***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To determine contraceptive efficacy of hormonally induced sperm suppression to severe oligozoospermia or azoospermia .  DESIGN Prospect i ve , noncomparative contraceptive efficacy study . SETTING Multicenter study in 15 centers in nine countries . PARTICIPANTS Three hundred ninety-nine normal , healthy , fertile men requesting a male contraceptive method . INTERVENTION Weekly IM injection of 200 mg T enanthate . MAIN OUTCOME MEASURE Incidence of pregnancies in efficacy when couples relied on T injections alone for contraception . RESULTS Four pregnancies occurred during 49.5 person-years involving men with oligozoospermia ( 0.1 to 3 x 10(6)/mL ) and none during 230.4 person-years in azoospermic men : pregnancy rates 8.1 ( 95 percent confidence interval [ CI ] 2.2 to 20.7 ) and 0.0 ( 95 percent CI , 0.0 to 1.6 ) per 100 person-years , respectively , or 1.4 ( 95 percent CI , 0.4 to 3.7 ) per 100 person-years for oligozoospermia and azoospermia ( O to 3 x 10(6)/mL ) combined . Pregnancy rates were related to sperm concentration . Inadequate suppression of spermatogenesis occurred in eight men and escape from suppression occurred in four . Discontinuations were due to personal reasons ( 50 men , cumulative annual life-table rate 12.2 percent [ 95 percent CI , 9.1 percent to 16.1 percent ] ) and dislike of the injection schedule ( 21 men , 5.1 percent [ 95 percent CI , 3.2 percent to 7.9 percent ] ) . Thirty-five men discontinued for medical reasons ( 9.4 percent [ 95 percent CI , 6.7 percent to 13.2 percent ] ) , with no serious treatment-related side effects . After stopping injections , sperm output recovered ; additionally , fertility was demonstrated in 33 couples . CONCLUSION Suppression of spermatogenesis to azoospermia or severe oligozoospermia ( < or = 3 x 10(6)/mL ) induced by weekly T enanthate injections results in sustained , reversible contraception with good efficacy and minimal short-term side effects . New hormonal regimens with more convenient delivery and improved spermatogenic suppression would provide practical male contraception Following the intravasal injection of a new male contraceptive RISUG ( reversible inhibition of sperm under guidance ) in volunteers , routine semen analysis , semen biochemistry and germ cell morphology were evaluated in comparison with the corresponding preinjection sample s for a maximum period of 6 months . Sperm counts in all 25 subjects before injection varied from 45 to 120 x 10(6)/ml . Out of 25 subjects , 6 became azoospermic after 1 month , 15 after 2 months , 3 after 3 months and 1 after 4 months of contraceptive injection . The mean volume of the ejaculates was found to be less as compared to preinjection sample s. Occasional sperm or sperm heads and immature germ cells were identified in only a few postinjected subjects . However , no pregnancy was reported in these subjects during the study period . Abnormal morphology found in most of the sperm , but not in the accompanying immature germ cells , may be due to a charge-related effect on the former but not on the latter cells . Neutral alpha-glucosidase , the biochemical marker for epididymis , was estimated to be significantly lower in the seminal plasma of all the postinjected subjects . On the other h and , acid phosphatase activity and fructose levels in the seminal plasma were found to be in the normal range . Based on the above findings , it is concluded that at least for the present study period , RISUG , a new male contraceptive , is effective as a partially occluding agent in the vas deferens Following up on an earlier clinical trial demonstrating the safety of an intra-vas deferens injection of a contraceptive drug named Risug , comprised of styrene maleic anhydride ( SMA ) in a solvent vehicle of dimethylsulphoxide ( DMSO ) , a study to assess the contraceptive effectiveness of a specific dose ( 60 mg ) of SMA bilaterally was planned and implemented . Male subjects and their wives with normal reproductive profiles were the volunteer subjects . The wives were not using any contraceptives . The results reconfirm the safety and show that for a period of at least 1 year , the treatment leads to azoospermia in the male and gives pregnancy protection The safety and efficacy of gossypol continues to be controversial . The aim of this study was to evaluate gossypol as a contraceptive pill for men at doses lower than those previously prescribed and in men from various ethnic origin . A total of 151 men from Brazil , Nigeria , Kenya , and China were divided into two groups . Both groups received 15 mg gossypol/day for 12 or 16 weeks to reach spermatogenesis suppression . Subjects were then r and omized to either 7.5 or 10 mg/day for 40 weeks . In addition , 51 men were enrolled as a control group . In all , 81 subjects attained spermatogenesis suppression .  Only one man discontinued treatment because of tiredness . Potassium levels fluctuated within the normal range . FSH increased consistently . Testicular volume decreased , but after discontinuation , values returned to levels not statistically different from admission . Of 19 subjects on the 7.5 mg/day dose group , 12 recovered sperm counts > 20 million/mL within 12 months of discontinuing gossypol . In the 10 mg/day group , sperm counts recovered in only 10 of 24 subjects . Eight of the 43 patients remained azoospermic 1 year after stopping gossypol . All men diagnosed with varicocele failed to reverse spermatogenesis suppression . Gossypol blood levels indicated that sperm suppression occurs independently of concentration , whereas spermatogenesis recovery appears to be concentration-dependent . Gossypol may become a medical alternative to surgical vasectomy when the delay in onset of infertility is acceptable . When taken for 1 year , gossypol causes no reduction in sexual desire or frequency of intercourse . The possibility of reversal , occurring in 51 % of the men on this regimen within 1 year after stopping gossypol , is an advantage of this compound as compared with surgical sterilization in many parts of the world Earlier studies on the rat and the monkey had demonstrated that an injection of styrene maleic anhydride ( SMA ) in a solvent vehicle of dimethyl sulphoxide ( DMSO ) into the lumen of the vas deferens is toxicologically safe and has contraceptive action . Phase I clinical trial was therefore undertaken on 38 male volunteers giving varying doses of SMA , ranging between 5 mg and 140 mg , into each vas deferens . A dose of 70 mg is the predicted therapeutic dose based on animal data . That the compound is within the vas deferens lumen during the period of the safety assessment is inferred from the effect on the spermatozoa count in ejaculates which reach azoospermic levels in the higher dose ranges . The treatment is well tolerated with only minimal side effects in a few cases and no long-term adverse effects A r and omized controlled study was design ed to evaluate the merit of whether ingesting potassium salt or potassium ( K ) blocking agent while using gossypol contraceptive drug could alleviate the symptom of hypokalemia . Results indicate that K salt supplementation did not reverse the gossypol-related hypokalemia and that the blocking agent triamterene did not prevent loss of or enhance the retention of serum 
    Output:
    
Gossypol had problems with low efficacy and toxicity .
Although sperm density was lower among those taking Tripterygium , later reports indicated some toxicity .
At this time , no safe and effective  nonhormonal drug  is available for contraception in men .