2% mannitol by weight.

4. The pharmaceutical composition of claim 1 , wherein the Amitriptyline HCl is micronized Amitriptyline HCl.

5. The pharmaceutical composition of claim 1 , further comprising a basifying agent.

6. The pharmaceutical composition of claim 5 , wherein the basifying agent is K 2 HPO 4 , Na 2 HPO 4 or anhydrous trisodium citrate.

7. The pharmaceutical composition of claim 1 , wherein the mannitol in the eutectic is β mannitol.

8. The pharmaceutical composition of claim 1 , wherein the mannitol in the eutectic is δ mannitol.

9. The pharmaceutical composition of claim 7 or 8 , wherein the Amitriptyline HCl is micronized Amitriptyline HCl.

10. The pharmaceutical composition of claim 7 or 8 , further comprising a basifying agent.

11. The pharmaceutical composition of claim 10 , wherein the basifying agent is K 2 HPO 4 , Na 2 HPO 4 or anhydrous trisodium citrate.