All drugs are composed of chemical compounds, ranging from simple to complex molecules. While the majority of drugs are organic compounds, some are purely inorganic, such as lithium carbonate, ferrous sulphate, and magnesium hydroxide. Organic drugs can be weakly acidic (like aspirin and penicillin) or weakly basic (like morphine and chloroquine), or they can be nonelectrolytes (like alcohol and diethyl-ether). Most drugs are solid substances, such as paracetamol, propranolol, furosemide, and ampicillin, but some are in liquid forms, such as ethanol, glyceryl trinitrate, and propofol, and a few, like nitrous oxide, are gaseous.
The molecular weight of the majority of drugs falls between 100 and 1000 D, as molecules smaller than 100 D typically lack specific features that allow them to bind to closely related target biomolecules selectively. Larger molecules than 1000 D are unable to pass through membranes and barriers in the body to reach the target sites in various tissues and cells. However, some drugs are as small as lithium-ion (7D), while others, like heparin (10-20 KD), gonadotropins (>30 KD), enzymes, proteins, and antibodies (>50 KD), are much larger. Bulky molecule drugs have to be administered parenterally.
Drugs are generally considered foreign chemical substances (Xenobiotics) to the body. However, many endogenous chemicals, such as hormones, autacoids, metabolites, and nutrients, are also used as drugs. Chemical congeners of these metabolites and signal molecules are an important class of drugs that modify the synthesis, storage, degradation, or action of these metabolites and signal molecules.
Disclaimer: This article is for informational purposes only and should not be taken as medical advice. Always consult with a healthcare professional before making any decisions related to medication or treatment.