As to cimetidine (and some may think meto(clopramide) as well), I found the two articles that seem to me contradictory to what's described in PPH. Does anyone have any comments on this?
PPH says cimetidine should be used for reducing the gastric volume without (much) affecting pH, thus making SN absorbed in the blood stream more quickly. But the articles show meto is more effective for the purpose. It should also be noted that PPH previously encouraged high gastric pH and suggested the intake of sodium bicarbonate.
1.
Metoclopramide and cimetidine to reduce gastric fluid pH and volume
80 female patients undergoing outpatient laparoscopy were divided into four equal groups (20 per group) to investigate the effect of cimetidine and metoclopramide on the gastric fluid volume and pH.
Group I: 2 placebo tablets
Group II: 10 mg metoclopramide and 1 placebo tablet
Group III: 300mg cimetidine and 1 placebo tablet
Group IV: 10 mg metoclopramide and 300mg cimetidine
Results 2 hours after taking them
Gastric fluid volume and (pH)
I: 83.9 +/- 2.3 ml (1.38 +/- 0.12)
II: 11.1 +/- 0.63 ml (2.6 +/- 0.21)
III: 51 +/- 2.33 ml (4.04 +/- 0.32)
IV: 12.05 +/- 0.79 ml (4.64 +/- 0.28)
2.
The effects of intravenous cimetidine and metoclopramide on gastric volume and pH
The effects on gastric pH and volume of intravenous administration of cimetidine and metoclopramide before induction of anesthesia were studied. Sixty ASA Class I patients scheduled for elective surgery were randomly divided into four groups of 15 each, and the study was double-blinded. Group I received normal saline only; Group II received 4 mg/kg of cimetidine only; Group III received 0.15 mg/kg of metoclopramide only; and Group IV received 4 mg/kg of cimetidine and 0.15 mg/kg of metoclopramide. All drugs were given intravenously 30 min before induction of anesthesia. Gastric aspirates were collected during anesthesia, 30 min and 60 min after administration of the drugs.
Metoclopramide reduced gastric volume significantly when administered alone (P = 0.0001), but cimetidine did not (P = 0.10). Cimetidine increased the gastric fluid pH significantly (P = 0.0001) as did metoclopramide (P = 0.0023). The effects of cimetidine and metoclopramide on gastric fluid pH were additive when administered together. The combination of cimetidine and metoclopramide when given intravenously before anesthesia provides greater protection against aspiration pneumonitis in patients at risk than does either drug alone.