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Cabergoline: long-acting oral treatment of hyperprolactinemic disorders.

Cabergoline, a new orally active dopaminergic drug with an extremely long-lasting PRL-lowering effect, was given to 48 hyperprolactinemic women for 3-18 months (median, 8 months) at doses varying between 0.2-3 mg/week administered one to three times weekly. Serum PRL levels declined to normal in 41 women, 30 of whom received 0.2-1 mg cabergoline once weekly, 8 received 0.2-0.5 mg twice weekly, and 3 received 0.4-0.6 mg 3 times weekly. Five women had slightly supranormal serum PRL levels while receiving 0.3-0.6 mg once weekly, but the dose was not increased because the lower dose had produced the desired clinical benefit. Two women had 50% reductions in their serum PRL levels, but remained hyperprolactinemic while receiving 2-3 mg cabergoline weekly. Among 30 amenorrheic women, 28 had resumption of menses, the exceptions being 2 hypopituitary women, presumptive evidence of ovulation was available in 21. Marked tumor shrinkage occurred after 3-month treatment in 5 of the 6 women who had macroprolactinomas. Only 4 women had side-effects during the first weeks of treatment, and these vanished despite continued cabergoline administration at the same or reduced, but still effective, doses. In a short term, double blind study, cabergoline at 3 different schedules (0.4 mg twice weekly, 0.2 mg 4 times weekly, and 0.4 mg 3 times weekly for 3 weeks, followed by 0.4 mg twice weekly) or placebo was given to a total of 24 hyperprolactinemic women (6 in each subgroup) for 8 weeks, with weekly evaluation of serum PRL levels and side-effects. All 3 cabergoline schedules, but not placebo, induced significant reductions in serum PRL concentrations during the 8-week treatment period. Mild transient side-effects occurred in 7 drug-treated patients (nausea in 5; dizziness in 3). We conclude that cabergoline is effective treatment for hyperprolactinemia. Its efficacy, tolerability, and long duration of action may make it the drug of choice for patients with hyperprolactinemia.

Administration, Oral↗

Treatment of prolactin-secreting macroadenomas with the once-weekly dopamine agonist cabergoline.

Dopamine agonist administration is the primary therapy for macroprolactinomas, but bromocriptine is the only agent approved in the United States. Its use is limited by a high incidence of side effects, a short duration of action, and a lack of effectiveness in some patients. Cabergoline is a long-acting dopamine agonist specific for the D2 receptor that is more effective and better tolerated than bromocriptine in women with microadenomas or idiopathic hyperprolactinemia. However, experience with cabergoline in the treatment of patients with macroadenomas is limited. We report the first study of chronic administration of cabergoline conducted exclusively in patients with macroprolactinomas. Fifteen patients (8 women, 7 men) ages 18-76 yr were studied in an open-label 48-week dose escalation trial of cabergoline administered once per week. Eleven patients had received prior therapy with other dopamine agonists. Mean prolactin (PRL) levels decreased by 93.6%, and normal levels were attained in 73% of patients at doses of 0.5-3.0 mg per week. Three of five patients who had failed to normalize PRL on prior dopamine agonists achieved normal levels. Gonadal function was restored in all hypogonadal men and in 75% of premenopausal women with amenorrhea. Tumor size decreased in 11 of the 15 patients. Side effects were minimal. Of the 5 patients who had experienced side effects in prior dopamine agonists, 4 had none on cabergoline, and the fifth had milder symptoms. During two further years of follow up, the improvement in PRL levels, gonadal function, and tumor size has persisted during cabergoline administration, and three patients have experienced a further decline in PRL and/or tumor size. This study demonstrates the effectiveness and minimal side effects of once-weekly cabergoline for treatment of macroprolactinomas.

Adenoma↗

Multicenter, placebo-controlled trial of cabergoline taken once daily in the treatment of Parkinson's disease.

Cabergoline is a dopaminergic agonist relatively specific for the D2 receptor and much longer-acting than other dopamine agonists. We conducted a randomized, placebo-controlled, double-blind study of cabergoline in 188 levodopa/carbidopa-treated patients with suboptimally controlled Parkinson's disease (PD). The cabergoline patients had significantly better Activities of Daily Living (p = 0.032) and Motor Examination (p = 0.031) scores at the conclusion of the trial compared with the placebo group. The daily levodopa dose for the cabergoline patients decreased 18% compared with a 3% reduction for the placebo group (p < 0.001). The amount of time in the "on" state increased more in the cabergoline group (p = 0.022). The side-effect was similar to that seen with other dopamine agonists, and cabergoline was generally well tolerated. We conclude that cabergoline is an effective adjunct to levodopa for the treatment of PD.

Activities of Daily Living↗

Prevention and termination of pregnancy in rats by cabergoline, a dopamine agonist.

The objective of the study was to clarify the potency and action of cabergoline, a dopamine agonist, in preventing and terminating pregnancy in rats. Cabergoline administered s.c. to female rats on days 1, 2 and 3 of pregnancy prevented implantation of the fertilized ova and development of the embryos. The drug was 100% effective at doses of 10 micrograms kg-1 day-1 or higher. Serum progesterone determined on day 8 of pregnancy was significantly reduced in rats treated with cabergoline at doses of 5 micrograms kg-1 day-1 and higher, whereas serum concentrations of oestradiol remained unchanged. Cabergoline at doses of 10 and 20 micrograms kg-1 day-1 administered s.c. on days 7, 8 and 9 of pregnancy was partially effective (43 and 50%, respectively) in terminating pregnancy, whereas at doses of 30 micrograms kg-1 day-1, and higher, pregnancy was terminated in all treated rats. Serum concentrations of progesterone on days 12 and 16 of pregnancy were significantly lower in rats treated with doses of 10 micrograms kg-1 day-1 or higher. Serum prolactin determined on day 4 of pregnancy in rats treated with cabergoline at the effective dose of 10 micrograms kg-1 day-1 on days 1, 2 and 3 of pregnancy was significantly reduced to 1.7 +/- 0.62 ng ml-1 from a pretreatment value of 16.0 ng ml-1. The lowest effective dose of cabergoline in reducing serum prolactin determined on day 8 of pregnancy was 20 micrograms kg-1 day-1. The present results support the hypothesis that cabergoline acts by inhibiting prolactin production or release, thereby inhibiting progesterone biosynthesis by the ovary.

Animals↗

Cabergoline, pramipexole and ropinirole used as monotherapy in early Parkinson's disease: an evidence-based comparison.

Dopamine agonists have been widely used as add-on to levodopa in the treatment of Parkinson's disease with motor fluctuations. However, the use of dopamine agonists in early Parkinson's disease and levodopa-naive patients is controversial. Although dopamine agonists have been compared with levodopa, no studies exist which directly compare one dopamine agonist with another. This evidence-based review compares the results of large published studies of early treatment of Parkinson's disease with dopamine agonists (cabergoline, ropinirole or pramipexole) with similar studies using levodopa. Because of their design, the common variables analysed in all studies were the proportion of patients who developed dyskinesia, those withdrawn from the trial and the mean change from baseline in Unified Parkinson's Disease Rating Scale (UPDRS) parts II and III scores. Cabergoline, pramipexole and ropinirole were similarly effective in reducing the risk for dyskinesia relative to levodopa (p < 0.01 for all three). The reduction in risk for dyskinesia was slightly more evident for pramipexole and ropinirole (p < 0.0001) than cabergoline (p = 0.0074). Odds ratios (95% confidence intervals [CI]) relative to levodopa were 0.38 (0.19-0.78) for cabergoline, 0.25 (0.13-0.47) for pramipexole and 0.31 (0.18-0.53) for ropinirole. The absolute risk reductions (95% CI) were, respectively, 8% (2.2-13.7), 20% (11.7-29.8) and 25% (13.6-36.7), ropinirole reducing the risk significantly more than cabergoline. The mean change from baseline UPDRS was similar for pramipexole and ropinirole (not evaluated for cabergoline). The proportion of withdrawn patients and the adverse effect profiles of the three agonists were similar to each other, with the exception of oedema, which was less prominent for ropinirole than for the other two agonists. Cabergoline, pramipexole and ropinirole are comparable choices for the delay of dyskinesia. Their adverse effect profiles are also similar, but they are less well tolerated than levodopa. The motor antiparkinsonian benefit of dopamine agonists is somewhat smaller than that of levodopa.

Age of Onset↗

Treatment of Japanese restless legs syndrome patients with cabergoline: an open clinical preliminary trial.

OBJECTIVE: To determine the effective dose of cabergoline in Japanese patients with restless legs syndrome (RLS). METHODS: Six cases of idiopathic RLS and three of RLS with Parkinson disease (PD) participated in an open clinical preliminary trial. All cases were diagnosed based on the clinical criteria of the International RLS Study Group. Three RLS cases (1.3%) were detected out of 229 consecutive cases with PD. RLS severity was evaluated with International RLS Study Group (IRLSSG) Rating Scale Version 2.2 before and one year after the treatment with cabergoline. RESULTS: For 6 idiopathic RLS patients, the IRLSSG questionnaire scores improved from 25.5+/-3.7 to 10.7+/-8.9 (p=0.028, Wilcoxon test) with 1 mg of daily cabergoline at the endpoint. For 3 RLS cases with PD, the score was 21.7+/-3.7 before the treatment, and RLS symptoms completely disappeared with 1 mg of cabergoline. One of RLS cases with PD required additional cabergoline later because of parkinsonism. No adverse event with cabergoline was reported in this study. CONCLUSION: One mg of daily cabergoline is effective in some Japanese patients of RLS.

Aged↗

Treatment of idiopathic restless legs syndrome (RLS) with the D2-agonist cabergoline--an open clinical trial.

STUDY OBJECTIVES: To define the effective dose of cabergoline and to evaluate the tolerability and efficacy of cabergoline in patients with restless legs syndrome (RLS). DESIGN: Treatment of idiopathic RLS patients with cabergoline in a 12-week open label trial. Patients on levodopa therapy were allowed to either stop levodopa prior to study entry or to continue, taper or discontinue levodopa during the study. Efficacy parameters were assessed by polysomnography and subjective ratings at baseline and at week 12. Primary efficacy parameters were the number of PLM and total sleep time. SETTING: Dept. of Neurology, Sleep Disorders Center PATIENTS: Nine patients with moderate to severe RLS (age 38.1 to 64.3 years, mean 54.1 years) who had experienced insufficient benefit under levodopa therapy and/or in part developed daytime augmentation participated. At study entry five patients were still under levodopa therapy (400-800 mg). INTERVENTIONS: Up-titration of cabergoline (single evening dose) until RLS symptoms clearly improved. Initial comedication with domperidone 20 mg t.i.d. MEASUREMENTS AND RESULTS: At the endpoint all patients were on cabergoline monotherapy (mean dosage 2.1 mg, range 1 to 4 mg). Domperidone was stopped in all patients due to good tolerability. Polysomnographic data showed a significant reduction of the number of periodic leg movements (PLM) (195.8+/-109.1 (baseline) vs. 26.4+/-40.2 (12 weeks cabergoline monotherapy; p=0.002), PLM arousals (51.7+/-42.3 vs. 6.4+/-11.2; p=0.017) and PLM awakenings (10.4+/-7.8 vs. 1.0+/-1.7; p=0.001). Total sleep time was prolonged (302.7+/-50.7 vs. 379.4+/-59.8 min; p=0.018), sleep latency shortened (42.4+/-49.1 vs. 16.3+/-22.8 min; p=0.214) and sleep efficiency increased (63.1+/-10.5 vs. 79.1+/-12.5%; p=0.017). All patients reported a impressive relief or became free of RLS symptoms. CONCLUSION: Cabergoline is effective and well tolerated in restless legs syndrome especially in patients with severe RLS and those who developed augmentation under levodopa therapy.

Adult↗

Treatment of Parkinson's disease and restless legs syndrome with cabergoline, a long-acting dopamine agonist.

Dopamine agonists have diverse chemical and physical properties that can directly stimulate the dopamine receptors, unlike levodopa which undergoes presynaptic breakdown to dopamine before dopaminergic effects in Parkinson's disease (PD). Cabergoline, a dopamine agonist effective given once daily, is being used as treatment for PD. In theory, therapy with cabergoline provides striatal intrasynaptic dopamine replacement of PD in a physiological manner because of its long half-life and the resultant sustained rather than pulsatile dopaminergic stimulation. Several placebo-controlled trials using cabergoline as adjunctive therapy in PD have shown that cabergoline significantly reduces 'off' time, improves motor function and reduces levodopa requirement. Cabergoline has also been used as monotherapy in PD and has been shown to be as effective as other dopamine agonists in improving motor function and to be superior to levodopa in reducing dyskinesias over a five-year period. Work from our group and others have also demonstrated the efficacy of cabergoline in PD patients with nocturnal disabilities and those with restless legs syndrome (RLS). More recently we have reported that cabergoline is a well-tolerated dopamine agonist in both young and elderly patients and has an acceptable side-effect profile.

Aged↗

Lack of pharmacokinetic interaction between the selective dopamine agonist cabergoline and the MAO-B inhibitor selegiline.

The addition of a dopamine agonist and of a monoamine oxidase type B inhibitor to I-dopa has been suggested in the therapy of Parkinson's disease. The plasma pharmacokinetics of both cabergoline and I-dopa have previously been shown to remain unaffected when the two drugs are given concomitantly. This study aimed at examining whether the plasma pharmacokinetic parameters of cabergoline and selegiline are modified when given in combination. Selegiline is hardly detectable in plasma. Therefore, the plasma levels of its metabolites amphetamine, methamphetamine and desmetylselegiline were used to assess the effect of cabergoline co-administration. Plasma levels of the selegiline metabolites were determined first after selegiline administration (10 mg/day) for 8 days, and then after administration of both drugs for 22 additional days (day 30). Cabergoline plasma levels were measured on day 30, and then after administration of cabergoline (1 mg/day) alone for further 22 days. No statistical difference was found between the Cmax.ss, tmax.ss, AUC0-24h.ss, C0h.ss, C24h.ss values of cabergoline and of the selegiline metabolites when the two drugs were given alone or in combination, indicating the absence of pharmacokinetic interaction between cabergoline and selegiline.

Aged↗

[Cabergoline in the inhibition of lactogenesis and suppression of lactopoiesis].

INTRODUCTION AND AIMS: 1) Evaluate the capacity of cabergoline to inhibit lactogenesis by the administration of a single dose of 1 mg within 24 h of birth, primary inhibition. 2) Evaluate the capacity of cabergoline to suppress lactopoiesis (lactation) by the administration of 0.25 mg twice a day for 2 days, secondary inhibition. 3) Evaluate the collateral effects of cabergoline at these two doses. 4) Evaluate the reduction rate of prolactin (PRL) at 4 and 14 days after cabergoline administration. EXPERIMENTAL PROTOCOL: A prospective study was performed from 1/2/1995 to 31/1/1996 in 100 puerperae with indications for lactation with follow-up at 4 and 14 days after drug administration. The study was performed in the Division of Gynecology and Obstetrics of Sanremo Hospital in collaboration with the Analysis Service. RESULTS: Cabergoline inhibited primary and secondary lactation in all the puerperae examined. In 92% of cases lactation was suppressed following a single dose whereas a second treatment cycle was required in 8%. Twenty-two cases reported slight collateral effects without the need to resort to additional treatment. In 4 cases the collateral effects were of moderate intensity and it was necessary to administer symptomatic treatment. Mean levels of serum PRL at 4 and 14 days after cabergoline administration were respectively 12.5 and 18.2 ng/ml. CONCLUSIONS: Cabergoline, a new dopaminergic drug with long-term inhibition of PRL production and secretion, can inhibit lactogenesis and lactopoies in 92% of cases at a dose of 1 mg; it can reduce long-term PRL levels (18.2 ng/ml) and in 4% it is necessary to resort to symptomatic treatment of the undesirable effects caused.

Cabergoline↗

The effect of food on cabergoline pharmacokinetics and tolerability in healthy volunteers.

The effect of food on the pharmacokinetics and tolerability of cabergoline in man was investigated. For this purpose an open, randomized, single-dose study was conducted in 12 healthy male volunteers who received 1 mg cabergoline as tablets both under fasting conditions and after a breakfast containing a substantial amount of carbohydrates, fat, and proteins, in a crossover fashion. The two treatments were separated by a 4 week washout period. Plasma and urine were collected up to 336 and 168 h respectively after administration and cabergoline concentration was measured in both fluids using a validated radioimmunoassay. Tolerability assessment included haematology, blood chemistry, and urinalysis, blood pressure and heart rate measurements, and ECG. Under both fasting and fed conditions low but persistent cabergoline plasma levels were observed in the present study up to 2 weeks after drug intake, in agreement with the long-lasting prolactin-lowering activity of the drug. In subjects receiving cabergoline under fed or fasting conditions, Cmax values averaged 44 and 54 pg mL(-1), AUC(0-336 h) averaged 6392 and 5331 pg h mL(-1), Ae(0-168 h) averaged 12.7 and 11.9 micrograms, and t1/2 averaged 109.7 and 101.3 h, respectively. No statistically significant difference was found when Cmax, AUC(0-336 h), t1/2, and Ae(0-168 h) from subjects treated under fasting and fed conditions were compared. Median tmax values in subjects treated under fasting or fed conditions were identical (2.5 h). The statistical analysis applied to the parameters chosen to evaluate the variations in the blood pressure profiles observed either supine or standing did not show any significant difference between the fed and fasting conditions. Heart rate values were not significantly modified after cabergoline under either fed or fasting conditions. Laboratory evaluation showed some minor deviations from normal, which were not clinically relevant (only one subject showed an occasional and transient elevation in alkaline phosphatase which disappeared in the subsequent laboratory evaluations) and were considered for the most part not to be drug related. Eleven subjects reported adverse events (one after both treatments, five only after drug intake under fasting conditions, and five only after drug intake with food.

Adult↗

Cabergoline versus levodopa monotherapy: a decision analysis.

We evaluated the incremental cost-effectiveness of cabergoline compared with levodopa monotherapy in patients with early Parkinson's disease (PD) in the German healthcare system. The study design was based on cost-effectiveness analysis using a Markov model with a 10-year time horizon. Model input data was based on a clinical trial "Early Treatment of PD with Cabergoline" as well as on cost data of a German hospital/office-based PD network. Direct and indirect medical and nonmedical costs were included. Outcomes were costs, disease stage, cumulative complication incidence, and mortality. An annual discount rate of 5% was applied and the societal perspective was chosen. The target population included patients in Hoehn and Yahr Stages I to III. It was found that the occurrence of motor complications was significantly lower in patients on cabergoline monotherapy. For patients aged >/=60 years of age, cabergoline monotherapy was cost effective when considering costs per decreased UPDRS score. Each point decrease in the UPDRS (I-IV) resulted in costs of euro;1,031. Incremental costs per additional motor complication-free patient were euro;104,400 for patients <60 years of age and euro;57,900 for patients >/=60 years of age. In conclusion, this decision-analytic model calculation for PD was based almost entirely on clinical and observed data with a limited number of assumptions. Although costs were higher in patients on cabergoline, the corresponding cost-effectiveness ratio for cabergoline was at least as favourable as the ratios for many commonly accepted therapies.

Antiparkinson Agents↗

Combined effects of cabergoline and L-dopa on parkinsonism in MPTP-treated cynomolgus monkeys.

The behavioral effects of L-dopa or cabergoline alone were compared with those of the joint administration of the two drugs in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned parkinsonian cynomolgus monkeys with attention to the induction of hyperactivity and dyskinesia. Cabergoline alone at 0.2 mg/kg or less improved in a dose-dependent fashion the parkinsonism without inducing hyperactivity and dyskinesia following a single subcutaneous injection. L-dopa alone improved the parkinsonism, but induced hyperactivity and dyskinesia, depending on the dose applied. Doses required for 50% amelioration by L-dopa and cabergoline were 10 and 0.038 mg/kg, s.c., respectively. With low doses (50%-amelioration doses), cabergoline or L-dopa alone improved the parkinsonism without induction of hyperactivity and dyskinesia, but the duration of action was brief. Cabergoline in combination with L-dopa was highly effective in improving motor disability without induction of hyperactivity and dyskinesia. Moreover, the duration of action was more prolonged with the coadministration than with the single administration of each drug. These findings suggest that the combined therapy with low doses of L-dopa and cabergoline is beneficial for treating patients with advanced Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

Complete remission of Nelson's syndrome after 1-year treatment with cabergoline.

In this case report we demonstrated that treatment with the long-acting D2 receptor agonist cabergoline for 1 year induced normalization of plasma ACTH levels and disappearance of the pituitary tumor in a patient with Nelson's syndrome. A young man underwent bilateral adrenalectomy and subsequent pituitary irradiation for Cushing's disease after unsuccessful neurosurgical treatment. Thereafter, he was given cortisone acetate replacement at the dose of 62.5 mg a day. Fifteen months after pituitary irradiation, he developed Nelson's syndrome, having skin hyperpigmentation, high plasma ACTH levels (376 ng/l) and a pituitary microadenoma (5 mm) documented at magnetic resonance imaging (MRI) of the pituitary region. After 6 months of cabergoline treatment, given at the dose of 1 mg a week, plasma ACTH levels were significantly decreased (from 376 to 113 ng/l) but they were not normalized. Cabergoline dose was then increased up to 2 mg a week. Six months later plasma ACTH levels were normalized (22 ng/l) and MRI demonstrated the disappearance of the pituitary adenoma. In order to investigate on the direct effect played by cabergoline treatment on the remission of Nelson's syndrome, the treatment was withdrawn. Plasma ACTH levels significantly increased (119 ng/l) after 3 months of treatment withdrawal. At the last follow-up, during cabergoline treatment at the dose of 2 mg/week plasma ACTH levels were normalized (40.4 ng/l). This case demonstrated that cabergoline treatment is able to induce the remission of Nelson's syndrome and may be a valid therapeutic alternative in this syndrome.

Adenoma↗

Effect of cabergoline added to levodopa treatment on sleep-wake cycle in idiopathic Parkinson's disease: an open label 24-hour polysomnographic study.

Few studies focused on the effects of cabergoline on sleep-wake cycle in PD. Twelve patients affected by PD treated with levodopa as monotherapy underwent two 24-hour ambulatory polysomnographic (A-PSG) sessions twice: in baseline condition (levodopa as monotherapy) and after addition of cabergoline. In each condition, a subjective evaluation of sleep quality and daytime sleepiness was obtained by means of Parkinson's disease Sleep Scale (PDSS) and the Epworth Sleepiness Scale. The statistical analysis of sleep parameters revealed a significant increase of sleep efficiency and slow wave sleep under cabergoline. The PDSS total score showed a significant improvement of overall sleep quality after cabergoline. No significant changes in daytime sleepiness were observed. No patient referred and/or showed sleep attacks before and after addition of cabergoline. We hypothesize that the long-lasting effect of cabergoline may improve the objective quality of nocturnal sleep in PD patients complaining nocturnal motor disability without inducing daytime sleepiness.

Aged↗

Induction of abortion in queens by administration of cabergoline (Galastop) solely or in combination with the PGF2alpha analogue Alfaprostol (Gabbrostim).

The efficacy of cabergoline solely or combined with a PGF2alpha analogue in inducing abortion at different stages of pregnancy was investigated in 18 queens. The queens were assigned to two treatments: Group I ( n=10 )-cabergoline (15 microg/kg; daily, orally) and Group II ( n=8 )-cabergoline (15 microg/kg; daily, orally) combined with alfaprostol (10 microg/kg; every other day, subcutaneously). Each group was divided into two subgroups according to the duration of pregnancy when treatments started: Group IA ( n=8 ) included queens from Days 34 to 42 after mating. Group IB cats ( n=2 ) started treatments on Day 45 post-mating. Similarly, the combination of cabergoline and PGF2alpha analogue was first given to Group IIA ( n=6 ) from Days 25 to 40 of pregnancy and to Group IIB ( n=2 ) on Days 45 and 47, respectively. Termination of pregnancies was successful in all cats of Group IA, while treatments failed in both cats of Group IB, even though seven and eight treatments, respectively, were given. Mean (+/-S.D.) plasma progesterone concentrations before the start of treatments were 85.0+/-12.3 nmol/l and decreased within 3 days to 8 nmol/l and subsequently to basal values, when the queens aborted (Group IIA, n=6 ) or gave birth prematurely (Group IIB, n=2 ). When abortions failed (Group IB, n=2 ), progesterone concentrations remained elevated (16.9 and 9.8 nmol/l). Duration of combined therapy during late pregnancy in Group IIB ( n=2 ) lasted about 10 days. In both cases, premature birth occurred and the kittens died within 16 h after birth. Overall, treatments starting on Days 25-42 of pregnancy (Groups IA and IIA) had abortion rates of 100%. The average duration of treatments was 5.6+/-1.5 days (range, 3-8). Side effects seen were vomiting and occurred in 6 of the 109 (5.5%) treatments. In conclusion, pregnancies were successfully terminated in the second trimester of feline pregnancy by daily application of cabergoline solely or combined with the PGF2alpha analogue alfaprostol (given every other day). Cabergoline alone was ineffective in inducing abortion at later stages of pregnancy.

Abortion, Induced↗

Effect of stage of anestrus on the induction of estrus by the dopamine agonist cabergoline in dogs.

Beagle bitches were administered the dopamine D2 receptor agonist cabergoline in 3 groups of 5 animals each, starting on known days of the estrous cycle. Cabergoline treatment was started in either early anestrus (Days 93 to 108), mid-anestrus (Days 123 to 156), or late anestrus (Days 161 to 192) at doses of 5 ug/kg/d, per os, and was continued until the confirmation of induced proestrus or for 40 d. Reproductive parameters were compared with those in 5 control anestrous bitches (Days 90 to 150). In control bitches, the mean (+/- SEM) interval to the next proestrus (73+/-11 d) resulted in an interestrus interval (192+/-9 d) similar to that of the previous cycles (196+/-11 d). In 14 of the 15 cabergoline-treated bitches, the next proestrus occurred within 4 to 30 d, was premature in early and mid-anestrous bitches and developed with low variability within groups. The resulting intervals to proestrus in bitches treated with cabergoline in early anestrus (20+/-2 d), mid-anestrus (14+/-3 d) and late anestrus (6+/-1 d) resulted in interestrus intervals in those groups of 131+/-5, 166+/-7 and 196+/-2 d, respectively. In response to treatment, interestrus intervals were reduced (P<0.05) and more synchronous (P<0.05) in early and mid-anestrus bitches, and were more synchronous (P<0.05) in late-anestrous bitches compared with those of control bitches or those of the previous cycle. Periovulatory estradiol and progesterone profiles of induced cycles in treated bitches were similar to those of spontaneous cycles in control bitches. Four of 5 control bitches and 12 of the 14 responding cabergoline-treated bitches became pregnant and produced normal litters. Plasma prolactin concentrations at Days 2 and 5 of treatment (0.3+/-0.1 ng/mL) and at the onset of proestrus shortly before the end of treatment (0.4+/-0.1 ng/mL) were lower (P<0.05) than those present in anestrus prior to treatment (1.7+/-0.6 ng/mL) or in control bitches. Prolactin was also low at the onset of proestrus in control bitches (0.5+/-0.2 ng/mL). The results demonstrate that prolactin-lowering doses of the dopamine agonist cabergoline can terminate the normal obligate anestrus in dogs, and that the effect occurs more slowly in early anestrus than in mid or late anestrus.

Anestrus↗

In vivo investigation of luteal function in dogs: effects of cabergoline, a dopamine agonist, and prolactin on progesterone secretion during mid-pregnancy and -diestrus.

The role of prolactin on luteal function in dogs was investigated in vivo. The function of prolactin in mid-luteal phase was compared in pregnant and nonpregnant dogs. A dopamine agonist, cabergoline, known for its prolactin secretion inhibitory effects, was injected subcutaneously at a dose of 5 micrograms/kg body weight in five pregnant and five nonpregnant Beagle bitches. Mean plasma prolactin and progesterone were dramatically suppressed for 4 to 5 days after injection in both groups when compared with control pregnant and non-pregnant animals, whereas no effect on luteinizing hormone (LH) secretion was observed. The decline in plasma progesterone occurred after that in prolactin, suggesting plasma progesterone was impaired by inhibition of prolactin secretion. These results confirm the luteotropic importance of prolactin in pregnant bitches, and also demonstrate its importance in luteal phase of the nonpregnant dog. Second, to demonstrate that the effects of cabergoline were mediated by prolactin inhibition and not by a direct action on the corpus luteum, concomitant administration on Day 30 of cabergoline and prolactin (375 micrograms i.v. twice daily on Days 30 and 31) or cabergoline and LH (750 micrograms i.v. twice daily on Days 30 and 31) was affected in two groups of five pregnant animals each. Results showed that only prolactin was able to reverse the negative effects of cabergoline on circulating progesterone. This confirms the indirect mode of action of the dopamine agonist, cabergoline on corpus luteum function. Third, further investigation on the precise luteotropic role of prolactin was made by IV injection of 375 micrograms pure canine prolactin twice daily in five pregnant bitches on Days 30 and 31, and in five pregnant bitches on Days 40 and 41. No direct stimulatory effect of prolactin on plasma progesterone secretion occurred. Nor was there a noticeable effect on plasma LH secretion. These results suggest that prolactin is unable to directly stimulate progesterone secretion by the corpus luteum of pregnancy. The results of this study suggest that prolactin is an essential luteotropin in the dog from mid-luteal phase in both pregnant and nonpregnant animals. However, it appears to act by sustaining corpus luteum lifespan and function rather than by direct stimulatory effects on progesterone secretion.

Animals↗