Prazosin
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Prazosin
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| Systematic (IUPAC) name | |
| [4-(4-amino-6,7-dimethoxy-quinazolin-2-yl) piperazin-1-yl]-(2-furyl)methanone | |
| Identifiers | |
| CAS number | |
| ATC code | C02 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C19H21N5O4 |
| Mol. mass | 383.401 g/mol |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Protein binding | 97% |
| Metabolism | ? |
| Half life | 2–3 hours |
| Excretion | ? |
| Therapeutic considerations | |
| Pregnancy cat. |
? |
| Legal status | |
| Routes | Oral |
Prazosin, trade names Minipress,Vasoflex and Hypovase, is a medication used to treat high blood pressure (hypertension). It belongs to the class of alpha-adrenergic blockers, which lower blood pressure by relaxing blood vessels. Specifically, prazosin is selective for the alpha-1 receptors on vascular smooth muscle. These receptors are responsible for the vasoconstrictive action of norepinephrine, which in turn raises blood pressure. By blocking these receptors, prazosin reduces blood pressure.
Prazosin is orally active and has a minimal effect on cardiac function due to its alpha-1 receptor selectivity. Unlike other less selective alpha blockers that also block presynaptic alpha-2 receptors, it doesn't prevent inhibition of norepinephrine release. Uninhibited norepinephrine release usually causes an increased reflex tachycardia through the sympathetic baroreflex response that, in turn, increases cardiac output. However, when blood pressure drops, the body does not increase cardiac output to compensate for the loss in pressure when a person takes prazosin.
Prazosin is also useful in treating urinary hesitancy associated with prostatic hyperplasia by blocking alpha-1 receptors, which control constriction of both the prostate and ureters.
Side effects of prazosin include orthostatic hypotension, syncope, and nasal congestion. The orthostatic hypotension and syncope are associated with the body's poor ability to control blood pressure without active alpha-adrenergic receptors. Patients on prazosin should be told not to stand up too quickly, since their poor baroreflex may cause them to faint as all their blood rushes to their feet. The nasal congestion is due to dilation of vessels in the nasal mucosa. One phenomenon associated with prazosin is known as the "first dose response", in which the side effects of the drug, especially orthostatic hypotension, are especially pronounced after the first dose. Another common side effect of prazosin (and doxazosin) is priapism.[1][2].
This medication has shown to be effective in treating severe nightmares in children, associated with PTSD symptoms.[citation needed] Also veterans have been treated successfully at the Oregon VA for sleep disturbance related to PTSD. Doses are lower for this purpose than for control of blood pressure.[citation needed]
[edit] Prazosin in scorpion stings
Since 1983 prazosin has revolutionized the management of severe scorpion stings.[1]
[edit] References
- ^ Bawaskar HS, Bawaskar PH (Jan 2007). "Utility of scorpion antivenin vs prazosin in the management of severe Mesobuthus tamulus (Indian red scorpion) envenoming at rural setting". J Assoc Physicians India 55: 14–21. PMID 17444339.
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