Fun fact, xylazine in heroin was actually first seen more than 10 years ago, in Puerto Rico.
Xylazine is added because it is an alpha-2a agonist, which is an adrenaline
autoreceptor - it's what your body uses to sense adrenaline/noradrenaline levels. By activating this receptor it makes your body think "I have too much adrenaline floating around, I should release less to compensate", so it acts as a rapid-acting physical sedative that decreases blood pressure quite a lot, which would make your heroin or whatever seem more intense. Plus it has a short half life, and is readily diverted from veterinary supplies, and is not a controlled drug,
The closest analogue used in medicine would be
clonidine.
there is indeed a
test strip for xylazine available.
"tranq" is not xylazine specifically, rather a term for opioids with xylazine as a cut
Well, the thing is, xylazine can apparently be given by injection (IM/IV) in humans
[ref] However the list of side effects is a mile long and it is not used medically in humans for this reason. Its skin ulcerating effect is apparently due to reducing oxygenation in skin.
Wiki:
Xylazine administration can lead to diabetes mellitus and hyperglycemia. Other possible side-effects are areflexia, asthenia, ataxia, blurred vision, disorientation, dizziness, drowsiness, dysarthria, dysmetria, fainting, hyporeflexia, slurred speech, somnolence, staggering, coma, apnea, shallow breathing, sleepiness, premature ventricular contraction, tachycardia, miosis, and dry mouth. Rarely, hypotonia, urinary incontinence, and nonspecific electrocardiographic ST segment changes occur.
Chronic intravenous use of xylazine in combination with opioids is reported to be associated with physical deterioration, dependence, abscesses, and skin ulceration, sometimes progressing to necrosis with eschar formation, which can be physically debilitating and painful. Hypertension followed by hypotension, bradycardia, and respiratory depression lower tissue oxygenation in the skin. Thus, chronic use of xylazine can progress the skin oxygenation deficit, leading to severe skin ulceration. Lower skin oxygenation is associated with impaired healing of wounds and a higher chance of infection.[9] The ulcers may ooze pus and have a characteristic odor. In severe cases, amputations must be performed on the affected extremities.