This can lead to quite different Cp versus time results after oral administration. The t peak values are similar thus ka probably the same. C peak would show a good correlation with solubility. Use the potassium salt for better absorption orally. Use benzathine or procaine for IM depot use.
Some drugs exist in a number of crystal forms or polymorphs.
These different forms may well have different solubility properties and thus different dissolution characteristics. Chloramphenicol palmitate is one example which exists in at least two polymorphs. The recommendation might be that manufacturers should use polymorph B for maximum absorption. However, a method of controlling and determining crystal form would be necessary in the quality control process. Aguiar, A.J., Krc, J., Kinkel, A.W., and Samyn, J.C. 1967.