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The absorption of amorphous and polymorph A forms of chloramphenicol palmitate suspensions made with polysorbate 80 was investigated in children, rhesus monkeys, and cats. In children, both forms were absorbed. While polymorph A was absorbed at a slower rate, maintaining the blood level of chloramphenicol for 6 hr., the amorphous form was absorbed maximally at 2 hr. followed by a profound fall in the blood level. Although the absorption of the amorphous form was definitely superior, the polymorph A form in suspension with a surface-active agent was also absorbed to a considerable extent in children, maintaining blood levels of chloramphenicol for a prolonged period. In experiments with cats, polysorbate 80 increased the absorption of both forms of chloramphenicol palmitate, with the amorphous variety having superior absorption. In rhesus monkeys, there was little absorption of the polymorph A form of chloramphenicol palmitate in suspension, possibly indicating the absorption as species specific.

The in vitro release of pentaerythritol tetranitrate (PET) from a sustained-action PET tablet was determined using USP tablet disintegration apparatus with the modification that 100-mesh stainless steel wire cloth replaced the usual 10-mesh. The immersion medium was simulated gastric fluid for the first 2 hr. and simulated intestinal fluid for the subsequent 10 hr. There was a gradual release of the drug and 80 to 100% of the drug was dissoluted at the end of 12 hr. The tablet when administered by mouth to anesthetized cats produced a 28 to 30% fall in arterial blood pressure which persisted for 12 hr. A good correlation between the rate of release of the drug in vitro and the in vivo effect in sustained lowering of the blood pressure was obtained. The in vitro method described is proposed for the quality control of sustained-action PET tablets.