Paracetamol metoclopramide interactions

Concomitant administration of paracetamol with other hepatotoxic drugs or drugs acting on liver microsomal enzymes enhances paracetamol toxicity. Other drugs that interact with paracetamol are metoclopramide, probenecid, and cholestyramine.81... 

Intravenous metoclopramide 10 mg increased the peak plasma levels of a single 1.5-g dose of paracetamol by 64% in 5 healthy subjects (slow absorbers of paracetamol), and increased its rate of absorption (peak levels reached in 48 minutes instead of 120 minutes), but the total amount absorbed remained virtually unaltered. Oral metoclopramide also increases the rate of paracetamol absorption, probably because the rate of gastric emptying is increased. Similarly, the speed of absorption of paracetamol may also be increased by domperidone. This interaction is exploited in Paramax (a proprietary oral preparation containing both paracetamol and metoclopramide) to increase the effectiveness and onset of analgesia for the treatment of migraine. This is obviously an advantageous interaction in this situation. 

Seaber EJ, Ridout G, Layton G, Posner J, Peck RW. The novel anti-migraine zolmitriptan (Zomig 311C90) has no clinically significant interactions with paracetamol or metoclopramide. EurJ Clin Pharmacol (1997) 53,229-34. 

---