Testosterone esters were synthesized for the first time in 1936, and were found to have greatly improved potency relative to testosterone.  Among the esters synthesized, testosterone propionate was the most potent, and for this reason, was selected for further development, subsequently being marketed.  Testosterone propionate was introduced in 1937 by Schering AG in Germany under the brand name Testoviron.  It was the first ester of testosterone to be introduced,  and was the major form of testosterone used medically before 1960.  In the 1950s, longer-acting testosterone esters like testosterone enanthate and testosterone cypionate were introduced and superseded testosterone propionate.  Although rarely used nowadays due to its short duration,  testosterone propionate remains medically available. 
Fluid and electrolyte disturbances: Retention of sodium, chloride, water, potassium, calcium, and inorganic phosphates.
Gastrointestinal: Nausea, cholestatic jaundice, alterations in liver function tests, rarely hepatocellular neoplasms and peliosis hepatis (see WARNINGS ).
Hematologic: Suppression of clotting factors II, V, VII, and X, bleeding in patients on concomitant anticoagulant therapy, and polycythemia.
Nervous system: Increased or decreased libido, headache, anxiety, depression, and generalized paresthesia.
Allergic: Hypersensitivity, including skin manifestations and anaphylactoid reactions.
Vascular Disorders: venous thromboembolism
Miscellaneous: Inflammation and pain at the site of intramuscular injection.
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.