Try the
Interactions Checker at Drugs.com.
The results are color coded as to the severity of the interaction (also includes drug-food interactions). The results are divided into description (the mechanism of the interaction - which can often be a bit complicated, what to monitor, what to avoid) and the management, which basically tells you what to do about the interaction. The results are only listed by generic name, so if you are unsure, you need to look up the name on the main database.
If you search on:
Lamictal,Ortho Tri-Cyclen,alcohol,multivitamin
the following results are produced:
ethanol (alcohol) and lamotrigine (Lamictal)
(moderate Drug-Drug)
Description:
GENERALLY AVOID:
Alcohol may potentiate some of the adverse effects of CNS-active agents. The combination may result in additive CNS-depression in general and
impairment of judgment, thinking, and motor skills.
MANAGEMENT:
Patients receiving CNS-active agents should be warned of this interaction and
advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid activities requiring mental alertness (e.g., driving or operating hazardous machinery) until they know how these agents affect them.
ethinyl estradiol-norgestimate (Ortho Tr-Cyclen) and lamotrigine (Lamictal)
(moderate Drug-Drug)
Description:
MONITOR:
Coadministration with estrogens and progestins may decrease the plasma concentrations and pharmacologic effects of lamotrigine in some patients. The mechanism is induction of lamotrigine glucuronidation by these hormones. One group of investigators cited seven suspected cases of this interaction in women treated with oral contraceptives that contained either ethinyl estradiol in combination with desogestrel or norethindrone or norethindrone alone. In these women, oral contraceptives reduced the plasma levels of lamotrigine by 41% to 64%, and a deterioration in seizure control was observed several days to two months after initiation of contraceptive use, necessitating an increase in lamotrigine dosage or discontinuation of the oral contraceptive. In some of the women, discontinuation of contraceptive use led to lamotrigine toxicity and necessitated the reduction of lamotrigine dosage. The interaction is further supported by the fact that changes in hormone levels are known to influence the pharmacokinetics of glucuronidated drugs in humans, and elimination of lamotrigine is significantly increased during pregnancy. However, a population pharmacokinetics study in patients newly diagnosed with epilepsy and receiving oral lamotrigine monotherapy for up to 48 weeks found no significant effect of oral contraceptive use or dose on the oral clearance of lamotrigine. Conversely, lamotrigine has been shown to have little or no effect on the pharmacokinetics of contraceptive hormones.
MANAGEMENT:
Pharmacologic response and
plasma lamotrigine levels should be monitored more closely whenever an oral contraceptive is added to or withdrawn from therapy, and the lamotrigine dosage adjusted as necessary. Patients should be advised to contact their physician if they experience loss of seizure control or symptoms of lamotrigine toxicity such as ataxia, nystagmus, increased seizures, irregular heartbeat, and changes in mental status.
ethanol (alcohol) and ethinyl estradiol-norgestimate (Ortho Tri-Cyclen)
(minor Drug-Drug)
Description:
The central nervous system effects and
blood levels of ethanol may be increased in patients taking oral contraceptives, although data are lacking and reports are contradictory. The mechanism may be due to enzyme inhibition. Consider counseling women about this interaction which is unpredictable.
ethinyl estradiol-norgestimate (Ortho Tri-Cyclen)
(minor Drug-Food)
Description:
The coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings,
grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.
ethanol (alcohol) and ethinyl estradiol-norgestimate (Ortho Tri-Cyclen)
(minor Drug-Drug)
Description:
The central nervous system effects and blood levels of ethanol may be increased in patients taking oral contraceptives, although data are lacking and reports are contradictory. The mechanism may be due to enzyme inhibition. Consider counseling women about this interaction which is unpredictable.
Which, in summary, means you need to avoid or limit alcohol, and make sure you tell your doctor about the Lamictal if ever you stop or change your oral contraceptive. 
lamictal 
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