Long-term administration of large doses of paracetamol impairs the reproductive competence of male rats.
OBJECTIVE
To evaluate the antireproductive effect of paracetamol in male rats.


METHODS
Male rats were orally administered daily with 500 mg/kg or 1000 mg/kg of paracetamol for 30 consecutive days. Their sexual behaviour and fertility were evaluated using receptive females.


RESULTS
At 2 h after treatment, sexual behaviour was not inhibited but on day 30 both doses of paracetamol caused marked impairment of libido (assessed by % mounting, % intromission and % ejaculation), sexual vigour (number of mounts and intromissions and copulatory efficiency) or sexual performance (intercopulatory interval). In mating experiments, the fertility (in terms of quantal pregnancy, fertility index, implantation index and number of implants) was significantly reduced. All these effects were reversible. The antireproductive effect was not due to a general toxicity but due to an increase in pre-implantation losses resulting from oligozoospermia, impairments of normal and hyper-activated sperm motility, and reduction in the fertilizing potential of spermatozoa.


CONCLUSIONS
Long-term use of high doses of paracetamol may be detrimental to male reproductive competence.
Ratnasooriya
W D
WD
Department of Zoology, University of Colombo, Colombo 3, Sri Lanka. dappvr@sltnet.lk
Jayakody
J R
JR
D000082:Acetaminophen / Q000008:administration & dosage*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003272:Contraceptive Agents, Male / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005298:Fertility / Q000187:drug effects* / Q000502:physiology; D005837:Genitalia, Male / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006062:Gonadotropins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018908:Muscle Weakness / Q000139:chemically induced; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism; D011453:Prostaglandins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012726:Sexual Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D013076:Sperm Count / Q000706:statistics & numerical data; D013081:Sperm Motility / Q000187:drug effects; D013312:Stress, Physiological / Q000139:chemically induced
D003272:Contraceptive Agents, Male; D006062:Gonadotropins; D011453:Prostaglandins; D009569:Nitric Oxide; D000082:Acetaminophen