) Corta-Fen Paste is used for temporary relief of minor muscle soreness and joint conditions. Fast and effective, with dramatic results within hours. Corta-Fen can help prepare your horse to perform at the highest level during big events. Corta-Fen Paste contains a formulation of high-strength Corta-Flx with a blend of all- natural plant flavonoids and botanical extracts. Corta-Fen contains natural, test-free ingredients. Give 30 ml 24 hours prior to event, repeat 6-12 hours prior to event.