Dinoprost Tromethamine
Dinoprost tromethamine is the tromethamine (THAM) salt of the naturally occurring **prostaglandin F2alpha (PGF2α)**. It is widely used in veterinary reproductive medicine across multiple species. * **Large Animals**: Primarily used as a luteolytic agent for estrous synchronization, treatment of unobserved (silent) estrus, pyometra, and as an abortifacient or parturition-inducing agent in cattle, horses, swine, and small ruminants. * **Small Animals**: Used off-label as an abortifacient and as an adjunctive medical therapy for open-cervix pyometra in dogs and cats. > **Clinical Pearl**: Dinoprost has a very narrow therapeutic index in dogs. The LD50 is only about 5 times the recommended therapeutic dose, making accurate dosing and careful monitoring critical. Newer protocols for pyometra often favor aglepristone combined with cloprostenol or misoprostol due to a better safety profile.
Mecanismo: Dinoprost acts directly as a **prostaglandin F2alpha (PGF2α)** analog. * **Luteolysis**: Binds to specific PGF2α receptors on the corpus luteum → inhibits steroidogenesis → induces structural and functional regression of the corpus luteum (luteolysis) → rapid decline in serum progesterone levels. * **Myometrial Contraction**: Directly stimulates myometrial smooth muscle activity → increases intracellular calcium → induces strong uterine contractions. * **Cervical Relaxation**: Promotes relaxation and dilation of the cervix, facilitating the expulsion of uterine contents (fetus or purulent material in pyometra).
Dosificación por especie
- Estrus synchronization · 8 mg IM on day 5 of estrous cycle and repeat in 11 days · IM · twice, 11 days apart · 11 days
- Abortifacient (first two months of pregnancy) · 10-15 mg IM · IM · once · once · Abortion takes place within 72 hours.
- Estrus synchronization · 8 mg IM on day 4 of estrous cycle and repeat in 11 days · IM · twice, 11 days apart · 11 days
- Pseudopregnancy (hydrometra/mucometra) · 5 mg IM once · IM · once · once
- Abortifacient · 5-10 mg IM throughout entire pregnancy · IM · once · once · Abortion takes place in 4-5 days.
- Induce parturition · 2.5-20 mg on days 144-149 · IM · once · once · Higher dosage (20 mg) yields more predictable interval to delivery.
- Treatment of pyometra · Initially 0.1 mg/kg SC, then 0.25 mg/kg SC once a day for 5 days · SC · once daily · 6 days total · Give bactericidal antibiotics concurrently. Not recommended in animals >8 yrs old.
- Abortifacient · 2 mg (total dose) per cat IM once a day beginning at day 33 · IM · once daily · Not specified · Side effects include prostration, vomiting and diarrhea.
Vías de administración
Contraindicaciones
- Pregnancy (unless abortion or induced parturition is desired)
- Intravenous (IV) administration
- Animals with bronchoconstrictive respiratory disease (e.g., asthma, 'heaves' in horses)
- Mares with acute or subacute disorders of the vascular system, GI tract, respiratory system, or reproductive tract
- Camelids (associated with acute toxicity and death)
- Relative contraindication: Closed-cervix pyometra
- Extreme caution in elderly (>8 years old) or debilitated animals, or those with severe cardiopulmonary, renal, or hepatic disease
Efectos adversos
- Dogs/Cats: Abdominal pain, emesis, defecation, urination, pupillary dilation followed by constriction, tachycardias, restlessness, anxiety, fever, hypersalivation, dyspnea, panting. Fatalities are possible (especially in dogs). Cats may exhibit intense grooming and vocalization.
- Cattle: Infection at injection site, salivation, hyperthermia (especially at higher doses).
- Swine: Erythema, pruritus, urination, defecation, slight ataxia, hyperpnea, dyspnea, nesting behavior, abdominal muscle spasms, tail movements, increased vocalization, salivation.
- Horses: Transient decreased body temperature, sweating. Less frequently: increased respiratory and heart rates, ataxia, abdominal pain, lying down.
Interacciones farmacológicas
- Other oxytocic agents · Activity may be enhanced by dinoprost.
- Progestins · Reduced effect of dinoprost would be expected with concomitant administration.
Monitoreo
- Cardiorespiratory effects (especially in dogs and cats, particularly after higher dosages)
- Adverse effects (vomiting, diarrhea, hyperthermia, distress)
- Efficacy of treatment (e.g., ultrasound for pyometra resolution or pregnancy termination, observation for estrus)
Sobredosis
Dogs are highly sensitive to the toxic effects of dinoprost. The LD50 in the bitch is reported to be **5.13 mg/kg SC**, which is only about 5 times greater than the recommended dose used by some clinicians. In large animals (cattle, swine, horses), overdose quantities (e.g., 5-10X recommended doses) result in exaggerated adverse effects such as hyperthermia, vomiting, and severe abdominal cramping. **Treatment**: If clinical signs are severe in any species, immediate supportive and symptomatic therapy is recommended.
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