Which factor does NOT affect the rate of drug absorption?

The rate of drug absorption can be influenced by various factors, but body weight does not directly affect the absorption process itself. Instead, factors like the pKa of the drug determine how well the drug can ionize in the body, which, in turn, influences its absorption across membranes. The solubility of the drug plays a crucial role as it affects how readily the drug can enter the systemic circulation; a drug that is poorly soluble may not be absorbed efficiently. The pH of the media, such as the gastrointestinal tract, also affects drug absorption since it can alter the ionization of the drug. In contrast, body weight might impact distribution and metabolism once the drug has been absorbed but does not directly influence the rate at which a drug is absorbed into the bloodstream.